Technical Guidelines for the Implementation of


The Advanced National Seismic System—Version 1.0


Prepared by ANSS Technical Integration Committee 

Open-File Report 02-92


U.S. DEPARTMENT OF THE INTERIOR 

U.S. GEOLOGICAL SURVEY 
Technical Guidelines for the Implementation of 

The Advanced National Seismic System—Version 1.0 

Prepared by ANSS Technical Integration Committee1 

Open-File Report 02-92 

2002


This report is preliminary and has not been reviewed for conformity with U.S. Geological Survey 

editorial standards or with the North American Stratigraphic Code. Any use of trade, firm, or product 

names is for descriptive purposes only and does not imply endorsement by the U.S. Government. 

U.S. DEPARTMENT OF THE INTERIOR 

U.S. GEOLOGICAL SURVEY 

1Members listed in Appendix A 
ANSS TG v 1.0 

1 INTRODUCTION............................................................................................................................... 1 


1.1 OVERVIEW ................................................................................................................................... 1 


1.2 VOCABULARY............................................................................................................................... 3 


1.3 EXISTING SEISMIC NETWORK SITUATION..................................................................................... 4 


1.4 BASICS OF THE ANSS ORGANIZATION ....................................................................................... 6 


1.5 EVOLUTION OF THE TECHNICAL GUIDELINES ........................................................................... 10 


2 NETWORK ARCHITECTURE AND INTERCONNECTION ................................................... 11 


2.1 OVERALL ORGANIZATION .......................................................................................................... 11 


2.2 GENERAL ISSUES AND RECOMMENDATIONS ............................................................................ 13 


2.3 FUNCTIONAL DESIGN ................................................................................................................ 15 


2.3.1 System Attributes and Issues...................................................................................... 16 


2.3.2 Data Flow among Elements of the ANSS.................................................................. 21 


2.3.3 Data Distribution within Processing Centers ............................................................. 22 


2.3.4 Rapid Data Delivery ...................................................................................................... 23 


2.3.5 Offline or Manual Review ............................................................................................. 24 


2.4 REFERENCES ............................................................................................................................ 25 


3 INSTRUMENTATION .................................................................................................................... 27 


3.1 INTRODUCTION .......................................................................................................................... 27 


3.2 APPROACHING THE PROBLEM................................................................................................... 27 


3.2.1 National stations ............................................................................................................ 27 


3.2.2 Regional stations........................................................................................................... 28 


3.2.3 Free field and reference stations (non-structural installations)............................... 28 


3.2.4 Structural arrays ............................................................................................................ 28 


3.3 GENERAL GOALS & EXPECTATIONS ......................................................................................... 28 


3.3.1 Bandwidth....................................................................................................................... 28 


3.3.2 Sensitivity & dynamic range ........................................................................................ 29 


3.3.3 Data latency ................................................................................................................... 29 


3.4 GENERAL DESIGN CONCEPTS .................................................................................................. 29 


3.5 FUNCTIONAL SPECIFICATIONS .................................................................................................. 30 


3.5.1 National station .............................................................................................................. 30 


3.5.2 Regional station............................................................................................................. 34 


3.5.3 Strong motion station (free field and reference) ....................................................... 35 


3.5.4 Strong motion station (structural)................................................................................ 36 


3.6 SYSTEM PACKAGING ................................................................................................................. 36 


3.7 EVALUATION OF COMPETING SYSTEMS.................................................................................... 37 


3.8 DATA FORMAT ........................................................................................................................... 37 


3.9 STATION ARCHITECTURE .......................................................................................................... 37 


4 SITING AND INSTALLATION ..................................................................................................... 39 


4.1 INTRODUCTION .......................................................................................................................... 39 


4.2 SITE CHARACTERIZATION ......................................................................................................... 39 


4.2.1 Obtaining Existing Site Information ............................................................................ 40 


4.2.2 V30 Determination for NEHRP Categorization ......................................................... 41 


4.2.3 Detailed Subsurface Investigations ............................................................................ 41 


4.3 STATION DOCUMENTATION ....................................................................................................... 42 


4.3.1 Basic Station Data......................................................................................................... 42 


4.3.2 Auxiliary Station Information........................................................................................ 42 


4.4 NATIONAL AND REGIONAL STATIONS........................................................................................ 43 


4.4.1 Network Design ............................................................................................................. 43 


4.4.2 Seismic Noise ................................................................................................................ 44 


4.4.3 Site Selection ................................................................................................................. 44 


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ANSS TG v 1.0 

4.4.4 Installation Types .......................................................................................................... 45 


4.4.5 Minimizing Environmental Effects............................................................................... 46 


4.4.6 Installing the Equipment............................................................................................... 47 


4.4.7 Protecting the Station ................................................................................................... 49 


4.4.8 Recommended Installation – National Stations........................................................ 50 


4.4.9 Recommended Installation – Regional Stations....................................................... 51 


4.5 URBAN STATIONS...................................................................................................................... 51 


4.5.1 Important Issues in Station Siting and Design (Non-Structural)............................. 51 


4.5.2 General Siting Criteria .................................................................................................. 52 


4.5.3 Reference Stations on Open Ground (Free Field Stations).................................... 52 


4.5.4 Reference Stations In Small Buildings ....................................................................... 55 


4.5.5 Reference Stations in Densely Urbanized Areas ..................................................... 56 


4.5.6 Structural Response Stations...................................................................................... 58 


4.6 REFERENCES ............................................................................................................................ 62 


5 DATA ARCHIVING AND DISTRIBUTION SUBSYSTEM........................................................ 65 


5.1 INTRODUCTION .......................................................................................................................... 65 


5.2 OPERATIONAL CONCEPT........................................................................................................... 65 


5.3 REQUIREMENTS......................................................................................................................... 66 


5.3.1 System Level Requirements........................................................................................ 66 


5.3.2 Interface Requirements ................................................................................................ 67 


5.3.3 Functional Requirements ............................................................................................. 67 


5.4 OTHER ISSUES .......................................................................................................................... 70 


6 DATA ANALYSIS AND PRODUCTS............................................................................................ 71 


6.1 INTRODUCTION .......................................................................................................................... 71 


6.2 USERS ....................................................................................................................................... 71 


6.2.1 Earthquake Emergency Responder ........................................................................... 71 


6.2.2 Media, Public Officials, K-20 Educators, and the General Public .......................... 71 


6.2.3 Earthquake Engineer .................................................................................................... 72 


6.2.4 Seismic Hazard Analyst ............................................................................................... 72 


6.2.5 Engineering Seismologist and Geotechnical Engineer............................................ 72 


6.2.6 Regional Seismologist .................................................................................................. 73 


6.2.7 Global Seismologist ...................................................................................................... 73 


6.3 RAPID PRODUCTS ..................................................................................................................... 73 


6.4 INFORMATION PRODUCTS ......................................................................................................... 74 


6.5 INTERPRETATION ....................................................................................................................... 75 


6.6 AUTHORITY ................................................................................................................................ 75 


6.7 DATA PROCESSING ................................................................................................................... 76 


7 APPENDICES................................................................................................................................... 78 


APPENDIX A – TIC AND SUBCOMMITTEE MEMBERS.............................................................................. 78 


APPENDIX B – DATA RATE AND VOLUME ESTIMATES............................................................................ 80 


APPENDIX C – INSTRUMENTATION TESTING .......................................................................................... 84 


APPENDIX D − PRODUCTION, INTERPRETATION, AND OUTLETS ........................................................... 85 


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ANSS TG v 1.0 

1 Introduction 

1.1 Overview 

The Advanced National Seismic System (ANSS) is a major national initiative led by the 

US Geological Survey that serves the needs of the earthquake monitoring, engineering, 

and research communities as well as national, state, and local governments, emergency 

response organizations, and the general public. Legislation authorizing the ANSS was 

passed in 2000, and low levels of funding for planning and initial purchases of new 

seismic instrumentation have been appropriated beginning in FY2000. When fully 

operational, the ANSS will be an advanced monitoring system (modern digital 

seismographs and accelerographs, communications networks, data collection and 

processing centers, and well-trained personnel) distributed across the United States that 

operates with high performance standards, gathers critical technical data, and effectively 

provides timely and reliable earthquake products, information, and services to meet the 

Nation’s needs. The ANSS will automatically broadcast timely and authoritative products 

describing the occurrence of earthquakes, earthquake source properties, the distribution 

of ground shaking, and, where feasible, broadcast early warnings and alerts for the onset 

of strong ground shaking. Most importantly, the ANSS will provide earthquake data, 

derived products, and information to the public, emergency responders, officials, 

engineers, educators, researchers, and other ANSS partners rapidly and in forms that are 

useful for their needs. 

The ANSS Technical Integration Committee (TIC) oversees the organization and 

activities needed to develop the technical basis for the ANSS. The strategy for ANSS 

implementation relies on recent advances in seismic instrumentation, wide area computer 

networking, data analysis, and earthquake products, all of which address the needs of a 

variety of users in all parts of the country. The Technical Guidelines for the 

Implementation of the Advanced National Seismic System, Version 1.0 (hereafter, 

Technical Guidelines) augment these advances by establishing guidance that is applicable 

to the national system and by identifying specifications for new equipment and software 

that will better meet the needs of the users of the ANSS. This document describes the 

key design and performance characteristics of the integrated ANSS. 

The implementation of the ANSS will undoubtedly cause significant changes in current 

regional networks. The result will be a new national system, built from standardized 

components, which may include local modifications for special situations. 

The TIC and its subcommittees extracted ANSS design goals from USGS Circular 1188, 

interpreting and expanding them as deemed necessary. The subcommittees then worked 

to develop functional specifications and high-level design elements. The most important 

element discussed has been an overall system organization that forms the framework for 

all subsequent design work. The technical architecture and its development are highly 

dependent on this organizational structure. 

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ANSS TG v 1.0 

The proposed ANSS organization has clear similarities to the current configuration of the 

National Seismic System (NSS). The dependence on local expertise to interpret the data, 

a regional level approach to data acquisition and processing, a national operation center 

to provide a global overview, and a national archiving system all build on concepts of 

proven worth. However, the organization also reflects ANSS goals of coherent national 

integration, highly dependable rapid response, uniform, high-quality earthquake products, 

and widely available data sets. 

As part of the process of developing these consensus guidelines and standards for the 

ANSS, the Technical Integration Committee formed five subcommittees to address 

particular aspects of the system: Archiving and Distribution, Data Analysis and Products, 

Instrumentation, Network Architecture and Interconnection, and Siting and Installation. 

Figure 1 illustrates the responsibilities of the various functional components of the ANSS 

as covered by these committees. 

Figure 1: Functional diagram of ANSS components, color-coded by the 

responsibility of the TIC subcommittees. Primary elements include stations, 

operation centers, archiving facilities, and the links among them. The white boxes 

indicate ANSS users. The ANSS will have both real-time (RT) and archival Data 

Base Management Systems (DBMS). 

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ANSS TG v 1.0 

1.2 Vocabulary 

In describing the design of the ANSS it is important to use a well-defined nomenclature. 

For the purposes of this document the following meanings for commonly used terms are 

followed. Some of these terms have a different emphasis or specific meaning than some 

current uses. 

waveforms – raw, unprocessed, but possibly reformatted ground motion time 

series 

metadata - information needed to process or interpret seismological waveforms 

(station location, instrument calibration, site geology, site velocity structure, etc.) 

products - routinely produced earthquake parameters or other results of automatic 

and manual processing (picks, hypocenters, peak accelerations, shake maps, etc.) 

data - referring to any or all of waveforms, metadata, and products 

information – interpreted seismological data (tectonic framework, hazard 

evaluations, building safety, etc.) 

operation center – A physical facility housing staff and equipment for the routine 

operation and maintenance of ANSS hardware and software and routine data 

processing. Staff includes operators, technicians, analysts, etc. 

ANSS user - anyone interested in acquiring ANSS waveforms, products, or 

information (also referred to as end users or customers) 

Outlet – Any facility that has a standing request for waveforms or products (i. e., 

data and/or products are delivered to the outlet as soon as they are available at the 

respective operation center or archive facility). The many types and 

responsibilities of outlets more fully described in Appendix D. 

data archive system – one or more physical facilities housing staff and equipment 

for the long-term storage and distribution of data. Staff includes operators, 

technicians, and data base specialists. 

(data) client - a software module accessing a shared resource in a distributed 

system. For example, real-time modules within an operation center are clients to 

the shared buffer. Also, a module handling real-time data input at an operation 

center is a client to a remote data source. 

As a system, the ANSS will consist of various functions conducted at one or more 

facilities. The following five main functional activities are at the core of the ANSS. 

Instrumentation: Activities related to the installation, operation, and maintenance 

of field equipment (seismometers, accelerometers, DASes, etc.). 

Concentration: The process of consolidating telemetered, digitized waveforms from 

various station equipment, converting to a common format, and forwarding to one or 

3
ANSS TG v 1.0 

more operation centers. Concentration takes place at data concentrators, which may 

be collocated with other facilities. 

Processing: Activities related to the routine analysis of waveforms to produce 

summary parameters and other products. Routine processing is performed at 

operation centers. Real-time products are pushed to critical users from the 

operation centers. 

Archiving: Functions related to the permanent storage and distribution of ANSS 

data and products and their distribution to end-users. 

Interpretation: Activities related to the generation of scientific, engineering, and 

emergency response information. These include the public and civil authorities 

involved in earthquake response as well as scientists and engineers involved in 

research and development. Interpretation activities also can include feedback for 

the development of new operational capabilities. Interpretation is performed at 

(data or information) outlets. 

Each of the above functions is performed at one or more ANSS facilities and a facility 

may house more than one of these functions. ANSS facilities generally can be classified 

into: 

National: Activities or operations pertaining to the Nation as a whole. 

Regional: Activities or operations pertaining to one of the ANSS regions. 

Information outlet: Activities related to interpreting and providing information to 

end-users. 

Research and Development: Activities pertaining to improvements of ANSS 

processing or information products. 

Contributing: Activities or operations in ANSS partner networks that are not part 

of the ANSS core infrastructure but that exchange data with or augment the 

ANSS in some way (public-private partnerships, State or other Federal agencies, 

foreign entities, etc.). 

1.3 Existing seismic network situation 

Many models of ANSS architecture may be constructed from a combination of functions 

and facilities. Before discussing the ANSS architecture recommended herein, we begin 

with the current system. 

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ANSS TG v 1.0 

Figure 2. Key colors and symbols used for subsequent diagrams of ANSS 

organization. Note that functions (routine operation, interpretation and 

development, etc.) are represented by different symbols while types of ANSS 

facilities are represented by a different fill colors/patterns. 

The current state of national earthquake monitoring is illustrated in Figure 3, where there 

are activities at both the contributing and national level. Symbols in close proximity on 

this figure imply that the functions are collocated at the same facility. At the contributing 

level are the existing regional seismic networks, some supported by the USGS and others 

not. The current activities of these networks (station operation and maintenance, data 

processing, information production and distribution, and archiving) are generally 

characterized by a wide-range of hardware and software solutions and are not uniform 

across all networks. No “regional” (new ANSS meaning of “regional”) activities or 

facilities are illustrated in Figure 3. Although the contributing networks are beginning to 

organize along regional lines, no regional centers have been officially designated. The 

National Earthquake Information Center (NEIC) represents the current level of national 

activities, involving station operations, processing, and information distribution. All of 

the currently contributing centers (RSNs) that receive some USGS funding have 

established data exchange with the NEIC and, in some cases, with other centers. There is 

no true national archiving facility at this time, although some contributing networks 

archive data at the Incorporated Research Institutions for Seismology (IRIS) Data 

Management Center (DMC) while others have established local archives. 

5
ANSS TG v 1.0 

Figure 3: In the current system, the local processing centers are characterized by a 

wide range of hardware and software. Functionality of the system elements is 

highly variable though each center usually houses all functions mixed together. Data 

exchange between centers is highly variable. 

Although many aspects of the seismic monitoring in the United States have improved in 

the last few years, the current operations do not represent a true "system". In fact, the 

majority of seismic monitoring stations in the US are still short period stations, and 

strong motion sensors often are not digitally recorded. Although some components 

perform extremely well, others do not. Overall, the current state of seismic monitoring 

lacks a coherent and integrated structure. This is one of the major problems that the 

ANSS addresses. 

The current state of seismic monitoring is characterized by a complex topology, which is 

highly heterogeneous (different hardware and software in the different components) as 

well as highly asymmetric (different levels in the system performing different functions). 

Most current networks perform all functions at the same place with the same personnel. 

Products are ad hoc and not universally available and no uniform standards are applied. 

The existing system also has some fundamental vulnerability due to several operating 

facilities being located in areas of high seismic hazard. 

1.4 Basics of the ANSS organization 

It is clear from Circular 1188 (a basis for the authorizing legislation for the ANSS) that a 

change from the current organizational structure is needed. Based on a review of circular 

1188 and related documents, reports of the TIC subcommittees, and review and 

discussion within the TIC, we recommend an organizational structure with a strong and 

relatively standardized regional and national structure for routine monitoring operations 

and a separation of the development and interpretation functions from routine processing. 

This model is based on the following assumptions and characteristics: 

1. The ANSS is a complex system. A system is "hardware, software, and people 

working together to solve a particular problem, or to produce a desired effect." 

All components of the system need to be considered in order to produce the 

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ANSS TG v 1.0 

ANSS. A "systems engineering" approach will be applied to the detailed design 

of the ANSS. 

2. To maximize reliability and produce uniformly high quality waveforms and 

products the operation of the ANSS will be undertaken by a dedicated operations 

staff. At the same time, to make ANSS products relevant and effective, ANSS 

design and management should be undertaken by scientists and engineers. 

3. Close coordination between the routine operation functions and the 

design/interpretation functions is essential. 

4. The ANSS is organized into regions, a national operation center, and a national 

archiving system, with one primary and perhaps other secondary operation 

facilities within each region. The regional operation centers will be responsible 

for managing the instrumentation and data collection within the region and for 

routine processing, and reporting on earthquakes in their geographical area. Each 

state or territory falls within a region. 

5. The ANSS must provide mechanisms for distribution of earthquake information 

and products to a wide variety of users over a broad range of time scales. The 

operation centers have the responsibility to provide earthquake waveforms and 

products to time-critical users, while the archiving facilities distribute waveforms 

and products to non-time-critical users. 

6. The ANSS will have a single long-term archiving system that is decoupled from 

the real-time routine processing functions. This may be a distributed system or it 

may be a single archive facility. Proper care must be taken for the ultimate 

recovery of all archived data in case of facility failure, and recent data must be 

recovered quickly. Ultimately the archiving system must insure that the system 

functions through periods of natural disasters and insure the long-term 

safekeeping of all data and derived products for future use. 

7. The requirements for the ANSS will evolve as the system develops and even after 

it is fully deployed. Mechanisms to allow changes and evolution in the technical 

and functional specifications and design as development efforts are evaluated will 

be established. 

The ANSS requires multiple routine operational centers to avoid single points of failure 

and to be able to adapt quickly and efficiently to special regional conditions or situations. 

Therefore the ANSS requires robust and reliable exchange of a variety of data and 

products among facilities or components of the system. There is little difference between 

the national and various regional operating centers other than size and geographic areas 

of responsibility. In general there will be only one primary operational center per ANSS 

region at which routine data processing for the whole region will be done. The national 

level operation center will act as backup for all regions as well as coordinate issues 

between regions. One or more of the regional centers (or a separate facility) will also act 

as backup for the national center responsibilities in the event of a failure at the national 

center. 

A fundamental difference between the ANSS and the current monitoring situation is a 

clear separation of the routine operation of the ANSS from the development and 

interpretation aspects, as discussed in Appendix D. While in some of the currently 

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ANSS TG v 1.0 

operating network centers there is some separation of these responsibilities there is rarely 

a formal distinction. The interpretation and development personnel are involved with 

operations from time to time at nearly all existing networks. The capabilities of modern 

computer networking obviate the requirement that they be housed in the same physical 

facility though in some cases there may be reasons to do so. Figure 4 illustrates the ANSS 

organizational structure: the functions of routine operation are separate from 

interpretation and development. A contributing (currently operating) network closely 

involved with a regional ANSS operation is included. Connecting arrows represent data 

or information flow paths. Line thickness is proportional to data volume. 

Figure 4: This figure illustrates the ANSS organizational model, consisting of 

regional and the national centers with associated interpretation functions 

distributed more widely. A contributing network is shown with open symbols but is 

not an official part of the ANSS. 

Generally the flow of data through the proposed model for the ANSS is from bottom to 

top. At the bottom, seismic stations measure ground motion that is telemetered to data 

concentrators collocated with operation (data processing) centers. Data concentrators may 

be installed at remote locations to concentrate data from several seismic stations, perhaps 

reformat the data into standard ANSS data packets, and forward these data to operation 

centers over high capacity data communication circuits. National backbone stations are 

telemetered directly to the national operation center on independent circuits. Note that 

data telemetered into a data concentrator are immediately passed on to other centers as 

well as the local center. Automated earthquake products are produced at the operation 

centers and immediately distributed to interpretation outlets. Automated products are 

coordinated system wide through a set of business rules. 

The critical task of interpretation of ANSS data is conducted at information outlets. 

While the real-time ANSS infrastructure has been simplified in the interest of reliability, 

information outlets encompass everyone involved in translating seismic waveforms and 

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ANSS TG v 1.0 

products into earthquake information. Note that information outlets have access to as 

many waveforms and products as needed to perform their function. 

The modularization of data acquisition, processing, and consumption (at the outlets) 

provides considerable flexibility in the ANSS infrastructure. For example, data 

concentrators could be remote from any operation center, concentrating stations onto 

high-speed communications links, and providing the data to multiple operation centers. 

Alternatively, station data could be multicast from the field to several operation centers 

and an archive facility through collocated data concentrators. The ability to collocate a 

concentrator with an operation center means that the design of the operation centers or 

archive facilities is independent of the field telemetry architecture. 

The concept of an outlet is very general and many types are envisioned. Outlets involved 

in rapid response activities (state offices of emergency services (OESs), emergency 

manager's trusted sources, and institutions interpreting the data for the media) are fed 

data and products directly from operation centers. Non-time critical outlets (e. g., 

research and development) are fed data from the data archive facilities to ensure complete 

data sets and to prevent burst loads on critical real time facilities. Outlets fed from the 

archive facilities may still be performing mission critical ANSS tasks (catalog 

production, hazard studies) and may still receive data in real time. Outlets may be 

operational (involved in reviewing real-time products) or informational. Outlets may be 

involved in the development of new ANSS products, procedures, or algorithms. 

Each operation center serves as a production outlet, interacting with the data archive to 

provide authoritative reviewed products, maintain metadata, and perform quality control 

(QC) functions. Quality control encompasses activities that assure the user of the quality 

of distributed data and products and may include manual product review, station 

calibration, metadata validation, and monitoring of field clock quality. Reviewed 

products (including quality controlled waveform data) are transmitted to the data archive 

facility as soon as they are completed. The one-to-one association between these special 

production outlets (shown in the same color as their respective operation centers in figure 

4) is necessary to ensure that reviewed products have the same authoritative status as 

automatic products. Note that it is not essential that all operational functions be 

conducted in one production outlet per operation center. For example, it might be useful 

to collocate the rapid review of products with the operation center to enhance reliability 

while metadata maintenance functions are done elsewhere. For a more complete 

description of outlets, see Appendix D. 

The ANSS must establish appropriate standards for operation. Detailed standards are 

beyond the scope of this document. However, they should be established early in the 

development of the technical components of the system and be based on sound practice 

and technical capabilities. These standards for operation should be reviewed and updated 

as appropriate at a national level. 

The ANSS is a revolutionary effort to modernize the seismic monitoring system within 

the United States. The design of the ANSS should not be hampered by the state of 

seismic monitoring prior to the start of ANSS. Nevertheless, it is important to define an 

evolutionary path from the current situation to the final model, without interrupting 

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ANSS TG v 1.0 

operations. Implementation of this transition will be the responsibility of the ANSS 

Implementation Committee assisted by the regional working groups; however the TIC 

assumes that most current network operations will become involved in some aspect of the 

ANSS organization. Some of the existing network operations centers may become 

regional operation centers. Others will take on the important tasks of interpreting ANSS 

data and helping with development of new ANSS capabilities. 

Detailed aspects of the ANSS system design and functional specifications for its various 

components are covered in the following chapters. Each is largely based on the 

respective subcommittee reports. In particular the “Network Architecture and 

Interconnection” chapter is critical to the system as a whole. 

1.5 Evolution of the Technical Guidelines 

The Technical Guidelines is the first step in the implementation of the ANSS. It outlines 

the basic architecture of the ANSS and provides general guidelines on key technical 

issues regarding data collection, archiving, and analysis; instrumentation; site installation; 

and dissemination of products. Detailed technical standards are beyond the scope of this 

document, but will be developed based on these guidelines, sound seismological practice, 

and technical capabilities as technical components are developed throughout the 

implementation of the ANSS. 

This document represents the collective wisdom of a large portion of the seismological 

and earthquake engineering communities, summarized in technical reports from five 

subcommittees that form the basis of this document. The ANSS Technical Integration 

Committee (TIC) edited, reorganized, and repackaged the subcommittee reports, adding 

text as necessary. The Technical Integration Guidelines is very much influenced by the 

state-of-the-art today, and yet attempts to be visionary. This document is intended to be a 

living document that forms the technical framework for the ANSS. The TIC understands 

that as the system develops, technical questions relating to the development, deployment 

and operation of such a large system will require additional input. The Technical 

Integration Guidelines will continue to evolve and adapt to changing requirements as 

necessary. Revisions of the Technical Integration Guidelines document (exclusive of 

attachments) will be published as higher version numbers (e.g., a minor revision to 

accommodate the first attachment might be version 1.1, while a major revision of one or 

more chapters might be published as version 2.0). 

The TIC anticipates that input of a technical nature will continue to be needed by the 

ANSS. For this reason we recommend that the TIC continue to exist throughout the life 

of the ANSS to provide technical input and direction to the National Implementation 

Committee. We further recommend that the six members of the TIC continue to serve 

terms such that two members rotate off the TIC on an annual basis and two new members 

rotate on to the TIC. From time to time the TIC may populate a variety of temporary 

subcommittees or working groups where specific expertise is needed. In this manner the 

ANSS can continue to respond to new technological challenges as they arise. 

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ANSS TG v 1.0 

2 Network Architecture and Interconnection 

2.1 Overall Organization 

The TIC recommends a regionalized architecture for the ANSS with a primary 

operation/processing center in each ANSS region and a single national 

operation/processing center. This model provides multiple processing centers for 

redundancy, while allowing for customization for regional needs. This model also 

provides a natural scale for addressing issues of data quality control, scalability of 

processing systems, redundant reporting, product quality control, and flexibility and 

responsiveness to local contacts. Besides the primary operation/processing center for 

each region, there may be multiple operation centers for station and telemetry 

maintenance and multiple information outlets. Existing local networks likely will be 

transformed into an operation center or information outlet. The regional model of the 

ANSS implies consolidation and coordination of effort among the participating networks. 

The facilities of some local networks may become maintenance and data concentrators 

with processing activities occurring at the regional center. Local network operators may 

continue to be involved in station operation and maintenance, but their scientific 

expertise also will be devoted more to interpretation, research, and development using 

data from any subset (or all) of the ANSS. 

The rest of this chapter concentrates on the initial design of the routine operation part of 

the ANSS. While scientists and design engineers will be involved with development 

work on these components, professional engineers, programmers, and operators will 

perform the actual implementation and operation. 

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ANSS TG v 1.0 

Region 

Region Region 

National A 

B C 

Figure 5: A map view of the hierarchy illustrated in Figure 4. This figure shows 4 

adjoining regions with various ANSS elements. Note that existing networks are 

shown as collocated data concentrators and outlets. Regional and national centers 

are shown with the associated outlet collocated (collocated concentrators are not 

shown). Also, a distributed archive is hypothesized with both national and regional 

elements. 

The ANSS is a complex system, partly due to the number of nodes and interconnections. 

Therefore the TIC recommends minimizing the number of regional centers and 

concentrators within individual regions. The model calls for establishing one processing 

center per region, but recognizes that there may be exceptions. The advantages of 

locating the regional processing centers away from areas of significant seismicity are 

obvious. At a minimum, ANSS centers must be placed in facilities where appropriate 

earthquake resistant mitigation efforts have been completed. Note that local expertise will 

be available at many of the data outlets 

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ANSS TG v 1.0 

In this model, the regional processing center will be the central hub of routine operations 

in an ANSS region. This center will have primary responsibility for rapid earthquake 

processing and notification. While the regional processing center will receive waveform 

and parametric data from different components of the system, and from adjoining 

regions, it will be the authoritative source of information on earthquakes in its region and 

will have responsibility for distribution of this information in near-real time to a 

multitude of information outlets. This role in the processing and distribution of rapid 

earthquake information makes the regional processing centers critical elements of the 

ANSS, requiring high levels of performance and robust and reliable operation. The 

national processing center will have similar capabilities and will receive data from all 

regions and the national stations and be capable of acting as backup for all regional 

processing functions. The national processing center will also act as coordinator between 

regions and arbitrate between discrepancies in products provided by different regions for 

the same event. The success of this regionalized model depends on the requirement that 

operators adhere to ANSS performance standards. 

2.2 General Issues and Recommendations 

Quality control for the ANSS is crucial and must be a fundamental part of the ANSS 

system. Due to the number of seismic stations, number of channels, volume of waveform 

data, and abundance of products, quality control will most likely have to be much more 

automated than in the past. Systems must be designed to routinely monitor the 

characteristics of waveforms, including time, and data quality (dropouts, noise, etc) and 

alerts must be generated when parameters fall outside acceptable limits. Part of the 

system specification will clearly identify the performance standards. 

Major types of quality control must address items such as 1) waveform timing, 2) quality 

of instrument calibration including schedules for calibration, 3) accuracy of station 

metadata, 4) data availability statistics (uptime), 5) error estimates of measured 

parameters such as phase picks, and 6) error estimates of calculated parameters such as 

hypocentral locations or moment magnitudes. System wide quality control techniques 

(for example, using mining blasts to check station timing) will be important. Metadata 

will be maintained at the regional centers and techniques to test the accuracy of the 

metadata will be necessary. 

Quality control is an ANSS-wide issue. The methods and techniques used to monitor data 

quality should be standard. Although individual regions may have specific problems, the 

development of quality control techniques and standards should be consistent across the 

entire system. 

Distributed reporting of rapid earthquake information raises questions about robust data 

delivery if a regional processing center is disabled. Although the ANSS could implement 

a “nearest-neighbor” regional backup model, having the national processing center act as 

the backup to each region is the simplest model. At least one regional processing center 

(or a separate facility) must be able to reproduce the capabilities of the national 

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ANSS TG v 1.0 

processing center in terms of global monitoring in the event of a failure at the national 

processing center. 

Rapid notification requires rapid review in order to confirm event validity or to remove 

spurious events. It is anticipated that each production outlet involved in rapid review will 

require a staff member to be either on site or on call at all times – with the expectation 

that earthquake alarms will be reviewed within a few minutes after notification. 

The generation of reviewed earthquake products will be performed in each region. 

Strictly speaking, the system architecture is relatively insensitive to the location of this 

activity. Although some aspects of design are simplified if this is centralized at a national 

facility, it seems clear that each region can provide more local understanding and should 

be responsible for its earthquake products. Production outlet(s) closely associated with 

the national processing center will be responsible for coordinating regional products, 

producing uniform national products, and producing and reviewing products for global 

events. Appropriate business rules and mechanisms will be required to keep the national 

and regional products synchronized. 

The ANSS will be a real-time system with all stations connected to real-time telemetry 

links (including structure-monitoring arrays). While some channels may be telemetered 

only when triggered by strong shaking, the system must be capable of telemetering all 

channels in real-time, with possible minor delays (seconds) in extreme cases. 

We assume that there will be no fundamental difference between the way weak and 

strong motion data are handled. Network design goals for real-time strong-motion 

stations are, in principle, the same as for other seismic instrumentation. However, some 

data will not arrive in real time, either because of telemetry failure or network congestion, 

particularly during large events. Thus the ANSS must be designed to handle late data as 

well as data that arrive out of order. 

The size of the data channels, both within processing systems and for telemetry between 

centers, is well within the technical limits of computer and networking technology, 

particularly since this technology continues to advance at a rapid rate. The aggregate 

data rate of all ANSS seismic channels is assumed to be less than 20Mb/s (see Appendix 

B). Including data from non-ANSS sources will increase this rate but it should still be 

within technical limitations of even current capabilities. 

Standardization, particularly as it relates to software, is a tricky issue. Using the exact 

same software is desirable to maximize efficiency and provide uniform products. 

However, uniformity often stifles innovation and in any case the system must be designed 

so that it has flexibility to deal with special local or regional problems. The TIC proposes 

that software for routine operations be largely standardized, but allow for local 

customization where warranted. The TIC sees no reason to require standardization at 

outlets other than the production outlets. Rather, software diversity at most outlets 

should be encouraged to promote the development and testing of new operational as well 

as interpretation algorithms. 

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2.3 Functional Design 

To address the issues of functional design for the ANSS, this section is organized into 

several subsections: 

• System Attributes and Issues 

• Data Flow among Elements of the ANSS 

• Data Distribution within Processing Centers 

• Rapid Data Delivery 

• Offline or Manual Review 

Figure 6: Schematic illustration of ANSS functions and data flow among ANSS 

elements. The large rectangles encompass the tasks of regional/national processing 

centers and production outlets. 

To facilitate the discussion of these issues, Figure 6 illustrates the ANSS design in greater 

detail. This figure uses the symbology of Figure 2, but does not attempt to identify 

different levels of functionality. For example, the processing operations (square) include 

components for data acquisition, "online" or automated processing, "offline" or manual 

review processing, and quality control (encompassing data concentrator, processing 

center, and production outlets). There are also elements for rapid notification, archiving, 

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ANSS TG v 1.0 

and data distribution. Colored lines among elements of Figure 6 indicate communication 

links where waveforms, metadata and products may flow. Some of these transactions 

will be continuous (for example, waveform exchange among the processing centers and 

to the archiving facilities) while others will be on-demand (for example, possible use of 

database interactions). 

Figure 6 also illustrates the different levels of data persistence or storage that may be 

required by the ANSS. Processing systems will use two levels of data buffers. One 

provides for relatively recent data and will be designed so that real-time processing 

applications associated with the processing center can access data in the appropriate time 

frame. The second level of data buffer is provided for intermediate-term storage 

associated with production outlets for rapid review and other QC purposes. The 

distinction in terms of the timeliness of data access is important, depending on the type of 

request. 

2.3.1 System Attributes and Issues 

2.3.1.1 Evolution 

From telecommunications to computational capabilities to networking to storage 

capacity, the technological underpinnings of the ANSS will change dramatically over its 

life span. It is essential that the ANSS be developed so that it can grow and evolve over 

time, both to take advantage of these changes as well as to respond to changes in the 

needs of the user community. In order to evolve, it is critical that the ANSS system be 

based on an open and extensible architecture, widely adopted standards, modern software 

concepts, and platform independence. 

2.3.1.2 Standard Networking Tools 

The ANSS should use standard networking techniques including TCP/IP, domain name 

servers, and route determination using commercial standard routing protocols. The 

ANSS development should NOT take on the design of alternate networking techniques. 

2.3.1.3 Standardized Interfaces, Protocols, and Formats 

All data flow, whether within or between elements of the ANSS, should use the same 

interfaces, protocols, and formats. All data access functionality must be provided to data 

client processes via a standard, well documented Application Programming Interface 

(API). This approach will reduce costs, and increase flexibility, scalability, and 

maintainability. For the purpose of system architecture, ANSS data falls into several 

distinct classes: 

• waveforms (with triggered waveforms as a special case) 

• parameters (such as picks, hypocenters, moment tensors, station metadata) 

• binary, large objects (a.k.a. BLOBs, such as ShakeMaps). 

The ANSS must be able to handle these three fundamental classes through the 

establishment of standardized interfaces for data exchange. In addition to supporting 

these three data classes, the ANSS will support the two following types of requests: 

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ANSS TG v 1.0 

• Standing order (continuous and on-going feed) 

• Discrete request (one-time request for a specific set of data) 

. 

An example of the standing order request might be the exchange of continuous waveform 

data between processing centers. The exchange of associated station metadata could also 

be considered a standing order, but of the parametric class. In contrast, a request for a 

particular waveform time segment, say, to fill in a data gap, would be an example of a 

discrete request of the waveform class. 

In designing the APIs, the ANSS must bear in mind the following four different classes 

of clients: 

• Elements within the routine operation of ANSS 

• ANSS interpretation and development outlets 

• Non-ANSS networks 

• Users of ANSS products 

2.3.1.4 Modularity 

The ANSS software and hardware components should be highly modular. That is, each 

function in a system should be encapsulated in a separate module and each module 

should operate independently. While this design principle may not be possible to adhere 

to in all cases, it has a number of advantages. In particular, it allows new functionality to 

be added without compromising existing capabilities. 

2.3.1.5 Scalability 

The ANSS must be scalable. The current proposals for the ANSS call for approximately 

ten thousand monitoring sites. However, given recent advances in microelectronics, this 

number could increase by more than an order of magnitude if inexpensive, small sensors 

are distributed widely and used to monitor buildings, bridges, and lifeline networks. Such 

a capacity may be achieved by dividing processing tasks among many instances of the 

same processing module, each running on a different processor and each handling a 

subset of the total data set. This modular "divide and conquer" approach, if correctly 

designed, can provide relatively open-ended scalability. Note that in order to achieve 

scalability by adding hardware, the software architecture must be designed for distributed 

processing from the ground up. The ANSS must leverage modern approaches to software 

design and development to insure scalability. 

2.3.1.6 Complexity 

It is important to recognize that functionality (number of fancy features in the system) 

and performance tend to be inversely related. Therefore, critical subsystems (e.g., 

communication substrate and buffers) should avoid extra complications or processing 

“features”. Wherever possible, the capabilities of existing communications protocols and 

widely available operating systems features should be used. For example, this could 

mean relying on the checksums and packet-dropout detection of TCP/IP or on operating 

system features such as threading for multitasking or by leveraging multicast technology 

if appropriate. 

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2.3.1.7 Data volume 

An important issue for the design of the ANSS is sizing of communications links and 

processing systems. While adjoining regional processing centers may implement partial 

waveform exchange, the national processing center and the archiving facilities will see 

the full data flow in real time. At a minimum, each element of the system should be sized 

to allow for complete data recovery and processing for the largest earthquakes in normal 

operation and to quickly recover from partial telemetry outages. This will require 

telemetry and processing capacity to exceed the nominal data throughput. Note that a 

single M = 8 earthquake in Central California will involve collecting and processing a 

significant fraction of available ANSS waveform channels. 

Appendix B provides estimates of the data volume that the TIC believes to be relevant for 

system design. In general, continuous streams of data from all instruments must flow 

from stations to processing centers. Network triggering will significantly reduce the data 

volume from the strong motion instrumentation, but data from broadband seismometer 

channels will be continuous all the way to the permanent archive. 

2.3.1.8 Buffering 

The system must be capable of buffering all available ANSS waveform and parametric 

data to ensure both complete processing when capacity is degraded and complete and 

error free transmission throughout the system (from field stations to end users) when 

communications links fail. While it is not practical to plan for all contingencies, at least 

one week of data should be buffered at all data concentrators, processing centers, and 

production data outlets. Buffering recommendations for field stations are discussed in 

chapter 3. 

2.3.1.9 Speed 

The requirements of early warning, calculation of real-time location and magnitude, and 

real-time data distribution dictate that data delivery and processing delay (latency) are 

minimized. The system should add no systematic delays to the latency inherent in 

delivery from the data source. Since a data packet cannot be resent until it is fully 

received, store-and-forward type of data delivery relays should be minimized and data 

packet lengths for high digitization rates should be no more than a few seconds of data. 

Additionally, the latency associated with data buffers, the number of "hops" in the data 

paths, and steps in data processing must be reduced as much as possible. 

Late data - whether from triggered data streams or from communication outages - will be 

a fact of life. The ANSS must be designed to process late data. Late data should be 

organized seamlessly with data already received and late data should be incorporated in 

ANSS data products to the greatest extent possible as they become available. Also note 

that some products of the ANSS (e.g., waveform data for seismological research) require 

high levels of data completeness. At a minimum, the tradeoff between latency and 

completeness will require that older data must be transmitted out of order after a 

communications outage to minimize the latency of current data. 

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2.3.1.10 Security 

The ANSS must be a secure system. The design must ensure that critical computers are 

secure against intrusion, denial of service attack, and “hacking”. Authentication should 

be used to allow data service only to authorized clients. Rapid notifications should also 

be protected against "spoofing". The TIC does not feel that data authentication, as used 

by the CTBTO, is necessary. 

2.3.1.11 Reliability 

The simplest statement of the ultimate reliability specification of the ANSS is that a total 

system failure during any significant event is unacceptable. In practical terms this means 

that enough of the ANSS must be operational at all times to provide reasonably high 

quality information about any potentially damaging event in the U.S. throughout the life 

of the system. On the other hand, it is expected that the full performance of the system in 

terms of response time and accuracy should be available a very high percentage of the 

time. This is inevitably a cost-performance issue. 100% availability is, in practice, 

impossible to guarantee and the cost of closely approaching this ideal grows 

exponentially. This is the best single argument for multiple, geographically isolated, data 

processing centers with national backup. 

2.3.1.12 Robustness 

While multiple data processing centers, data outlets, and archive facilities greatly 

enhance system reliability, they also significantly increase the probability that parts of the 

system will be unavailable at any particular moment. Therefore, the ANSS must perform 

as well as possible under all likely partial failure scenarios. For example, it would be 

unacceptable to delay notification because all data were processed with inadequate 

capacity. Similarly, dropping 1 second of data every 20 seconds because of inadequate 

communications bandwidth would make all the data useless. One mechanism that has 

been found to enhance the performance of systems under stress is to prioritize the data so 

that all data delivered are usable and processing is still effective and timely, even though 

the data set processed in real-time may be incomplete. 

2.3.1.13 Communication Links 

Mission-critical communications, at all levels, should be over a variety of independent 

physical paths to increase reliability. Path diversity is already built into some telemetry 

systems, especially commercially supported ones. For example, Internet routing is 

dynamic and "self healing". However, no single medium is 100% reliable and the ANSS 

should not have "all of its eggs in a single communications basket," be it a physical link 

or technology type. Multiple links must be considered for major paths such as between 

processing centers and to the archive facilities. Designs for using multiple paths include 

switching from one route to another quickly and automatically if a fault is detected, 

splitting communications among different paths so that a failure only affects part of the 

data flow, and dynamic shifting of the load when links degrade. 

Necessary attributes of the data exchange protocols are that they be robust and reliable. 

Possible implementation considerations are the ability to prioritize data to allow for 

graceful degradation, using heartbeats and handshaking to insure completeness, error 

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detection to avoid corrupted packets, and filtering to allow selection of particular data 

products. 

2.3.1.14 Health and Status Monitoring 

The ability to measure the health and status of the ANSS will be a critical aspect of the 

design. The operators of the ANSS need the ability to easily identify problems or failures 

in the system, ranging from loss of data due to communication problems, to the failure of 

processing computers or equipment. The implementation of system monitoring 

components will include elements such as the assessment of sensor health, connectivity 

to sensors, communication between and among centers, data latencies, status of 

processing elements, status of computers, routers, and other hardware, and ability to 

perform data distribution. 

2.3.1.15 System Testing 

In addition to monitoring individual elements, it is necessary to provide “total” 

assessments of ANSS functionality. This should include both off-line simulations of 

typical and worse case conditions (for example a large earthquake during a partial 

telemetry loss) and on-line injection of test events/signals (without loss of real data) for 

testing the system as a whole. Similarly, new algorithms and configurations should be 

well tested before they provide information to ANSS users. 

2.3.1.16 Ease of Operation 

Experience operating large seismic networks shows that substantial time and effort are 

required for reliable operation. The ANSS development should have significant effort 

devoted to making the system easy to operate. Issues that should be addressed include 

configuration, initialization, upgrading software, and reconfiguration of the system. 

Alternate systems for operational procedure training should be provided. Complete and 

well-organized documentation must be kept accurate and current. 

Configuration - Network and monitoring configurations must be easy to establish 

and check. Configuration information includes things such as station metadata, 

telemetry connections, hostnames, and other information. Configuration 

information must be part of the basic ANSS database system (i.e., configuration 

parameters must be available through the same mechanisms as other parameters). 

Configuration information entered into the system must be propagated 

automatically to all modules needing it. It would be desirable for “smart” field 

instrumentation to propagate information about changes in the field as they occur. 

Initialization of System - The system, or any part of it, must self-initialize when 

started and provide positive information that it restarted properly and is 

operational. The injection of test data, possibly waveforms, into the system on 

initialization might be used for system verification. 

Reconfiguration of System. - The ANSS system must be reconfigurable while it 

operates. It should not normally need to be restarted to re-read configuration 

information but rather reconfigure dynamically without exiting or loss of data. 

Reconfiguration must support versioning or journaling such that if a new 

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configuration is discovered to have problems it should be easy to revert to an 

earlier configuration. 

Alternate computers for maintenance and development. – Backup hardware for 

critical parts of the system must be available for redundancy and would be used 

for both emergency backup and routine maintenance of primary systems. 

Diagnostic Tools. - The ANSS should provide the ability to monitor system load 

and diagnose software and hardware problems while the system is in operation. 

Tools for both hardware health and software conditions should be routinely 

available and used by system operators. Commercial monitoring techniques and 

protocols such as SNMP should be used where appropriate. Software tools should 

allow operators to view results anywhere in the processing. 

Operational Procedures. - The ANSS should establish systematic operational 

procedures to insure the health and maintenance of the system. Operators should 

make routine checks of various aspects of system operation but also be well 

enough trained to recognize problems or conditions which fall outside those 

detected by the routine checks. 

Documentation. - The ANSS must provide simple, straightforward operational 

procedures documents as well as more detailed technical documents for both 

problem solving and development purposes. Documents must be completed and 

reviewed before any referenced process or procedure becomes operational. 

Patches or changes to software or procedures must be fully documented as they 

are made. Significant clerical effort should be part of the development and 

operational process to insure that both relatively static and dynamic 

documentation is well maintained. 

Knowledge Base and Discussion Forum. - To assist with operation and 

development the ANSS should provide three things: (1) a knowledge base so that 

users can find information about the system on their own, (2) training classes so 

that operators and users of the system can be educated in the system, and (3) a 

discussion and problem-solving forum for the dynamic solution to problems and 

development of new techniques. Suitable forums include face-to-face meetings, 

telephone conferencing, e-mail distribution lists and WEB based notes of the 

discussions. 

2.3.2 Data Flow among Elements of the ANSS 

2.3.2.1 Data Concentrator 

The data concentrator is the heart of the telemetry system. The concentrator will receive 

waveforms from stations, check for validity, and pass them on to one or more processing 

or archiving centers. The data concentrator may convert waveform packets into a 

standard format. This node could be a small, remote facility where multiple field stations 

are consolidated onto high bandwidth telemetry links or it could acquire data for a 

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collocated processing or archiving system. Concentration nodes will require significant 

data buffering to ensure complete data across communications outages. 

2.3.2.2 Data Tracking 

The ANSS must be able to track the lineage or provenance of its data. Given the 

potential for distributed data acquisition and exchange among multiple components, 

tracking data as it flows through the system is a requirement. In addition to documenting 

the path, the tracking tag also assures the non-ANSS data provider of appropriate 

attribution. Although the complete solution is beyond the scope of this document, data 

tracking should at least include identification of the initial source of the data as well as 

the ability to indicate any processing or modification of the data and the agency that 

performed those operations. 

2.3.2.3 Distributed databases 

It will be necessary to synchronize the data holdings of processing centers and production 

outlets with archiving facilities. This concept is discussed in Chapter 5. 

2.3.3 Data Distribution within Processing Centers 

The requirements for data flow within an ANSS processing center are very similar to 

those for communication among centers and from centers to outlets. However, there are 

some special considerations to be addressed for data delivery within a center. These 

requirements are controlled by the processing function or functions with the most 

extreme demands for data volume, data delivery speed, and buffering (data persistence). 

2.3.3.1 Buffering 

The heart of the processing center will be the mechanism to buffer data received from the 

concentrators for use by all interested clients. The system must buffer the data long 

enough for client applications to have a reasonable chance of successfully getting all the 

data they need to do their work. This data buffering may be shared with a collocated 

concentrator. Data buffering also allows out-of-order data to be sorted before use. A 

common buffer within the data transport system avoids duplication of the data into many 

application-specific buffers. 

2.3.3.2 Other requirements 

Security and client management - The processing system as a whole must manage clients 

to assure predictable behavior and guarantee service to mission critical clients. 

Authentication will be used to allow data service only to authorized clients. 

System management - Tools will be provided to report and monitor the performance and 

load of the system. 

System topology - The system topology must be flexible. It must be able to distribute 

modular functions over multiple hosts and they should be free to move from host to host. 

Single-points-of-failure will be reduced to an absolute minimum within any one center. 

All critical functions will be offered by redundant servers. Switching from one server to 

an alternate will be simple, fast and, where possible, automatic. The system will be able 

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to handle additional data volume by adding modules or hosts. Dynamic load balancing 

would enhance the reliability of the system. 

Stable load - Where possible, the behavior and resource consumption of the system will 

be steady and predictable. 

Exception handling - Exception handling must be part of the ANSS software. The 

software must fix or report corrupted, out-of-order, or incomplete data. It must allow 

clients to specify and handle time-outs for data requests. 

2.3.3.3 Data Clients 

Data clients include components of the data distribution system, real-time processing 

modules, post-processing modules, quality control modules, and updates and information 

transfer to the archive. Data clients have a need to make standing orders or discrete 

requests (from either the fast or slow buffer). However, client connections must be 

stateless (each new connection must negotiate the data stream). 

The number of client modules in an operating center may be large. Data transport 

architecture between the common buffer and client processes must provide adequate 

throughput, low latency, and reliable delivery. 

2.3.4 Rapid Data Delivery 

Rapid earthquake notifications will be one of the most important responsibilities of the 

ANSS and a key to the usefulness of many products. Rapid data and product distribution 

is distinguished from distribution from the archiving system primarily because of the 

time-critical need for the data. The system should be capable of rapidly generating many 

types of earthquake products, and each type must be automatically delivered in standard 

formats via multiple mechanisms. 

2.3.4.1 Early Warning 

The ANSS earthquake processing system must provide information on a number of time 

scales but the fastest is essentially in real-time: information must go out to end users 

before the shaking from a large earthquake is over (possibly before shaking starts at some 

places (early warning)). While such speeds may not be attainable early in the system 

development, the goal for the ANSS must be to support continuous improvements in 

speed of production over the life of the system. The ANSS will be designed so that the 

system distributes earthquake information as quickly as it is determined. The system 

must allow for improvements in processing capability that accelerate rapid notifications. 

When the notifications are fast enough, early warning will be available. 

2.3.4.2 Improvement with Time 

A fundamental principle of earthquake data processing is that information about an 

earthquake improves with time. As time passes, the acquisition system acquires more 

data and the processing system has more time to process the data. Given more time, 

more sophisticated algorithms can be used and with enough time, human interaction with 

the data is possible, allowing greater improvements in accuracy and completeness. 

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All data and products must be uniquely labeled and versioned to distinguish between new 

items and updates. A time-stamp and the identity of human reviewers should be included 

as well. When products are updated the latest update should take precedence over any 

earlier products of the same type for the same event. However the system must retain 

access to previous published versions of the products. 

2.3.4.3 Precision and Accuracy 

Data and products distributed by the ANSS must include an associated assessment of 

their accuracy and the precision with which they are produced. Methods for determining 

the accuracy of the data and products must be agreed upon and used nationally. The 

assessment of quality will naturally vary by data type. Quality tags are needed to provide 

product recipients with a measure of how the information should or should not be used. 

When products improve with time, quality measures become particularly important. 

These measures may also be used as flags for some users who are interested in only the 

highest quality information. 

2.3.4.4 Best Answer 

The ANSS will provide a single published description for any earthquake in the U.S. 

With multiple processing centers producing earthquake information, implementing the 

“one authoritative answer” approach will be challenging (particularly since some region 

boundaries cross seismic zones). The technique of providing the one and best solution 

for public use must be based on clear and programmable ‘business rules’. Such rules will 

be based primarily on speed and quality (i.e. the fastest best result becomes the public 

one). As new or different solutions for a particular event become available within the 

system there must be a clear way to rapidly determine if they should supercede the 

current public version or not. Manual over-ride of the automatic system must be 

available, including the ability to cancel a spurious event out right. 

2.3.4.5 User Formats 

Some end users will require messages in specific formats or delivered by special channels 

or protocols. While the details of these are best left up to the specific implementation, the 

ANSS policy should be to attempt to provide as much information in as standard a format 

as possible. 

2.3.5 Offline or Manual Review 

The ANSS must support multiple levels of product review and analysis. Although 

"review" is probably a continuous process, it is possible to distinguish two types. The 

first is the rapid review of alarm events, while the second is the typical "post-earthquake" 

analysis. 

Rapid review is performed immediately following an alarm and must be completed 

within a few tens of minutes after the origin time of the earthquake, with the goal of 

insuring the completeness and correctness of the rapid notifications. Corrections and 

updates to the automatic notification messages will be made through routine rapid 

review, typically performed at production data outlets. 

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Post-earthquake analysis is typically completed between tens of minutes to days to weeks 

(in some exceptional cases), with the goal of improving the automatic solution, using all 

possible data, and producing the most comprehensive and uniform data summary for an 

event. The continuum between rapid review and post-earthquake response is the periodic 

update of products as additional information becomes available. Post-earthquake analysis 

will be performed at production or other information outlets. 

2.4 References 

Report of the Network Architecture and Interconnection Subcommittee, 

http://quake.geo.berkeley.edu/anss-nai/, 55pp. 

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3 Instrumentation 

3.1 Introduction 

USGS Circular 1188 recommends that the ANSS include permanent and portable 

instrumentation. However, the portable instrumentation recommended represents less 

than 1% of the ANSS network. Herein, the TIC recommends standards to be used in 

procuring the basic instrumentation that will sense ground motion and store the resulting 

signals in a local data acquisition system (DAS) for the permanent broadband (national 

and regional) and urban monitoring (structures, reference and free field) deployments. 

Methods for handling the data flow upstream from the DAS are defined and described in 

Chapter 2. Those recommendations will influence some aspects of the communication 

and networking protocols in the DAS. 

Siting and installation procedures for the sensors and acquisition hardware are described 

in Chapter 4. There may well be constraints on size, packaging, power, and other factors, 

imposed by those standards or recommendations. 

3.2 Approaching the Problem 

A basic assumption underlying ANSS instrumentation recommendations is that issues are 

addressed from the framework of existing technology. Some ANSS-specific 

requirements may encourage new developments, and they will be incorporated insofar as 

they are feasible and cost-effective. In addition, an attempt was made to specify as few 

different types of instruments as possible. This approach may over-specify instruments 

in some settings increasing capital costs, but reduces maintenance costs in the long run by 

decreasing the size of the spares pool and the number of different types of instruments 

that must be maintained. It may be possible to achieve significant capital cost savings 

with little or no loss of capability by relaxing specifications for certain environments 

(e.g., reference stations in noisy urban areas). Early consideration must acknowledge the 

different instrumentation systems that will make up ANSS, as summarized in the 

following. 

3.2.1 National stations 

• Meet the needs of national and global monitoring. 

• High resolution in the band 0.01 to 15 Hz, on-scale recording, and latencies less 

than about 30 s. 

• Meet the needs of national and global earthquake research. 

• Resolution below ambient noise in the band 0.04 Hz to 10 Hz, on-scale recording, 

high fidelity, and complete continuous data. 

• Capture strong ground motion where generated by large nearby events. 

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• Sensitivity in the band 0.02 to 50 Hz, a clip level of 4 g, constant absolute 

sensitivity, and low hysteresis. 

3.2.2 Regional stations 

• Meet the needs of local and regional monitoring. 

• High resolution in the band 0.02 to 35 Hz, on-scale recording, and latencies less 

than about 10 s. 

• Meet the needs of regional scale seismological research. 

• Resolutions below ambient noise in the band 0.04 to 10 Hz, on-scale recording, 

high fidelity, and complete continuous data. 

• Capture strong ground motion where generated by large nearby events. 

• Sensitivity in the band 0.02 to 50 Hz, a clip level of 4 g, constant absolute 

sensitivity, and low hysteresis. 

3.2.3 Free field and reference stations (non-structural installations) 

• Provide information about the strong motion wave field and local site effects with 

little (reference) or no (free field) contamination from major structures. 

• Sensitivity in the band 0.02 to 50 Hz, a clip level of 4 g, constant absolute 

sensitivity, low hysteresis, and latencies less than about 10 s. 

3.2.4 Structural arrays 

• Provide information about the response of a structure to strong ground shaking. 

• Requires sensitivity in the band 0.02 to 50 Hz, a clip level of 8 g, constant 

absolute sensitivity, low hysteresis, and latencies of approximately 10 s. 

• Consider the use of emerging technology to measure the response of structures 

(i.e. Electronic Distance Measuring (EDM) or Global Positioning System (GPS) 

devices to measure structural displacements directly). 

3.3 General Goals & Expectations 

Data delivery must be reliable and suitable for a variety of communications technologies. 

Equipment must operate reliably over long periods of time (at least 10 years) in hostile 

environments (extreme temperatures, moisture, "dirty" power, and pests). 

3.3.1 Bandwidth 

Bandwidth goals for national stations are based on USNSN specifications. The low 

frequency specification is based on research needs while the high frequency specification 

is limited by attenuation over distances comparable with the inter-station spacing. 

Bandwidths for regional and strong motion stations are based on observed practice. 

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3.3.2 Sensitivity & dynamic range 

The clipping levels are true maximum ground motions that are to be recorded within 

specifications. 

3.3.3 Data latency 

Short latencies for free field and reference stations are to support "shake map" generation. 

Latencies for structural arrays are based on the need for rapid assessment of structural 

damage (especially for critical structures). 

3.4 General Design Concepts 

Some basic decisions about the behavior of ANSS stations either have or can be made a 

priori based on experience, technological trends, and the stated goals of the ANSS. 

• The need for wide bandwidths and linear high dynamic range probably dictate 

feedback sensor designs. 

• The need for high resolution dictates on-site digital recording and digital telemetry. 

• Seismological research and engineering practice and research require three 

component data. 

• Technological trends suggest standardizing on Internet protocols (IP). 

• Strong motion data should have continuous access to telemetry when ever possible. 

• Sites with limited telemetry bandwidth will be accommodated by event segmented 

strong motion data, compressing all data, and adopting the lowest sample rates 

consistent with requirements. 

• The need for complete data suggests on-site storage for all types of stations. 

• Reliable communications requires error correction and packet retransmission, which 

requires bi-directional communications. Variable communications latencies require 

on-site timing. 

• Small data delivery latencies require short packets and reasonably fast 

communications speeds with minimal routing/buffering delays. 

The combination of on-site storage and short latencies requires that old data be caught up 

while current data flows uninterrupted. That is, after a communications outage, older 

data should be transmitted in time sequential order in parallel with the real-time data but 

at a lower priority. 

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3.5 Functional Specifications 

The specifications for national and regional seismometers are sufficiently similar that 

they could both be satisfied by the same sensor. This is reflected in the following 

specifications (e.g., the high and low frequency specifications have been extended for the 

national and regional seismometers respectively). If different national and regional 

seismometers are chosen (e.g., for cost reasons), these specifications should be modified 

by making the national seismometer bandwidth 0.01 to 15 Hz and the regional 

seismometer bandwidth 0.02 to 35 Hz. 

Free field, reference, and structural instruments are judged to have similar enough 

requirements that they are considered together. The primary difference seems to be that 

free field and reference stations will require three components while structural arrays 

require elements that may be from one to three components and multi-channel recording 

systems. 

The specifications call for the sensors and the DAS to be able to report model specific 

information such as nominal transfer function and device specific information such as 

serial number and sensitivity. Because this is a feature that is not available in current 

equipment, the ANSS will need to work with vendors to see it implemented in an 

acceptable form. 

3.5.1 National station 

3.5.1.1 Seismometer 

• Three orthogonal component differential outputs with a response nominally flat to 

velocity in the band 0.01 Hz to 35 Hz (amplitude response may be 3 dB below the 

peak response at 0.01 Hz and at 35 Hz). 

• Non-coherent noise floor at least 3 dB below the ASL New Low Noise Model 

(NLNM) in the band 0.05 Hz to 10 Hz. Non-coherent noise within 10 dB of the 

NLNM between 0.01 Hz and 15 Hz and within 20 dB of the NLNM between 15 

Hz and 35 Hz. 

• Dynamic ranges of at least 155 dB in the range 0.01 to 0.05 Hz, 150 dB in the 

range 1 to 10 Hz, and 140 dB in the range 10 to 15 Hz (see Appendix C). 

• Nominal distortion less than -80 dB and nominal cross axis coupling less than -40 

dB. 

• Operating temperature range of 0 to 40 degrees C. Instrument sensitivity shall 

remain within +/-5% of nominal value over entire temperature range. Output 

offset and mass position voltages shall remain within operating limits for a +/-10 

degree C temperature change. 

• Transfer function shall be supplied with each instrument and shall be accurate to 

within 1% in amplitude and 4 degrees in phase over the pass band of the 

instrument. 

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• Instrument response after being over-driven (clipped) shall return to normal linear 

operation within 5 minutes after being over-driven by ground motions or 

calibration signals at or above the clip level of the instrument. 

• Calibration input and remote lock/unlock, mass center, calibrate enable functions. 

• Mass position outputs for each sensor component. 

• Instrument output shall be unaffected by reasonable changes in magnetic field and 

atmospheric pressure and reasonable levels of radio frequency interference (see 

Appendix C). 

• Instrument shall be designed for a 10-year (minimum) life and shall be 

demonstrated to have a 40,000 hour (minimum) mean time between failures (see 

Appendix C). 

• Power consumption shall not be greater than 1 watts at 12 VDC (operational 

mode, leveling and/or mass centering motors not running). 

• Sensor must provide the following information to the DAS on request (see 

Appendix C): 

• Manufacturer name 

• Sensor type 

• Sensor serial number 

• Factory calibration parameters including nominal poles and zeros response. 

3.5.1.2 Accelerometer 

• Three orthogonal component differential outputs with a response flat to 

acceleration in the band 0.02 to 50 Hz. 

• Clip level of 4 g. 

• Dynamic range of at least 145 dB in the range .02 to 2 Hz and at least 130 dB in 

the range 2 to 50 Hz and at (see Appendix C). 

• Nominal distortion less than -60 dB and nominal cross axis coupling less than -40 

dB. 

• Operating temperature range of -20 to +60 degrees C. Instrument sensitivity and 

output offset shall remain within 1% of nominal value over a temperature range of 

0 to 40 degrees C and within 2% over entire temperature range. Gain stable to 

1% under all conditions. 

• Transfer function shall be supplied with each instrument and shall be accurate to 

within 1% in amplitude and 4 degrees in phase over the pass band of the 

instrument. 

• Hysteresis in acceleration offset shall be less than –100 dB referenced to full scale 

under all conditions. 

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• Calibration input, remote calibration enable function, and manual offset 

adjustment, which shall be lockable to prevent non-linear effects. 

• Instrument output shall be unaffected by reasonable changes in magnetic field and 

atmospheric pressure and reasonable levels of radio frequency interference (see 

Appendix C). 

• Instrument shall be designed for a 10-year (minimum) life and shall be 

demonstrated to have a 40,000 hour (minimum) mean time between failures (see 

Appendix C). 

• Power consumption shall not be greater than 1 watt in operational mode at 12 

VDC. 

• Sensor must provide the following information to the DAS on request (see 

Appendix C): 

• Manufacturer name 

• Sensor type 

• Sensor serial number 

• Factory calibration parameters including nominal poles and zeros response. 

3.5.1.3 Data Acquisition System 

• Six-channel, 24-bit format analogue-to-digital converter (ADC) with differential 

input range matched to the sensors. Resolution shall be at least 23 bits from 0.01 

to 15 Hz and at least 21 bits from 15 to 50 Hz (see Appendix C). 

• The sensitivity of each digitizer channel (counts per volt) shall be accurate to 

0.1% or better at DC (0 Hz). 

• External time reference accurate to 1 ms absolute and a free running oscillator 

with a maximum temperature sensitivity of 0.1 ppm/degree C and a maximum 

drift rate (at constant temperature) of 0.1 ppm/day. 

• Data samples on all channels running at the same sample rate shall be taken 

simultaneously to within 1% of the sample interval. 

• Operating temperature range of -20 to +60 degrees C. Sensitivity stable to 1% 

over range 0 to 40 degrees C and to 2% over entire temperature range. 

• Capable of generating control signals matched to sensors, such as lock/unlock, 

mass center, calibrate enable, initiate ring-down or free period test, damping test, 

etc. Capable of generating step, sine, and random binary telegraph calibration 

signals configurable to provide sensor outputs between 5% and 50% of full scale. 

• All channels shall be derived from raw digitizer sample rate using linear phase 

“brick-wall” filters with high frequency corner fc at least 80% of the Nyquist 

frequency and stop band amplitude (Nyquist to higher frequencies) at least 120 

dB below the pass band. Pass band (DC to fc) ripple shall be less than 5%. 

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• Capable of sampling continuous 3-component data from the primary sensor at up 

to 100 samples/s. Capable of sampling 3-component data from the secondary 

sensor at up to 200 samples/s. Capable of providing multiple simultaneous sample 

rates from broadband and strong motion sensors. 

• Capable of detecting, and storing on local storage media, events on all channels of 

each sensor, flagging events in the continuous data from the primary sensor, and 

buffering triggered data for transmission from the secondary sensor. 

• Capable of providing state-of-health (SOH) monitoring including mass position, 

internal temperature and voltages, external voltages (e.g., AC and batteries), 

absolute time quality, and latitude, longitude, and elevation (if a GPS clock is 

used). SOH parameters shall be available in continuous telemetry packets for 

ease of monitoring SOH without special requests. 

• Capable of data compression at all sample rates. Packets will have a maximum 

length of 1000 samples to provide adequate latency. 

• Data telemetry must be error corrected, must support standard IP communications 

protocol(s), must support a variety of communications technologies, and must be 

capable of transmitting backlogged and triggered data without interrupting realtime data delivery. 

• Capable of buffering a minimum of 7 days of seismic data (in the event of a 

telemetry outage) in on-site storage media. 

• Instrument output shall be unaffected by reasonable changes in magnetic field and 

reasonable levels of radio frequency interference (see Appendix C). 

• Instrument shall be designed for a 10-year (minimum) life and shall be 

demonstrated to have a 40,000 hour (minimum) mean time between failures (see 

Appendix C). 

• Power consumption: Not greater than 1 watts average, 2 watts peak at 12 VDC. 

• Capable of acquiring sensor configuration parameters (i.e., manufacturer name, 

sensor type, sensor serial number, and factory calibration parameters) from both 

the seismometer and accelerometer and external power system (e.g., battery 

charger, UPS, or solar array) configuration and status as specified in Appendix C. 

• Configuration information stored in each DAS should allow reconstruction of the 

complete DAS transfer function for all active data streams. Configuration 

information should include: 

• Manufacturer name 

• DAS type 

• DAS serial number 

• Board serial numbers and version numbers 

• Factory calibration parameters including: 

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ANSS TG v 1.0 

• Nominal poles and zeros response if applicable 

• Fir filter coefficients 

• A/D conversion factors for each channel 

3.5.1.4 Power System 

• Provide backup 12 VDC power to sensors, data acquisition system, and 

communications equipment for a minimum of 7 days in the event of main power 

source failure. For planning purposes, the power consumption of a national or 

regional station (six components) would average less than 3 W and a strong 

motion station (three components) less than 2 W exclusive of the communications 

system. 

• Provide surge suppression, filtering, and stable 12 VDC output from AC mains 

with an input range of 90-130 VAC. 

• Provide auto-cutoff of DC output voltage when it falls below 10.5 VDC to avoid 

damage to batteries or equipment. 

• Provide state-of-health (SOH) monitoring to the DAS on request (see appendix C) 

including: 

• Manufacturer 

• Model 

• Input voltage 

• Internal alarm conditions 

3.5.2 Regional station 

3.5.2.1 Seismometer 

• Same as for national station. Note that linear phase FIR filters are known to 

create acausal artifacts that can cause problems for automatic picks from 

stations very near to an event. Despite this drawback, the IS recommends that 

linear phase filters should be used for regional stations because of the 

enhanced value for later research. The IS suggests that acausal artifacts can 

be reduced to acceptable levels for real-time processing by attenuating high 

frequency energy using minimum phase filters. 

3.5.2.2 Accelerometer 

• Same as for national station. 

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3.5.2.3 Data Acquisition System 

• Same as for national station, except: 

• Data buffering for 6 hours instead of 7 days. 

3.5.2.4 Power System 

• Same as for national station. 

3.5.3 Strong motion station (free field and reference) 

The accelerometer, the DAS, and the power system in this case shall be delivered as an 

integrated system, even though these three items may be physically separate modular 

units connected together with cables. The inter-module cables, with connectors, shall 

also be delivered as part of this integrated system. Cable lengths will be specified at the 

time the order is placed, and will be specific to each site. It is likely that a standard cable 

length will be appropriate in most cases. 

3.5.3.1 Accelerometer 

• Same as for national station. 

3.5.3.2 Data Acquisition System 

• Same as for national station, except: 

• Resolution of 21 bits in the band .02 to 50 Hz. Note that with 21-bits of 

resolution and a 4g sensor, theoretically a magnitude 2.5 event at 10 km 

should be well recorded and empirically a magnitude 1.8 event at more 

than 35 km can be recorded well enough to determine the peak 

acceleration. That is, ambient noise is likely to be the limiting factor in 

station performance, not the 21-bit resolution. 

• 3 channels (minimum) instead of 6. 

• A maximum sample rate of at least 200 samples/s. 

• Capable of on-site storage of a minimum of 2 hours of triggered data 

indefinitely in non-volatile memory (instead of 7 days continuous data). 

3.5.3.3 Event detector 

• Shall be triggered by accelerations from 0.0008g up to 4g. 

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3.5.3.4 Power System 

• Same as for national station. 

3.5.4 Strong motion station (structural) 

The accelerometer and its power system and the DAS and its power system shall be 

delivered as integrated subsystems, even though these items may be physically separate 

modular units connected together with cables. The inter-module cables, with connectors, 

shall also be delivered as part of this integrated system. Cable lengths will be specified at 

the time the order is placed, and will be specific to each site. It is likely that a standard 

cable length will be appropriate in most cases (between components at one location). 

Note that cables between the accelerometer and the DAS are not included. Wireless 

technology will be considered to allow easy distribution of sensors throughout an existing 

structure provided that it can be shown to be sufficiently reliable. 

3.5.4.1 Accelerometer 

• Same as for reference station, except: 

• Must be available in 1, 2, and 3 component packages 

• Must have an option for a clip level of 6g instead of 4g with a gain stability of 

3%. 

3.5.4.2 Data Acquisition System 

• Same as for reference station, except: 

• Must be available in configurations including 3 to 24 channels. 

3.5.4.3 Power System 

• Same as for reference, except: 

• Power must be available at each accelerometer and at the central multi-channel 

DAS. 

3.6 System Packaging 

Vendors may address some of the specifications above including RFI, magnetic, and 

pressure shielding through equipment packaging. In addition, packaging will meet the 

following requirements: 

• All equipment: 

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ANSS TG v 1.0 

• Operate in 100% relative humidity. 

• Survive temporary shallow submersion in water (see Appendix C). 

• All seismometers and accelerometers: 

• Provided with leveling legs. 

• Structural strong motion station: 

• Accelerometer plus data power system shall not weigh more than 25 pounds. 

3.7 Evaluation of Competing Systems 

• RFP must be written with testable specs (see Appendix C) 

• Sensor dynamic range shall be computed according to the recommendations 

of the Standards for Seismometer Testing Workshop, July 1989 

• Digitizer resolution computed according to the Modified Noise Power Ratio 

test. 

• Manufacturers shall provide their own test results 

• Pre-productions or prototype units provided during evaluation phase of contract 

will be fully tested 

• Production units must also comply with specs and will be spot checked at random 

to assure compliance (using a subset of acceptance tests) 

3.8 Data Format 

At a minimum, data packets (both seismic and SOH) generated by the DAS shall include 

information that: 

• Uniquely identifies the station and channel 

• Provides information needed to decode and use the data including: 

• Data type and format 

• Packet length 

• Record number 

• Time correction 

In addition, the DAS shall be capable of formatting the manufacturer, equipment type, 

serial number, and metadata (e.g., response information) for the DAS and collocated 

sensors and power equipment for occasional transmission. The goal is to make field 

equipment as self documented as possible. Note, however, that it must be possible for the 

ANSS processing system to override erroneous metadata collected from the field if 

necessary. 

3.9 Station Architecture 

The above specifications seek to make DAS and sensor equipment self identifying and 

capable of providing their own response metadata. It also seeks to provide SOH 

information from the DAS (e.g., location), sensors, and power system (e.g., power 

history). The model specified places the DAS in the central role of collecting the 

identification, metadata, and SOH information from all other subsystems and integrating 

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ANSS TG v 1.0 

it in a single data stream to the outside world. In addition, the roles of metadata and SOH 

information have been specified in an arbitrary fashion (e.g., AC voltage has been 

specified as an SOH stream derived by the DAS, but it could also be metadata provided 

by an UPS). In fact, other models are possible and may be advantageous (e.g., DAS, 

sensors, and power system all reporting through a separate communications controller). 

In practice, any functionally equivalent station architecture will be considered. 

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4 Siting and Installation 

4.1 Introduction 

Seismic instrumentation provides data that serve three primary purposes: 

• Rapid response to potentially damaging earthquakes, 

• Seismic monitoring, and 

• Seismological and engineering research. 

Traditionally, siting and installation have been designed to provide good coverage of 

geological and manmade structures of interest and good recordings of events of interest. 

Coverage implies that events are recorded at a range of azimuths and distances adequate 

to derive required products and structures are instrumented adequately to understand their 

dynamic deformation. As a trivial example, accurate hypocentral determination requires 

good azimuthal coverage and ideally a range of distances including very close stations. 

Good recordings require seismically quiet sites, good coupling with the bedrock, and 

highly sensitive seismometers and recording equipment. Engineering studies require 

strong motion information around and throughout structures. 

The ANSS is focused on upgrading traditional seismic instrumentation with state-of-theart broadband seismometers and accelerometers and high resolution (e.g., 24-bit) 

digitizers. Through the use of negative feedback technology, broadband sensors are 

capable of recording earth noise at a quiet site as well as large amplitudes with a high 

degree of linearity over a broad frequency band. However, to take advantage of the 

sensitivity and bandwidth of broadband sensors, it is necessary to consider traditional 

siting and installation issues as well as new issues such as thermal stability and tilts due 

to atmospheric pressure. 

4.2 Site Characterization 

Detailed understanding of the subsurface geology and soil/rock properties is important 

for understanding of the contribution of site response to measured ground motions and 

for the classification of measured ground motion parameters, particularly at strong 

motion reference stations. A good review of methods for site characterization is found in 

ASTM Standard D420-98 “Guide to Site Characterization for Engineering, Design, and 

Construction Purposes.” 

For ANSS broadband and strong motion reference stations, some level of site 

characterization studies should be required for every station. At a minimum, the surface 

geology should be determined and available site information from previous local or 

regional studies should be obtained and added to the station’s auxiliary information. 

Surface geology provides a primary description of the site and should be obtained from 

geology maps or observations by a knowledgeable person. Note that surface geology can 

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ANSS TG v 1.0 

be a poor estimator of subsurface soil or rock properties, especially for sites geologically 

classified as rock. 

In addition to thorough geologic descriptions, site-specific characterization information 

should also be obtained at strong motion reference stations. At a minimum, the 

NEHRP/IBC site class should be determined. The NEHRP/IBC site class is important for 

comparison of measured ground motions with building code seismic design levels. These 

site classes, denoted A-F, are formally described in the 2000 International Building 

Code’s seismic design provisions as follows: 

A. Hard rock with measured shear wave velocity V30>1500 m/s 

B. Rock with 760m/s<V30<1500m/s 

C. Very dense soil and soft rock with 360m/s<V30<760m/s 

D. Stiff soil with 180m/s<V30<360m/s 

E. A soil profile with V30<180m/s 

F. Soils requiring special investigations (liquefiable soils, sensitive clays, or very 

weak soils) 

V30 is the effective average shear wave velocity (1/average slowness) in the upper 30 

meters. NEHRP/IBC classes require some kind of measurement of V30. 

A more complete understanding of the contribution of site response to the measured 

earthquake shaking at a strong motion reference station will require a more complete 

subsurface site characterization. These additional detailed measurements are considered 

optional with respect to these guidelines, but are strongly recommended for all strong 

motion reference stations, whether on open ground, in small buildings, or in densely 

urbanized areas. 

4.2.1 Obtaining Existing Site Information 

Site characterization information is part of the station metadata and provisions must be 

made to maintain, archive, and distribute it along with other metadata. A literature search 

can be a very inexpensive source of information on site geology and even subsurface soil 

and rock properties. In most populated areas there will have been previous geological 

studies of the region and perhaps even local environmental, ground water, or planning 

studies. These can contain a wealth of information that will assist in site characterization. 

Potential sources of information on a regional basis are government geological or natural 

resources agencies. An example is the U.S. Geological Survey. For local studies, sources 

of information are the local government planning agency, local universities, private water 

companies, and even local water well drilling companies. If the strong motion station is 

near a building, it is possible that the construction documents will contain some soils 

reports. 

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ANSS TG v 1.0 

4.2.2 V30 Determination for NEHRP Categorization 

V30 (recommended for strong motion reference stations only) can be estimated using 

noninvasive surface methods, or can be directly measured using either a minimallyinvasive seismic cone penetrometer or more invasive drilling and logging methods. 

Drilling and logging methods have the added advantage that subsurface geology can be 

directly observed during drilling. 

Two available surface methods for estimation of V30 are surface wave methods and 

seismic refraction. Note that these methods are relatively inexpensive and can provide a 

good estimate of V30 at many sites when performed properly. However, these methods 

can and have provided erroneous or biased data at sites when improperly performed or 

when site characteristics are not optimal (i.e. not flat layering). One should be prepared to 

use one of the direct measurement methods if these indirect surface measurements are 

suspect at a site. 

A cone penetrometer (CPT, a metal probe pushed into the soil) is also an inexpensive 

way to obtain information about shallow (<30 meters) soils. If a “seismic cone” tool is 

used, shear wave velocity can be directly measured using a method equivalent to the 

downhole method. While the seismic cone does provide accurate measurement of the 

shallow shear wave velocity profile, it may be limited in depth of penetration at rock, stiff 

soil, or gravelly sites. It may not be possible to reach 30 meter depth and therefore not 

possible to accurately measure V30. 

V30 can be measured at all sites using a combination of drilling and shear-wave velocity 

logging. Drilling can be done using the auger method if the soils are relatively soft; this 

will be less expensive. In many cases, however, the rotary method (mud or air) will be 

needed to reach 30 m depth. If desired, drive-type (SPT) sampling can be done to obtain 

disturbed samples for determination of site lithology. [For more information, see Isihara, 

K., Soil Behavior in Earthquake Geotechnics: Oxford Engineering Science Series, No. 

46, Clarendon Press; ISBN 0198562241, 1996.] 

4.2.3 Detailed Subsurface Investigations 

Obtaining the most complete site characterization of a strong motion station will require 

drilling of an exploratory borehole, obtaining high-quality geotechnical samples for 

laboratory testing, and borehole geophysical logging. 

A detailed site investigation can consist of: 

• Drilling a borehole to the depth of “engineering rock” (Vs>750m/s) 

• Lithology logging during drilling 

• Obtaining samples for laboratory testing 

• Seismic velocity logging 

• Laboratory testing of samples for index properties 

• Laboratory testing of samples for nonlinear properties 

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ANSS TG v 1.0 

These investigations can be a major effort, requiring heavy equipment and expensive 

measurements and laboratory testing. 

4.3 Station Documentation 

A new or existing ANSS station should be well documented. A user of the recorded 

waveform data or derived parameters should be able to obtain all of the metadata needed 

to identify the station, its instrumentation, its station configuration/construction, its site 

conditions, and any other information which might have an effect on the data. 

4.3.1 Basic Station Data 

The basic documentation of a station should include the following, defined as the Basic 

Station Data: 

• Station identification (name, ID number, etc.) 

• Station location (coordinates, location description within site; detailed 

information may need to be protected in the property owner's interests) 

• Station access information (contacts, keys, etc.; may be protected information) 

• Station construction (type, description) 

• Site geology 

• NEHRP/IBC category/V30 value (strong motion reference only) 

• Station instrumentation details 

• Station calibration data 

• Station history (installation date, modification descriptions/dates, etc.) 

•Ambient noise spectra (national and regional broadband sites only) 

These data must be available in two forms: an online database and an archival 

distribution media. 

4.3.2 Auxiliary Station Information 

Other information about a station that should be documented includes: 

• Photographs of the station construction 

• Photographs of the station instrumentation installation 

• Photographs of the station vicinity (showing nearby buildings, topography, or 

other features) 

• Site map 

• Plots/numeric data for site characterization information 

• Other descriptive information about the site 

As for the Basic Station Data, the Auxiliary Station Information must be available in two 

forms: an online database and an archival distribution media. 

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4.4 National and Regional Stations 

USGS Circular 1188 specifies that the ANSS national stations are to be distributed as 

uniformly as possible across the US. The primary frequency band of interest is 0.01 to 15 

Hz. Higher frequencies are not of interest because propagation distances are typically 

less than the mean inter-station spacing (~300 km). At the long period end, the national 

backbone can provide higher spatial sampling to complement the even longer period 

instrumentation of the Global Seismograph Network (GSN) for continental scale 

structural studies as well as improved coverage for long period source studies. Note that 

the ANSS plan calls for a backbone of 100 stations of which 80 would meet ANSS 

specifications and 20 would meet GSN specifications. GSN stations have similar 

requirements to the ANSS backbone stations except that there is interest in periods as 

long as 100,000 s. 

Locations of the regional broadband stations are the responsibility of the regional 

working groups and will not be discussed further here. The primary frequency band of 

interest is 0.05 to 35 HZ. At the high frequency end, small events very close to the station 

are of interest. At the long period end, fundamental and higher mode surface waves 

should be recorded. 

The siting and installation requirements for both national backbone and regional 

broadband stations will be considered in the following. Although the requirements for 

these elements of the ANSS are somewhat different, as discussed below, their siting and 

installation have much in common. The common elements and concerns are described in 

the following subsections. 

4.4.1 Network Design 

Seismic network design is always a compromise between network goals and funding. 

The ANSS has chosen high resolution, broadband sensor technology that establishes the 

cost of each station. Funding then limits the number of stations available to meet 

program goals. This situation is further complicated by the multiple uses most networks 

serve. For example, rapid response requires sensors near urban areas while monitoring 

requires some coverage in areas of low to moderate seismicity. Similarly, sensors near 

seismic zones are needed for some research projects while other research requires more 

uniform regional coverage. 

Ultimately, the success of a network design depends on the ability of the network to 

produce the products required with the desired accuracy and timeliness. To some extent, 

this can be modeled theoretically. For example, the timeliness and accuracy of 

earthquakes in known locations can be tested. Of course, these results must be used with 

caution as station performance can be highly variable (short period noise can easily vary 

by 40 dB from site to site) and difficult to predict. Thought must also be given to the 

problem of network utility at various stages of completeness. Even with adequate 

funding, networks installation is typically performed over a number of years, and 

(broadband) network uptime rarely exceeds 90% in practice. 

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4.4.2 Seismic Noise 

Over the frequency band of interest to the ANSS (~0.01 to 35 Hz), seismic noise falls 

into three distinct regimes. At high frequencies (0.5 to 35 Hz), seismic noise is 

dominated by wind, running water, and cultural effects. Wind couples into the ground 

through trees, towers, antennas, structures, and even rough topography. Rapids and 

waterfalls couple into the ground directly, Cultural noise is generated by cars, trains, 

airplanes (on the ground), mining, manufacturing, and agriculture. In fact, almost 

anything people do in their daily lives contributes to cultural noise. 

At mid-frequencies (0.05 to 0.5 Hz), seismic noise is dominated by surface waves 

generated by ocean waves breaking on shorelines. This so-called 6-second microseism 

peak is huge (at least 20 dB above the high frequency noise and 40 dB above the long 

period noise). Although the microseisms are significantly larger near the ocean, they are 

a pervasive, worldwide phenomena. 

Long period noise (0.0001 to 0.05 Hz), is dominated by tilt noise due to thermal and 

atmospheric pressure effects. This counter intuitive result is due to the sensitivity of 

broadband sensors to nanoradian tilts. Thermal effects include the differential heating of 

structures or even rough topography inducing small deformations. Passing weather fronts 

differentially deforming the ground similarly induces pressure tilts. 

4.4.3 Site Selection 

The best sites are located on (or even better, in) hard, uniform, competent bedrock; 

remote from populations centers, heavily traveled roads, train tracks, and heavy industry; 

and away from trees, antennas, buildings, rapids, and windy locations such as mountain 

peaks or saddles. Needless to say, these conditions are difficult to achieve and most 

seismic sites are a compromise between network design goals and site characteristics. 

This problem becomes even more difficult when power, communications, access, and 

security are considered. 

Seismic noise is heavily influenced by local geology. Installation on unweathered 

bedrock is best. Harder rock provides a higher signal to noise ratio and less complex 

geology provides less distortion in propagating waves, particularly at higher frequencies. 

However, weathered bedrock and well-consolidated sediments can also make useful 

seismic sites. Generally, softer, low impedance material amplifies both signal and noise, 

but results in a net loss in the signal to noise ratio. Softer materials are also much more 

prone to long period tilting, particularly due to thermal effects. Poorly consolidated 

material generally makes a poor seismic site and should be avoided if possible. 

Geologic, topographical, and political maps can be useful for preliminary siting work. 

Geologic maps help to determine if outcrops are available and what types of bedrock 

might be encountered. Topographical maps can provide a feeling for the roughness of 

the terrain, vegetative cover, and accessibility. Political maps can provide a guide to 

natural and cultural noise sources. Local seismic network experience can also be 

invaluable. 

Once preliminary sites are selected, they must be surveyed for suitability based on 

potential local noise sources, accessibility, availability of power, communications drops 

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or lines-of-site, security, and property ownership. Finally, it is important to operate 

broadband portable instruments with 24-bit recording at the most promising sites to 

determine the best ones empirically. It is necessary to use broadband instrumentation and 

to record for at least a day or two at each site to determine both the long and short period 

site noise characteristics because good short period sites are often poor long period sites 

and vise versa. Shallow seismic profiling can be useful in determining the complexity of 

the subsurface geology and the depth to competent bedrock. 

Although finding good seismic sites is never easy, there is hope because most noise 

sources are relatively high frequency and high frequency noise from surficial sources 

doesn't propagate very well. For instance, quite good performance is sometimes possible 

only a few kilometers from major highways and only 30 m from tall trees and antennas. 

For more information about siting see the New Manual of Seismological Observatory 

Practice (Bormann, 1999; http://www.seismo.com/ msop/nmsop/nmsop.html). For more 

information on the recommended distances from a variety of high frequency noise 

sources see the Manual of Seismological Practice (Wilmore, 1979; 

http://www.seismo.com/msop/msop79/msop.html). 

4.4.4 Installation Types 

Various types of installation in mines or caves and at the surface in vaults or smaller 

structures will be discussed. Boreholes can be useful for emplacing sensors into bedrock 

when no outcrops are available and for reducing long period noise. However, because of 

the high cost and typically low cost-benefit ratio, boreholes are not recommended for use 

in the ANSS. 

Although the cost of drilling a shallow tunnel can be prohibitive, abandoned mines and to 

a lesser extent caves can provide outstanding seismic sites. This is because underground 

sites are often in hard rock, are thermally stable, and to some extent isolated from 

pressure effects. However, underground sites can also be difficult because of owner 

liability (e.g., due to the dangers of rock falls, radiation, and other hazardous materials) 

and environmental issues (e.g., cave decorations and endangered species). Underground 

locations also require special considerations for moisture and long cable runs (for power, 

communications, and GPS antennas). Partitions with tightly fitting doors are sometimes 

used to minimize air circulation, and moisture can be controlled through the use of 

gunnite. 

By far the most common type of seismic installation, however, is at or near the earth's 

surface. Installations in buildings have not proven effective because buildings 

significantly distort the wave field and are not recommended. Recent work has shown 

that the massive WWSSN style vaults are not necessary for good long period 

performance. Existing vaults are useful, but it is not recommended that the ANSS build 

more. Rather two types of surface installation are recommended: 1) small buried vaults 

and 2) barrels or pipes. 

The small vault is typically a concrete structure containing an isolated pier with a surface 

area of about 1 square meter, room for electronics, and a small maintenance working 

space. The floor of the vault would typically be buried at least 2.5 m below the surface of 

the ground. The top of the vault should be buried at least 30 cm. If possible, the DAS 

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should be collocated with the sensors and the communications and power equipment 

should be placed in a separate enclosure (in either a shelter above the vault or in a 

subsurface room near the vault; see Hanka, 2001; http://www.gfzpotsdam.de/geofon/agu_pub/) 

The barrel or pipe installation is typically constructed using large diameter, commercially 

available, concrete or galvanized pipe or heavy, plastic, toxic waste barrels. Typically, 

the pipe or barrel is set into concrete so that the top of the enclosure protrudes about 15 

cm above the ground. The hole outside the enclosure is also filled with concrete. In this 

type of installation, the concrete at the bottom of the enclosure acts as the pier. The 

sensor must be placed deeply enough that the top of the insulating material above the 

sensor is still below the surface of the ground. If possible the DAS should also be placed 

in the seismic enclosure (see McMillan, 2001, USGS Open File Report, in preparation). 

Note that in this type of installation, the communications and power equipment are 

typically placed in a separate shed or enclosure away from the sensors. Note that barrel 

installations have also been used with some success in mines to provide thermal 

insulation and minimize convection. 

In all cases, the sensors are placed on a smooth concrete surface that is well coupled with 

the underlying rock. Bedrock is exposed by removing surficial soil and scraping off 

weathered material (preferably with a backhoe). The surface of the rock should be 

reasonably smooth and free of dirt before the concrete is poured. Chemicals that improve 

the adhesion of the concrete and resistance to moisture are often added. 

4.4.5 Minimizing Environmental Effects 

Environmental factors act on seismic stations by either directly affecting the sensor(s) or 

indirectly affecting the sensor(s) through interactions with the seismic enclosure. Factors 

considered include electromagnetic interference (EMI), magnetic fields, wind, 

temperature variations, and pressure fluctuations. All of these factors can directly effect 

the sensor. Temperature and pressure also act indirectly through the enclosure. 

High performance seismic equipment generally employs differential circuitry to reject 

common mode signals such as EMI. EMI also can be minimize by keeping the analogue 

signal cables between the sensor and the DAS as short as possible. Most broadband 

sensors are well shielded against magnetic and pressure effects by heavy external steel 

cases. However, seismometers vary widely in their thermal sensitivity. Some sensors 

can be driven onto their stops by temperature changes as small as a few degrees C while 

others can withstand an order of magnitude greater variation. Broadband sensors 

typically accommodate thermal variations by mechanically re-centering their masses. In 

most cases, this process can be automated and remotely commanded. However, the data 

are useless during the re-centering process, which can last for minutes to hours. 

Therefore, thermal stability is essential to the effective operation of seismic sensors. 

Choosing sheltered sites, using subsurface installations, and separating any aboveground 

shelter and antenna from the sensors can minimize wind noise coupling directly into the 

enclosure. Choosing sites in hard rock, with only moderate topography and sealed 

subsurface installations helps minimize pressure effects. In a vault installation, isolating 

the pier (which is firmly coupled to the bedrock) minimizes the effect of the vault tilting. 

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In a barrel installation, the whole subsurface structure is coupled to the bedrock and no 

isolation is necessary. Warpless baseplates developed for several very long period 

sensors have been shown to be effective at controlling the effects of very long period tilts 

due to pressure (e.g., Holcomb and Hutt, 1992, Open File Report 92-302, USGS or 

Hanka, 2001; http://www.gfz-potsdam.de/geofon/agu_pub/). 

Choosing a site out of direct sunlight (or installing a cover or low lean to roof over the 

sensors), burying the sensors, using concrete without aggregate or reinforcing steel (to 

avoid differential expansion), and using adequate insulating material can minimize 

thermal effects. The concrete pier (or barrel floor) should also be vibrated to remove 

entrained air bubbles that can also result in differential expansion. Because long period 

seismic signals (and very long period seismometers themselves) are sensitive to very 

small thermal variations, the insulation of sensors is a highly developed art. The experts 

recommend at least 10 cm thick foam insulation sealed all around the sensors with an R 

value of at least 35 (e.g., Uhrhammer, Karavas, and Romanowicz, 1997; 

http://www.seismo.berkeley.edu/seismo/bdsn/instrumentation/guidelines.html). Note that 

in a vault installation the insulation and supporting structure around the sensor(s) 

amounts to a vault within a vault. 

Because broadband seismometers are active, they dissipate a small amount of heat. 

Therefore, if the insulation is too good, the sensors can overheat. Also, the heat 

dissipation can result in thermal convection around the sensors. This is combated by 

keeping the thermal enclosure around the sensors as small as possible and by filling the 

enclosure with foam beads or with fine playground sand. Either material kills convection 

and contributes to thermal stability. Sand has also been observed to improve seismic 

coupling between the sensor and the pier and helps to keep high aspect ratio sensors 

upright during strong shaking. 

Surprisingly, 24-bit digitizers are also sensitive to thermal variations and to air 

convection, which can increase electronic noise. Generally, they are housed in sealed 

environmental enclosures. However, because DASs draw more power than sensors (3 to 

25 V), stabilizing their temperature is problematical. Low power DASs should be 

installed in the subsurface seismic enclosure if their size permits, but with less insulation 

than the sensors. Higher power DASs should be installed in a separate enclosure. 

Because of the environmental housing and their self heating, higher power DASs 

stabilize their own temperature to some extent, albeit at a rather high level (typically 35°

to 40° C). 

4.4.6 Installing the Equipment 

Installing the equipment requires consideration of: 

• seismic coupling 

• sensor orientation 

• electrical grounding 

• cabling 

• isolation of equipment that generates acoustic noise 

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Note that the location of the sensors must be determined to within 10 m referenced to the 

WGS84 datum. 

At low frequencies, the weight of the sensor is typically adequate to provide good 

coupling just by placing the sensor on the pier. However, coupling at frequencies above 

about 20 Hz is much more difficult as evidenced by spurious spectral bumps (probably 

due to the feet of the sensor chattering on the pier). Recommended coupling methods 

include surrounding the sensor with sand, potting the sensor(s) in plaster of Paris, or 

epoxying the feet of the sensor to the pier. Strong motion sensors should be attached to 

the pier with bolts or straps to avoid being overturned during very large accelerations. 

Seismometers should never be bolted or strapped to the pier because of the danger of 

contaminating small seismic signals. 

For near surface installations, experiments have shown that it is possible for a trained 

technician to orient sensors to about 1 degree from a compass heading (accounting for 

local magnetic declination and presuming no magnetic anomalies). To orient sensors in 

tunnels and deep vaults or to check the orientation of surface sensors a comparison of 

microseisms with a reference sensor at the surface has proven valuable (e.g., Holcomb, 

2001, USGS Open File Report, in preparation). This method can be highly accurate even 

with sensor separations of several kilometers because of the strength and long wavelength 

of the microseisms. 

Adequate grounding is essential to get the best performance from sensitive electronics. 

For example, a lack of grounding has been observed to increase the electronic noise in 

high performance digitizers. For electronic purposes, the grounding wires do not have to 

be very heavy. However, more substantial grounding wiring may be required if the 

equipment is equipped with internal surge suppression. The electronics should not be 

grounded into the same point as the A/C power if at all possible. 

It is also important to eliminate ground loops, as they can add significant noise to the 

seismic signal. It is best to ground all equipment to a common point. Care must be taken 

because sensors can also be grounded through the pier. One possibility is to install the 

sensors on a heavy glass plate mortared to the pier. This has the added benefits of 

providing a smooth level surface and acting as a moisture barrier. 

Electronic equipment installed in racks or on shelves should be tied down to avoid 

damage during large accelerations. Excess cable should be kept to a minimum. Sensor 

cables, in particular should be laid in gentle arcs on the vault floor or suspended to avoid 

any strain on the sensor. Improperly laid cables can introduce noise into sensors as they 

expand and contract. 

Equipment that generates acoustic vibrations such as transformers (e.g., in battery 

chargers) and fans in electronic equipment must be located at least 10 m away from the 

sensor. Ideally, power and communications equipment should be located in a separate 

enclosure (a small shed or fiberglass enclosure mounted on a concrete pad is often used 

for this purpose). Installation of such equipment on soft foam rubber at least10 cm thick 

can greatly reduce the acoustic coupling into the ground. 

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4.4.7 Protecting the Station 

Delicate seismic equipment must be protected from: 

• lightning and other power surges 

• flooding 

• vandalism 

• corrosion, dust, and mold 

• rodents and other pests 

It is possible, but generally expensive, to protect seismic equipment from direct lightning 

strikes (though the station will usually be taken down). Because direct lightning strikes 

are rare (at least through most of the US) and because the cost of seismic equipment is 

rapidly declining, heroic measures for lightning protection (e.g., massive grounding, 

Faraday cages, etc.) are probably not cost effective and are not recommended for the 

ANSS. It is worthwhile to avoid siting stations in high lightning risk locations (e.g., the 

tops of tall mountains). It is also worthwhile burying cable runs at least 20 cm below the 

ground to avoid attracting lightning. 

For stations operating from A/C power, surges due to nearby lightning strikes (or other 

sources) carried to the station through the power grid are a much more significant 

problem. Operating all seismic equipment from batteries and only using main power to 

charge the batteries has proven an effective solution to surges through the power grid. 

Surge protection built into most seismic equipment (given adequate grounding) is 

generally sufficient to protect the electronics from surges that make it through the 

batteries. 

Power in rural areas can have many problems other than surges including high or low 

voltages, phase discontinuities, and extended outages. A combination of batteries and 

DC-DC converters (built into most seismic field equipment) effectively deals with these 

problems. Because power is such a common source of station outages, it is worthwhile 

monitoring battery voltages as an aid to remote diagnosis. Monitoring A/C power is even 

more useful, but risky since it creates a direct path between the power grid and the DAS 

(bypassing the batteries). Also, field equipment should be equipped with low voltage 

cut-off circuitry to protect the batteries from complete discharge during extended power 

outages. 

Water in seismic vaults or electronics enclosures is also a significant problem, 

particularly if they are underground. Water typically gets into enclosures through the 

access cover, the floor, or the cable conduits. It is much less likely that water will 

penetrate the walls of the enclosure unless they are cracked. Any cracks or holes in the 

enclosure should be well sealed with concrete patch or silicon caulk. Dampness in vaults 

can be channeled away from equipment into a sump. In smaller enclosures the air can be 

dried using desiccant. 

Enclosure access doors, panels, or lids should fit tightly, be sealed with a gasket, and be 

designed to avoid water. Double doors or a low lean to roof over the vault (also useful as 

a sunscreen) can also be effective. The concrete used in the floor and pier of a vault or 

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floor of a barrel installation should be treated with chemicals that improve water 

resistance. If an isolated pier is used, the isolation gap should be filled with asphalt or a 

similar material to seal out water. Finally, cable conduits need to be tightly fitted through 

the enclosure wall and carefully sealed using gaskets or silicon caulk. The conduits 

themselves should be run downhill going away from the sensor enclosure and should be 

plugged with expanding (aerosol) foam insulation. Equipment other than the sensor 

should be installed above the floor (e.g., above the sensor insulation, on pallets or 

shelves, or onto walls) to avoid water damage. Note that sensors are usually hermetically 

sealed, but that their associated control electronics aren't always watertight. 

Sadly, vandalism can also be a significant problem at seismic sites. The best way to 

avoid vandalism is to make the station as unobtrusive as possible (e.g., by installing the 

equipment underground). Above ground enclosures should be out of sight from nearby 

roads and trails if possible. If above ground equipment (e.g., satellite or radio antennas) 

are likely to attract attention, other security measures should be taken. Camouflage, 

fencing, locks, and installation on public land or near rural dwellings can all be effective 

security measures. Note that the requirements for good security are diametrically 

opposed to the requirements for quiet sites. 

Steps taken to control flooding are also usually effective against dust, rodents, and other 

pests. Paradoxically, environments where flooding is not a problem (e.g., above ground 

electronics enclosures or tunnels) are often poorly sealed and are more prone to problems 

with dust and pests. Sealing enclosures and drying the air inside using desiccant can also 

combat corrosion and mold. Tunnels and large vaults usually offer a protected, thermally 

stable environment. However, it is still worth using enclosures (e.g., barrels, etc.) to 

protect the equipment from dust, mold, and pests. This is particularly true for any 

equipment that is not housed in its own environmental enclosure and to protect cable 

contacts from corrosion. 

4.4.8 Recommended Installation – National Stations 

Tunnel and small vault installations are recommended for the GSN specification national 

backbone stations because thermal stability is so critical to long period performance. 

Vaults should be buried at least 2.5 m and thick insulation should be installed. Warpless 

baseplates should be used if possible to minimize the effects of pressure fluctuations. 

DASs should be installed in the seismic vaults for thermal stability. Power and 

communications equipment should be installed in a separate enclosure at or near the 

surface. Note that the depth to unweathered bedrock dictates the depth of burial of 

seismic vaults. The maximum vault depth that may be used is determined by the strength 

of the vault and cost. Installations as deep as 5 m should be considered. 

Tunnel and barrel installations are recommended for the remainder of the ANSS national 

backbone stations. In most parts of the US, burial of 0.5 to 1 m is adequate and easily 

achieved using barrels or pipes. If possible, DASs should also be installed in a 

subsurface enclosure for thermal stability. Power and communications equipment should 

be installed in a separate enclosure. If barrels must be installed at the surface, they 

should be buried with soil or loose rock leaving about 15 cm exposed. For additional 

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protection from direct sunlight and thermal isolation, it is recommended that the barrels 

be covered with sloping door set into a wooden frame and filled with foam peanuts. 

4.4.9 Recommended Installation – Regional Stations 

Tunnel and barrel installations are recommended for regional broadband stations. In 

most parts of the US, burial of 0.5 to 1 m is adequate and easily achieved using barrels or 

pipes. If possible, DASs should also be installed in subsurface enclosures for thermal 

stability. Power and communications equipment should be installed in a separate 

enclosure. If barrels must be installed at the surface, they should be buried with soil or 

loose rock leaving about 15 cm exposed. 

4.5 Urban Stations 

The siting and installation requirements for free field, reference, and structural recording 

are described in the following. 

4.5.1 Important Issues in Station Siting and Design (Non-Structural) 

Perhaps the three most important technical issues related to the topic of non-structural 

strong motion station siting and design are: 1) minimization of effects of structures on 

recorded motions; 2) design of the instrument foundation to minimize its effect on 

recorded motions; and 3) the need for characterization of the station site. Background for 

these three issues is briefly summarized below. 

4.5.1.1 Building Foundation Motions 

A goal of strong ground motion measurements is to accurately record the combined 

effects of earthquake source, propagation path, and geological/geotechnical site effects at 

a particular location within the range of amplitudes (<0.001 to 2g) and frequencies (0 – 

50 Hz) needed for the various alerting, assessment, and research applications. Localized 

effects on the measurements of man-made features of the particular location, including 

the station itself, should be minimized. Earthquake ground motions near a building may 

be affected by the interaction between the structure and the soil. Therefore, in an urban 

area it may not be possible to find a completely uncontaminated site for a strong motion 

station. The concept of an Urban Reference Station, as opposed to a Free-Field station, 

accepts this characteristic. 

4.5.1.2 Instrument Foundation Motions 

When a strong motion station is located away from buildings on soil, it will have its own 

small foundation for supporting the recorder and/or sensor. The instrument foundation 

can affect the recorded motions at high frequencies, and if the soil is soft, at frequencies 

as low as 10 Hz. ANSS and other strong motion station designs, especially those on open 

ground, should consider this issue of instrument foundation response and strive to create 

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a station that has horizontal and vertical transmissibilities of 1.0 over the 0 – 50 Hz 

frequency range. 

4.5.1.3 The Need for Site Characterization 

The engineering properties of the soil or rock under a strong motion station can have a 

large effect upon the recorded motions. Most strong motion network operators do not 

routinely perform extensive site characterization studies for their new stations; the main 

reason is the cost of such studies. Strong motion station sites are often characterized by 

the surface geology. The recent ROSRINE project (http://geoinfo.usc.edu/rosrine) has 

shown that surface geology alone can be a poor predictor of subsurface engineering 

properties. A detailed understanding of the subsurface geology and soil/rock properties at 

a strong motion station is important for understanding of the contribution of site response 

to the measured ground motions. Site characterization studies are needed at every ANSS 

strong motion reference station. 

4.5.2 General Siting Criteria 

Locations of ANSS free-field, reference and structural response stations shall be 

prioritized within a system of global priorities considering the following issues: 

• Desired density of coverage 

• Locations of existing stations – consider regions with inadequate coverage based 

on the desired density of coverage 

• Probability of shaking – consider the highest likelihood of shaking, both short 

period and long period 

• Probability of property damage – consider areas with elevated risk due to the type 

or number of structures or facilities 

• Probability of loss of life and indirect losses – consider areas with elevated 

probability of loss because of increased likelihood of casualties, death or human 

suffering due to the fragility of the infrastructure 

• Probability of learning – consider areas of major uncertainty in knowledge about 

earthquake generation, seismic wave propagation, ground motion attenuation, or 

site response in order to improve the understanding of the hazard in those areas 

• Value for emergency response – consider locations of strategic value for 

providing effective ground shaking information for emergency response 

4.5.3 Reference Stations on Open Ground (Free Field Stations) 

Ideally, an urban strong motion reference station (either the entire station or just the 

sensor) will be installed on open ground in an attempt to minimize contamination of the 

recorded motions by structural response. This section contains siting criteria, a discussion 

of siting issues, and recommended station designs for strong motion reference stations on 

open ground. 

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4.5.3.1 Siting Criteria 

A strong motion station located on open ground will be considered a “Strong-Motion 

Reference Station: Open Ground” (SMRS-OG) if it meets the following criteria: 

• It is not sited on locally anomalous soft or hard soils that might create ground motions 

not expected to be experienced by nearby sites of interest; 

• It is not sited in or on a localized topographic feature such as a hill, ridge, or valley 

that might create ground motions not expected to be experienced by nearby sites of 

interest; 

• It is located a distance of at least one major structural dimension (height or length, 

whichever is greater) from any large building (>4000ft sq. ft in plan or >2 stories in 

height) or any building with a significant basement or foundation; 

• It is located a distance of at least one major structural dimension (height or length, 

whichever is greater) from any non-building structure likely to cause significant soilstructure interaction effects that will contaminate the data; and 

• Station construction is designed to minimize soil-structure interaction in the 

frequency range 0.02 – 50 Hz. 

4.5.3.2 Siting Issues 

There are many issues to be considered in the location of a strong motion station. Perhaps 

the most important issues are those of site availability, permission, and permitting. A 

discussion of these issues and many other siting issues is beyond the scope of these 

guidelines. Four other important siting issues for SMRS-OG stations are briefly discussed 

below. These topics and discussions are not comprehensive, but are intended to raise 

main issues for further consideration. 

4.5.3.2.1 Background Vibration 

Although not as serious a problem as with high-gain broadband stations, SMRS-OG 

stations should be kept away from potential sources of vibration. These can include: 

• Large motors, pumps, or generators; 

• Large pipelines with active flow; 

• Large masts, poles, or trees; 

• Heavy vehicle traffic; and 

• Industrial activities 

When in doubt, it is suggested that the background vibrations at a potential site be 

monitored. Peak ground vibrations should be less than 0.001g. 

Even if the steady-state background vibrations are small, care must be taken to avoid 

locations where large vibrations could be induced during a strong earthquake. Large 

valves, pumps, or other mechanical or electrical devices that could activate or fail during 

earthquake shaking and transmit abnormal energy pulses also should be avoided. 

4.5.3.2.2 Security 

In both urban and remote areas, vandalism can be a problem for SMRS-OG stations. One 

must make provisions for security in the station design. This can be accomplished using 

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stout enclosures, locks, tamper-proof external hardware, and fenced enclosures. If fencing 

is used, care must be taken to minimize contamination of ground motions by the vibration 

of the fence; lightweight is best. The best security measure is providing a low profile for 

the station. 

4.5.3.2.3 Power 

Modern strong motion instrumentation, especially with real-time digital communications, 

will require a reliable power source of as much as a few tens of watts. For an SMRS-OG 

station, this power issue can provide a significant challenge. Solar power options are 

available, but several large solar panels will be required for most strong motion reference 

stations. This power issue should be carefully considered during planning and design for 

strong motion reference stations on open ground. One must also take care to minimize 

contamination of ground motions with vibrations from large solar panels and their 

supports. In any case, a battery system with enough capacity for 4 to 7 days of operation 

without power is needed. 

4.5.3.2.4 Communications 

The ANSS strong motion reference stations will be connected to some form of digital 

communications for data transfer and maintenance purposes. During the planning phase 

of a new station, one must consider the availability of appropriate communications. It 

may be difficult to connect wire- or fiber-based communications to a self-contained open 

ground station; one can consider wireless options in this case. One must also take care to 

minimize contamination of ground motions with vibrations from large antennae masts 

near the strong motion sensor. 

4.5.3.3 Recommended Station Design 

There are many different strong motion station designs that have been used in both past 

and present. However, note that some of these designs use large foundation blocks or 

piers, which may not be appropriate for the definition of a strong motion reference station 

contained in these guidelines. 

Installation at an open ground location requires constructing a reinforced concrete 

mounting pad with a lightweight enclosure. A small concrete slab/pad and a lightweight 

enclosure will help meet the goal that the transmissibility of the installed strong motion 

station be 1.0 over the frequency range 0.02 – 50 Hz. 

To provide a standardized design for ANSS strong motion reference stations, 

recommended station designs for both self-contained stations (containing all electronics 

within one enclosure) and remote sensor stations (containing only the sensor, other 

electronics remote) are fully described in Document C-USGS-2000-01, Ver. 0.92 

(COSMOS Guidelines for Installation of Advanced National Seismic System Strong 

Motion Reference Stations), pages 13 and 14. 

Other station designs, if used, should be experimentally or analytically studied to verify 

that the completed station does not significantly affect the recorded ground motions. 

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4.5.4 Reference Stations In Small Buildings 

An acceptable strong motion reference station can also be installed within a building 

small enough to have minimal effect upon the earthquake shaking. This section contains 

siting criteria and a discussion of siting issues for strong motion reference stations in 

small buildings. 

4.5.4.1 Siting Criteria 

A strong-motion station will be considered a “Strong-Motion Reference Station: Small 

Building” (SMRS-SB) if it meets all of the following criteria): 

• It is located within a small building (<4000 sq. ft in plan and <2 stories in 

height); 

• It is installed on grade; 

• It is located in a building without significant basement; 

• It is located in a building with a small foundation (flat slab preferred, no pile 

foundations or deep spread footings); 

• It is located in a building of relatively lightweight construction (wood frame 

preferable, but reinforced masonry acceptable); and 

• It is located a distance of at least one major structural dimension (height or 

length, whichever is greater) from any large building (>4000 sq. ft in plan or >2 

stories in height) or any building with a significant basement or foundation; 

• It is located a distance of at least one major structural dimension (height or 

length, whichever is greater) from any non-building structures likely to cause 

significant soil-structure interaction effects that will contaminate the data. 

4.5.4.2 Siting Issues 

Siting issues are generally the same as for SMRS-OG stations with the following 

exceptions. 

4.5.4.2.1 Background Vibration 

Strong motion reference stations in buildings should be kept away from potential sources 

of ground and structural vibration. These can include: 

•Large motors, pumps, or generators; 

•Unsupported floor slabs; 

•Localized human activity; 

•Heavy vehicle traffic outside; and 

•Industrial activities. 

Care should also be taken to protect the sensor from impact of falling objects. It is 

recommended that a clear space of 2m (minimum) be maintained around the sensor, and 

that the general area of the sensor be maintained free of furniture or contents that could 

move during an earthquake and contaminate the measured motions with impact 

vibrations. 

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4.5.4.2.2 Security 

Vandalism can be a problem for strong motion stations in buildings. One must make 

provisions for security in the design of a strong motion station. A dedicated room with a 

locked door is recommended. Some installations also have a steel fence cage around the 

sensor within a non-dedicated room. 

4.5.4.2.3 Power 

For a strong motion station in a building, power may not be a major issue. However, 

sufficient power reserve should be provided in case of power failure, through batteries or 

an UPS, for operation for 4 to 7 days. Power conditioning is also a good idea. 

4.5.4.2.4 Communications 

In a building, communications may not be a major issue as with stations on open land, 

but it is still an important issue to be considered. 

4.5.4.3 Recommended Station Design 

There is no one recommended design provided here for a strong motion reference station 

within a small building, because each building situation will be different. However, 

following are several strongly recommended features of a building installation: 

• The sensor, recorder, and all auxiliary components must be bolted or fastened 

securely to a major part of the structure, preferably the floor slab; 

• The location within a building should be as secluded as possible, away from human 

traffic; 

• The location within a building should be as far as possible from any structural or 

nonstructural building components that may strongly amplify the ground shaking. 

When in doubt, an experienced structural engineer should be consulted for 

appropriate location; and 

• The location should not be in the center of an unsupported floor slab. 

4.5.5 Reference Stations in Densely Urbanized Areas 

Risk to life and property is often greatest in the densely urbanized sections of large 

metropolitan areas such as downtown and high-rise areas of San Francisco, Los Angeles, 

Seattle, and New York. These areas often include older structures built prior to modern 

codes and in many cases may include structures on soft soils near embayment and coastal 

areas. Soil-structure interaction effects of tall structures, bridges, and other transportation 

structures in the downtown areas will likely contaminate ground motions. Seismic 

background noise in these areas will be variable and especially high during rush hours 

and construction periods. Nevertheless, it is these areas for which thorough 

measurements of ground motion and the performance of structures are of highest priority 

and critical for improvements in public earthquake safety. 

4.5.5.1 Siting Criteria 

A strong-motion station will be considered a “Strong-Motion Building Reference Station: 

Densely Urbanized Area” (SMBRS-DU) if it meets the following criteria: 

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• It is located so as to measure representative base floor motions in the densely 

urbanized areas; 

• It is located within a building 10 stories or less in height; 

• It is located on the base floor of the building (i.e. the lowest floor level, whether 

parking or basement). 

Reference stations located in densely urbanized areas should be sited with SMRS-SB 

criteria wherever possible. In those densely urbanized areas for which SMRS-SB type 

sites are not available SMBRS-DU criteria should be used. If possible, the building in 

which an SMBRS-DU station is located should also be instrumented for structural 

response to allow the building response to be removed from the ground or ground floor 

motions. Data from SMBRS-DU stations will be used for comparison with those of 

nearby reference stations located on open ground or in small buildings. 

A suggested goal for a densely urbanized area with high seismic hazard, in which SMRSOG or SMRS-SB stations are not possible, is to have one SMBRS-DU station for every 2 

million square feet of building space or at a density that will ensure documentation of 

rapid changes in underlying geology. Density of stations based on the 2M sq. ft. guideline 

translates into spacing depending on the type of zoning. For zones of dense high-rise 

buildings this may be 1 to 2 square blocks, for zones of low-rise industrial buildings 1 to 

2 square miles, and for urban residential zones several square miles or more. A 

combination of geologic and zoning criteria is required to determine spacing. In densely 

urbanized areas with moderate or low seismic hazard, a rational risk-based approach 

should be considered for optimization of SMBRS-DU station locations. 

4.5.5.2 Siting Issues 

Siting issues are generally the same as for SMRS-SB stations with the following 

exceptions. Note that finding good locations for GPS antennas in downtown areas so that 

signals are not blocked by tall buildings can be an especially challenging problem for 

reference stations. This needs to be considered in the initial site permitting process for the 

instruments. 

4.5.5.2.1 Background Vibration 

Seismic background noise levels will in general be much higher in a densely urbanized 

downtown area than in an area located in a park or away from local cultural noise 

sources. 

When in doubt, it is suggested that the background vibrations at a potential site be 

monitored, so as to locate the instrument in feasible locations within a city block area 

with the smallest levels of peak acceleration during rush hours. 

4.5.5.3 Recommended Station Design 

Recommendations for station design for SMBRS-DU stations are similar to those for 

SMRS-SB stations (previous section). The recommendations are not repeated here. 

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4.5.6 Structural Response Stations 

“Structural Response Stations”, denoted SRS, are ANSS stations designed to measure 

and record the response of civil structures to strong earthquake shaking. Civil structures 

of main interest for ANSS are buildings, bridges, and dams. Other types of structures 

may also be included. The main purpose for these stations is to provide information on 

structural response to earthquake shaking that can be used to improve the safety of design 

and construction practices for new structures, or to assess or reduce the hazards posed by 

existing structures in earthquake-prone regions. For some critical structures, especially 

lifeline structures, SRS information may have more immediate emergency response 

applications such as state-of-health monitoring of structures or generation of regional 

damage indices. 

4.5.6.1 Structural Response Parameters 

The following structural response parameters are of interest: 

• Building translation and rotation in plan 

• Interstory displacements and overall displacement response (including mode 

shapes and periods) 

• Rocking motion (overturning) 

• Floor accelerations and floor load distributions 

• Base input motion 

These data are used to: 

• Evaluate design practices and procedures 

• Determine the severity of damage in a region 

• Assess the health of a structure 

• Identify structural failure mechanisms 

• Assess effects of ground motion characteristics (period, amplitude, duration) on 

structural response 

• Establish threshold levels of damage 

• Verify or identify proposed nonlinear mathematical models of a structure 

• Study soil-structure interaction at the foundation interface 

• Evaluate earthquake rehabilitation methods 

• Assess earthquake hazard potential of existing structures 

4.5.6.2 Siting Criteria 

In general, ANSS SRS should be installed in structures or structure types deemed 

important for either local or national information needs in accordance with ANSS global 

siting priorities. It is recommended that structure selection and structure-specific design 

of an SRS be done by experienced personnel, and that each SRS design be reviewed by 

appropriate ANSS staff or committees. 

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Table 1 – Model Building Classifications Recommended for Instrumentation 

(reference CSMIP 1985) 

Building Type Estimated Prevalence in 

Built Environment 

1. Wood frame (low rise) High 

2. Light metal (low rise) Low 

3. Unreinforced masonry bearing wall (low, 

medium, high rise) High 

4. Frame with unreinforced masonry infill 

(low, medium, high rise) High 

5. Reinforced masonry shear wall with 

moment frame (low, medium, high rise) Low 

6. Reinforced masonry shear wall (low, 

medium, high rise) High 

7. Reinforced concrete shear wall with 

moment frame (low, medium, high rise) Low 

8. Reinforced concrete shear wall (low, 

medium, high rise) High 

9. Steel braced frame (low, medium, high 

rise) High 

10. Steel perimeter moment resisting frame 

(low, medium, high rise) Medium 

11. Steel distributed moment resisting frame 

(low, medium, high rise) Low 

12. Ductile concrete moment resisting frame 

(low, medium, high rise) Low 

13. Nonductile concrete moment resisting 

frame (low, medium, high rise) High 

14. Concrete tilt-up (low rise) High 

15. Precast concrete frame (low, medium, 

high rise) Low 

16. Long span (low rise) High 

17. Base isolated (low, medium rise) Low 

18. Rehabilitated Low 

Following are general criteria to be considered in SRS siting: 

♦ Probability of Shaking: as SRS stations will represent a large investment, they 

should be installed in regions of high probability of shaking. An exception to this 

guideline may be representative unique regional building types in areas of lower 

seismicity. Regions with a seismic hazard greater than 0.1g peak ground 

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acceleration with a 10% chance of exceedance in 20 years shall be considered for 

structural response stations. 

♦ Probability of Learning: SRS stations should be sited to maximize the potential 

of learning in needed areas of earthquake engineering understanding. 

♦ Potential for Loss: SRS stations should be sited in regions with a large 

population or densely built environment that will result in a high potential for 

earthquake loss due to seismic hazard, building inventory, or structure 

vulnerabilities. 

♦ Location Strategy: In general, structures selected for SRS installation should 

logically fit into a regional plan considering both regional and national needs for 

structural performance data. Locations of building structural response stations 

shall be distributed throughout the building inventory such that all model building 

classes are represented and the number of each is consistent with the distribution 

of buildings in the built environment. Model building classifications 

recommended for instrumentation are listed in Table 1. Location of structural 

response stations in non-building structures (dams, lifelines) shall be based on 

regional needs and locally important structures. An exception to this may be the 

desire to instrument important, unique structures for emergency response or 

research purposes. 

♦ Nearby Structures: SRS design shall consider the effect of nearby structures on 

the response of the instrumented structure. Where possible, stations should be 

sited away from structures likely to cause significant soil-structure interaction 

effects that may be recorded in the data. 

♦ Site Conditions: SRS siting should avoid unusual soil or topographic conditions 

which might affect the structural response, unless these unusual conditions are of 

specific interest to ANSS. 

♦ Structural Configuration: In general, buildings selected for SRS installation 

should be regular structures without significant vertical or plan irregularities in 

mass or stiffness, unless these conditions are of specific interest to ANSS. The 

presence of irregularities will complicate the response of the structure and limit 

the usefulness of the data for conclusions regarding general structural response. 

4.5.6.3 Recommended Station Design 

The exact configuration of sensors within an SRS shall be optimized for information 

needs and budgetary constraints. If possible, a pre-analysis of the structure should be 

performed to assist in system design by estimating the global response and identifying 

locations of interest for local structural response. It is recommended that SRS 

configuration design be done by experienced personnel and reviewed by appropriate 

ANSS staff or committees. 

4.5.6.3.1 Configuration 

Following is generic guidance regarding SRS configuration: 

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♦ 

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Ground Motion Reference: A free-field or reference ground motion sensor shall 

be provided near the structure. This shall measure triaxial acceleration. Where 

possible this reference sensor installation shall meet the requirements of 

COSMOS/ANSS SMRS-OG station. 

Structure Base Motion Reference: One triaxial acceleration sensor should also 

be installed at the base of the structure at or below grade to measure “base 

motion.” 

Sensors for Global Response: Sufficient acceleration sensors shall be distributed 

in the structure to resolve linear modal response (frequencies and gross mode 

shapes) based on the global response predicted for the structure. Both translation 

and torsion shall be considered. 

o Global translation: Consider installing single-component sensors at the 

roof and at each intermediate level of low-rise buildings up to three stories 

in height; at the roof and two intermediate levels of mid-rise buildings four 

to seven stories in height; at the roof, two intermediate levels and locations 

of stiffness discontinuities in high-rise buildings more than eight stories in 

height. 

o Global torsion: Consider installing pairs of single-component sensors at 

opposite ends of a floor plate at each instrumented level of a building. 

Differences between these measurements will estimate the torsional 

response. 

Sensors for Local Response: Other sensors shall be distributed as required to 

measure important local responses, such as relative displacements or component 

strains identified as key parameters in a pre-analysis. Sensors for local response 

need not be limited to accelerometers. Use of extensometers, strainmeters, and 

electronic distance measuring technology should be considered. 

4.5.6.3.2 Specifications 

An SRS should be designed and installed to provide appropriate data for understanding 

the response of the structure. General guidance for installation is provided below 

(guidance for acceleration instrumentation is provided in chapter 3): 

♦ Measurement Types: Acceleration and displacement based quantities should be 

the main quantities measured. Sensors other than accelerometers shall be 

considered in SRS design when appropriate. Recording shall be digital. 

♦ Triggering: For triggered recording systems, trigger thresholds shall be 

appropriate for the expected earthquake and structural response motions. Preevent times shall be sufficient to capture the P-wave upon S-wave triggering; 10 

seconds is a recommended minimum. Post-event times should be adequate to 

capture significant free response of the structure after ground shaking has stopped. 

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30 seconds is a recommended minimum, but more will be required for lowfrequency structures such as high-rise buildings or long-span bridges. 

4.5.6.3.3 Installation 

♦ General: SRS instrumentation shall be installed with normal standards of 

professional care. The need for long-term reliability shall be foremost in the 

installation work plan and details. 

♦ Station Location Accuracy: Documented accuracy of one ten-thousandth of a 

degree in latitude and longitude. 

♦ Sensor location accuracy: Within the structure, sensor location accuracy should 

be 1m or better in all three axes relative to a designated reference sensor. 

♦ Sensor Orientation: Sensors within a structure shall be oriented in a logical 

manner, either to compass points or in line with the structure’s primary axes. 

Sensors shall be mounted within 2 degrees of the desired orientation within the 

structure. Sensor orientation is critical to data interpretation and shall be well 

documented and controlled. 

♦ Anchoring: All sensors, recorder and auxiliary components shall be anchored 

securely to the structure to prevent relative motion. 

♦ Site Documentation: An SRS installation should be extensively and formally 

documented, with narrative and photographic descriptions of each component of 

the instrumentation system. This documentation shall also include sufficient site 

condition data for evaluation of local site effects and soil-structure interaction. 

♦ Maintenance Program: A post-installation maintenance program is essential to 

the success of an SRS. 

4.6 References 

COSMOS, 2001, Guidelines for the Installation of Advanced National Seismic System 

Strong Motion Reference Stations, prepared by COSMOS for the USGS, Document CUSGS-2001-01. 

CSMIP, 1985, Recommended Building Strong Motion Instrumentation Criteria for the 

California Strong Motion Instrumentation Program, prepared by the Building 

Instrumentation Subcommittee for the California Seismic Safety Commission. 

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Hanka, 2001, Which Parameters influence the Very Long Period Performance of a 

Seismological Station? Examples from the GEOFON Network, 

http://www.gfz-potsdam.de/geofon/agu_pub/ 

Huang, M., C. Ventura, and A. Shakal, 1989, Strong-Motion Records from Buildings, 

Structures Congress ’89: Seismic Engineering: Research and Practice, American Society 

of Civil Engineers, New York, 1989, v.1, pp. 237-246. 

Holcomb, G., 2002, USGS Open File Report, in preparation. 

Holcomb, G., and Hutt, R., 1992, An evaluation of installation methods for STS-1 

seismometers. Open File Report 92-302, U. S. Geological Survey, Albuquerque, NM. 

Ishihara, K., 1996, Soil Behavior in Earthquake Geotechnics, Oxford Engineering 

Science Series, No. 46, Clarendon Pr., ISBN:0198562241. 

McMillan, J., 2002, Methods of Installing United States National Seismographic Network 

(USNSN) Stations, USGS Open File Report, in preparation, 12 pp. 

Uhrhammer, R. A., W. Karavas, and B. Romanowicz, Broadband Seismic Station 

Installation Guidelines, Seis. Res. Letters, 69, 15-26, 1998. 

http://www.seismo.berkeley.edu/seismo/bdsn/instrumentation/guidelines.html 

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5 Data Archiving and Distribution Subsystem 

5.1 Introduction 

This chapter describes the high level requirements for the Data and Archiving 

Distribution System (DADS), a sub-component of the ANSS. The DADS will rely 

heavily upon the Network Architecture and Interconnection (see Chapter 2) to receive 

and transmit its information, and similarly will be driven by the needs identified by the 

Data Analysis and Products (DAP, Chapter 6) component to determine the types of data 

and information that must be handled. 

This summary is presented at a rather high level. Developing lower level requirements, 

in increasing detail, will be necessary in order to build the complete DADS system. 

At this point, this document does not address any design or implementation issues. For 

example, a requirement for a highly reliable DADS may necessitate a design with a dual 

redundant data center architecture. However, the requirements should specify only the 

target reliability. Only after this requirement is agreed upon can a design consistent with 

meeting the requirement be developed. 

5.2 Operational Concept 

The DADS provides a mechanism for collecting together raw data, derived parameters, 

and metadata produced by the stations and processing centers comprising the ANSS. 

Data are acquired from data concentrators and/or data processing (operation) centers. 

Data may be transmitted to the DADS continuously, in near-real-time, or in batch mode, 

though receiving data via continuous telemetry is strongly preferred. Note that if 

waveforms are telemetered directly to a DADS facility from the field, they will be 

acquired and reformatted as needed by a collocated concentrator. 

Quality control of data is the responsibility of the processing centers, but the DADS will 

have basic QC capabilities where these capabilities make sense, particularly for functions 

that depend on the aggregations of data within the DADS. However, the processing 

centers are solely responsible for producing the definitive version of any data. The DADS 

shall have the capability to synchronize holdings with processing centers and production 

outlets for the purpose of obtaining or maintaining definitive versions of the data. Users 

will thus be able to receive the same version of data, whether they are receiving the data 

from a regional processing center or from the DADS. The DADS must be able to 

properly identify and track data from multiple sources through a data tracking and 

versioning system. 

The DADS distributes the waveforms, all metadata necessary to use the waveforms, and 

derived products in standard formats with the goal of supporting only a single standard 

format for each type of data. Data can be distributed in arbitrary (custom) aggregations, 

and regardless of whether the data are associated to a particular event or are unassociated. 

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Supported data distribution mechanisms shall include continuous near-real time 

transmission, data requests, and data subscriptions (standing orders). 

The DADS archives all data and products indefinitely, and in a manner that provides data 

security and allows continuing operation during regional-scale natural disasters or 

technology infrastructure disruptions. Operational concept highlights include: 

• Receive data (time series and discrete measurements) 

• Receive products derived from data 

• Receive metadata that describe the raw data 

• Archive data, metadata, and products 

• Distribute data, metadata, and products 

• Synchronize holdings with processing centers 

• Define and support a single format for incoming waveform data 

• Define and support a single format for each outgoing data type 

• Perform only limited, non-definitive, quality control (QC) on the data 

• Receive and distribute raw data and data products via multiple data transfer 

mechanisms 

• Be highly available 

5.3 Requirements 

The requirements are categorized in several ways. System level requirements are 

presented first. To the extent possible, these requirements address only capabilities 

required of the overall system, and not specific functional behaviors. The second category 

of requirements are those which apply to interfaces between the DADS and other systems 

or entities. Finally, requirements that address the specific functional behavior of the 

system are presented. 

5.3.1 System Level Requirements 

The DADS is a subsystem of the ANSS, with interfaces to other subsystems, and an 

architecture suitable for fulfilling its requirements. This section addresses those 

requirements that apply to the entire DADS subsystem. Note that these system 

requirements all lead to more detailed interface and functional requirements, but herein 

only the most fundamental requirements of the DADS are characterized: receiving, 

archiving, and distributing data. Although the DADS will be capable of distributing data 

in real time for the general scientific community, the real time needs of the operation 

centers and production outlets will not, in general, rely upon the DADS. 

The Data Archiving and Distribution Subsystem: 

• Shall be capable of receiving all of the types of data collected by the ANSS 

• Time series (waveform) data 

• Discrete measurements 

• Shall be capable of receiving all products derived by the ANSS 

• Shall be capable of receiving all metadata associated with received data 

• Shall be capable of receiving the entire volume of data produced by the ANSS 

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• Shall manage only those data for which complete metadata are also provided 

• Shall archive all data, metadata, and products received 

• Shall be able to distribute, on demand, any of the archived data, metadata, or 

products 

• Be essentially continuously available, with no outages during 

• Natural disasters 

• Regional-scale infrastructure disruptions (power failures, communications 

failures, etc.) 

• Shall satisfy specific availability requirements (which are to be determined) for 

such areas as: 

• Availability of the system for data import 

• Availability of the system for data export 

• Acceptable latencies, which in general will be greater than latencies required 

of the ANSS processing centers 

• Shall provide a high degree of data security 

5.3.2 Interface Requirements 

The DADS must interface with multiple entities, including processing centers and data 

users. The structure of some of the interfaces will be determined by the Network 

Architecture and Integration subsystem. 

The Data Archiving and Distribution Subsystem: 

• Shall receive and transmit data, metadata, and data products from and to 

processing centers with minimal delay introduced at the centers 

• Protocol(s) determined by NAI subsystem 

• Formats determined by the DADS 

• Shall exchange information with processing centers for the purpose of 

synchronizing holdings 

• Shall support a synchronization protocol (a request/response language built on a 

format and an underlying protocol) 

• Protocol(s) and formats determined by DADS 

• Shall provide data (and corresponding metadata) and products in response to 

• Custom requests 

• Subscriptions (standing orders) 

• Shall provide 

• Derived data products 

• Continuous waveform feeds 

• Engineering products 

5.3.3 Functional Requirements 

These requirements attempt to address the specific behavior of the DADS. Note that a 

distinction is made between data formats and data exchange protocols. Requirements 

related to data formats and data exchange protocols will need to be pushed down to much 

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greater detail, and this work must be done in conjunction with the several other 

subsystems that are affected by these formats and protocols. The requirements stated here 

reflect the fact that the DADS needs to be flexible in some ways (e.g. by importing data 

via multiple protocols) and yet rigid in other areas (e.g. controlling the number of formats 

supported). 

5.3.3.1 Data import 

• Multiple data transfer protocols shall be supported for receiving continuous and 

non-continuous (segmented) data from cooperating organizations 

• Acknowledged, point-to-point protocols 

• Ring-buffer-based protocols 

• Client-server push or pull protocols 

• Shall support receiving data via bulk data shipments 

• Electronic transfer (e.g. FTP) 

• Physical media (e.g. tape) 

• A single protocol shall be supported for importing data from processing centers 

and production outlets for the purpose of synchronizing holdings (synchronization 

protocol) 

• Shall support receiving data/metadata/product updates for data previously 

received (versioning) 

• Shall support tracking of the path/mechanism by which data were received 

5.3.3.2 Data export 

• Multiple data transfer mechanisms shall be supported for distributing continuous 

and non-continuous (segmented) waveforms, metadata, and parameters 

• A single protocol shall be supported for exporting data to processing centers for 

the purpose of synchronizing holdings (synchronization protocol) 

• Multiple user data request mechanisms will be supported 

• E-mail 

• Web (GUI) 

• Interactive query results 

• Shall satisfy data distribution timeliness requirements, which are to be determined 

• Timeliness requirements shall be established for: 

• Class of user (e.g. processing center, end user, etc.) 

• Data requested (e.g. data type, data age, volume of data, etc.) 

5.3.3.3 Formats 

• Data received from processing centers or data concentrators shall be in a single 

standard format 

• No format conversion is required for these data 

• Will maintain ability to re-construct raw data, by either: 

• Preserving raw, unconverted, data 

• Preserving descriptive information about raw data (e.g. original segment 

boundaries, etc.) 

• A single standard format is supported for data archiving 

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• Legacy data are archived via encapsulation in (or translation to) the standard 

archiving format 

• A single standard format is supported for data distribution 

• Format shall include both data and corresponding metadata 

• Mechanisms to distribute waveform data alone and/or metadata alone will also be 

provided but will be closely tied to the standard format 

• Software for converting the standard format into widely used community 

consensus formats will be provided. 

5.3.3.4 Synchronization 

• Shall support specific rules for updating holdings 

• Shall have the capability to initiate a synchronization request 

• Shall have the capability to receive a synchronization request 

• A synchronization request may serve to: 

• Push updated data to another site 

• Pull updated data from another site 

• Seek data to fill gaps in holdings 

• Verify the version or accuracy of data in a site’s holdings 

• Shall have the capability to receive or transmit data to achieve synchronization 

with a processing center 

• Shall have the capability to update the archive when updated (replacement) data 

are received 

5.3.3.5 Archiving 

• Shall have the capability to archive all data types collected by the ANSS 

• Includes time-series data of any sample rate 

• Includes discrete observations 

• Specific data products to be archived will be determined by Data Products 

committee 

• Shall have the capability to archive all processed (including QC'ed) time series 

data produced by the ANSS 

• Shall archive all metadata associated with archived data 

• Shall have the capability to archive all processing results (parametric information) 

produced by the ANSS 

• Specific data products to be archived determined by Data Products committee 

• Archive both the raw or equivalent and processed time series data. 

• Shall archive all data, metadata, and products such that queries to a DBMS may 

exploit relationships between these classes of information 

• Note: this does not imply that waveforms must be stored directly within a 

DBMS 

• Shall archive data indefinitely 

• Shall maintain a data management policy, reviewed annually, that addresses 

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• Data storage migration to avoid extinction of formats/and storage media as 

well as the storage device technology 

• Data security (loss prevention) 

5.3.3.6 Quality control 

• Primary data quality control shall be performed by the operation centers and 

production outlets 

• The DADS shall have the capability to perform limited quality control 

• To verify the integrity of holdings 

• Where such quality control can only reasonably be performed on aggregations 

of data only present within the DADS 

• Certain routine assessments of data quality such as signal to noise ratios, 

power spectral density functions, and other automatic quality control 

procedures 

5.4 Other Issues 

The architecture of the DADS has been extensively discussed in the DADS meetings, but 

no final recommendations are included herein. Instead, one or more working groups will 

develop the DADS and address these issues: 

• A centralized rather than distributed architecture (i.e., a centralized archive). 

• Redundant archives to promote high availability. 

• Off-site storage for data security. 

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6 Data Analysis and Products 

6.1 Introduction 

The ANSS must provide a timely, standardized, coordinated, automatic supply of 

authoritative earthquake data and products. The data collected, products generated, and 

the methods used to generate products need to be clear and fully documented in order for 

interested parties to use them confidently. The ANSS must provide robust, timely, 

interactive distribution of data and products system-wide and provide assistance with 

understanding the data and products to those who need it. 

The ANSS must distribute earthquake data and products to a wide variety of users over a 

broad range of time scales. In particular, regional and national processing centers and 

production outlets have the responsibility to provide rapid earthquake information to 

time-critical users, while the archiving facilities distribute data and information to nontime-critical users. 

6.2 Users 

The logical flow of data is from field instrumentation to processing, distributing, and 

archiving of data and information products. At each step, user requirements should 

govern the system design and performance. This section identifies several categories of 

anticipated ANSS users, briefly summarizes their primary activities, and describes their 

needs for seismological data and products. 

6.2.1 Earthquake Emergency Responder 

Primary activities: 

• Identify areas and levels of damage 

• Assess level of damage/functionality at specific buildings or facilities 

• Understand related phenomena such as tsunami, landslide or volcanic activity 

Data and information needs: 

• Fair-quality digital data from densely instrumented urban areas 

• Good-quality digital building data from special-interest buildings 

• Near real-time processed data and derivative products 

• Access to expert knowledge and training regarding data and products 

6.2.2 Media, Public Officials, K-20 Educators, and the General Public 

Primary activities: 

• Be informed about what is happening 

• Make better risk management decisions at public and personal levels 

Data and information needs: 

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• Raise earthquake hazard awareness and understanding of the earth 

• Near real-time derivative products that are easy to understand and reliably 

delivered to large numbers of recipients 

• Interpretation provided by local experts 

6.2.3 Earthquake Engineer 

Primary activities: 

• Evaluate building performance as a function of reference ground motion 

• Update structural seismic design requirements based on strong motion recordings, 

processed data, and damage correlation studies 

• Advise building owners/occupants about safety and functionality of instrumented 

buildings 

Data and information needs: 

• Unclipped strong motion waveforms from 3-component reference stations and 

instrumented buildings and other structures 

• Near real-time and archived processed strong motion data 

• Detailed information about site conditions, sensor locations, and building design 

• Structural state-of-health monitoring reports 

• Measurements of global and local structural deformation 

6.2.4 Seismic Hazard Analyst 

Primary activities: 

• Characterize seismic sources by style of faulting, depth of faulting, stress drop 

• Use earthquake catalogs to assess recurrence 

• Estimate seismic hazards 

Data and information needs: 

• Uniformly processed catalogs of earthquake source parameters including 

magnitude, depth, focal mechanism, stress-drop, and fault association 

• Identification of aftershocks 

• Attenuation and site response information 

6.2.5 Engineering Seismologist and Geotechnical Engineer 

Primary activities: 

• Determine attenuation of ground shaking with distance and source characteristics 

• Evaluate site response as a function of source characteristics and site geology 

Data and information needs: 

• Good-quality digital data from dense arrays near causative fault 

• Data from a wide range of site conditions 

• Unclipped waveforms from 3-component strong motion reference stations 

• Real-time and archived data, both unprocessed and processed 

• Detailed geotechnical site characterization of all instrumented sites 

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6.2.6 Regional Seismologist 

Primary activities: 

• Study regional earthquakes, determine source parameters and characteristics 

• Study regional crust and mantle structure and properties 

• Associate earthquakes with faults and tectonic features 

• Study earthquake source processes 

• Provide earthquake information to all interested parties in near real-time 

Data and information needs: 

• High-quality, 3-component, high dynamic range broad-band digital data on 

regional and local scales 

• Real-time and archived raw and derived data 

6.2.7 Global Seismologist 

Primary activities: 

• Study the locations, source parameters, and characteristics of worldwide 

earthquakes 

• Provide earthquake information to all interested parties in near real-time 

• Study large-scale earth structure and properties 

• Study earthquake source processes 

Data and information needs: 

• High-quality, 3-component, high dynamic range broadband digital data on global 

and continental scales 

• Real-time and archived raw and derived data 

6.3 Rapid Products 

When an earthquake of potential general interest occurs, the ANSS should routinely 

provide: 

• Real-time seismograms - Media, technical staff, researchers, and public like access to 

real-time visual seismograms. 

• Phase picks - Currently single component phase picks are common. Recently three 

component picks have been developed. 

• Origin time - Time should be available in UTC format and local time formats. 

• Hypocenter – Locations should be available in both degrees-minutes and decimal 

degrees format. Depth should be available. Quality information such as error 

estimates, number of phases used, and distribution of stations should be available. 

• Distance from reports - Distances from cities (small, medium, and large), quarries, 

faults, and historical large events. Distances from seismic stations are often 

requested. 

• Magnitudes - A wide variety of magnitudes should be available including mb, and 

Ms, Mcd, Ml, Me, Mw. Quality information should be available such as number of 

stations, and components used in solution. 

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• A single representative, authoritative magnitude should be chosen for distribution 

to the public and press 

• Earthquake reports – Easily understandable event summaries distributed in many 

ways including emails and pages. 

• Ground Motion Amplitudes – A wide variety of ground motion types including 

acceleration, velocity, displacement, spectral acceleration and velocity, and energy. 

• ShakeMaps – Graphical representation of shaking information is rapidly becoming 

essential information. 

• Event review pages – Rapid evaluation of automatic solutions supported by specially 

designed review pages that show waveforms, automatic phase picks and other 

information (for use by skilled staff only) 

• Moment tensors and focal mechanisms – A variety of techniques should be 

supported. 

• Structural state-of-health monitoring reports – the ability to assess the condition of an 

inventory of structures in an automated way would be useful in emergency response 

scenarios. 

• Measurements of global and local structural deformations – direct measurement of 

structural displacements will help in post earthquake assessment of structures, and in 

future engineering research. 

6.4 Information Products 

Information will be provided by the ANSS on a regular schedule for each region and for 

the nation as a whole. These should include but are not limited to the following: 

• Intensities listed by city or landmark – Intensity reports on a city-by-city basis may 

provide more useful information to the public than magnitude reports. 

• Community intensity map – The public contributes to produce an intensity map based 

on public reports. 

• Maps – Printed and Web based maps showing recent events in a geographical area are 

popular and important. 

• Catalog of quakes – Some users continue to favor text based earthquake catalog 

formats. 

• Operation reports – summaries of station installations, problems and changes and 

other operational events. 

• Event and continuous waveform data - The seismological research community will 

look to the ANSS to provide continuous waveform data for studies in earthquake and 

volcano processes and Earth structure. This will require both archives of continuous 

waveforms and event-based waveforms. 

• Derived time series – The engineering community is vitally interested in both raw 

time series as well as in derived time series (acceleration, velocity and displacement). 

Details about the processing steps used to obtain the product are essential to its use. 

• Spectral data series – The engineering community also wants response spectra, 

distributed in standard formats with documentation of damping values, periods, and 

the computational algorithm used. 

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• Station metadata - Station coordinates, DAS and sensor type, instrument response. 

For strong-motion data, additional information about the near-surface geology and 

shear wave velocity is needed. 

The ANSS will provide specialized reports on subsets of all data - at all stages. For 

example, it is increasingly common to request a subset of all the data available, and then 

to perform additional processing using just this data subset. For example, partners may 

be interested in information from ANSS stations collocated at their facilities. The ANSS 

will support this type of data report. 

6.5 Interpretation 

The routine operation of the ANSS will provide many standardized products, mostly in 

computer generated and readable forms. These will be distributed to a wide variety of 

users, many of who lack sufficient experience or training to use or even fully understand 

these products. The ANSS must provide functionality to assist many users with the 

interpretation and understanding of the routine products. Examples of these functions or 

personnel are the following: 

• Public/press – interface with the general public and news media. 

• Policy issues – interface with government and civil authorities regarding hazard 

mitigation or emergency preparedness. 

• Science – interface with other seismologists, geologists, engineers about specifics 

of the data and products 

• Data access – Database access issues for special requests. 

The personnel involved in the interpretation of the ANSS routine data and products can 

contribute greatly to the development and evolution of new procedures and products. 

Feedback from the users will play an important role in maintaining high quality and 

relevant products. 

6.6 Authority 

The distributed ANSS system will be capable of providing authoritative earthquake 

parameters and rapid response data and products at all times. At a minimum, the ANSS 

will have a national production outlet that is staffed 24 hours a day, seven days a week. 

The ANSS will provide continuous system monitoring, system control, and authoritative 

earthquake parameter and rapid response information. The ANSS will operate under 

“incident command and response rules” that provide clear guidelines as to who is in 

charge. The national production outlet will serve as an arbiter among the regions in 

resolving divergent views of the same earthquake. Appropriate business rules and 

mechanisms will ensure that a single authoritative set of parameters is available for each 

event at any time. The ANSS archive system will synchronize data with processing 

centers to ensure that data holdings are complete and current. The national production 

outlet will have the responsibility to construct a comprehensive seismicity catalog that is 

a superset of the regional and global events. Regional production outlets will have ‘on 

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call’ staff available to respond rapidly to significant earthquakes in their region and to 

review routine data and products with the national production center. 

6.7 Data Processing 

The ANSS should be responsible for providing uniform software and technical support 

for all centers and outlets (national and/or regional) producing ANSS standard products. 

Data shall be processed in accordance with the time-critical nature of their intended use. 

Table 2. Data Processing 

Product Latency range Comments 

Early Warning 0-90 sec Used for life safety actions and rapid 

mitigation 

Preliminary automatic 

hypocenter 

30 sec The automatic determination of the 

hypocenter will depend on the location of 

the earthquake with respect to the network. 

Shorter time frames will be available in 

areas with denser instrumentation 

Updated automatic 

hypocenter; 

Preliminary automatic 

magnitude 

60 sec - 120 

sec 

Updated estimates of the hypocenter should 

be issued within 1-2 minutes. An automatic 

estimate of the magnitude should be 

available on the same time scale. 

Preliminary automatic 

ground shaking maps 

3 - 5 min Preliminary maps of strong ground shaking 

should be issued within a few minutes 

following a qualifying event. As with 

hypocenters, this will depend somewhat on 

the distribution of stations. Depending on 

the location of the event, some maps may 

depend more on predicted motions than on 

observed data. 

Updated automatic 

magnitude; 

Preliminary automatic 

seismic moment tensor 

5 - 6 min Updated automatic magnitude estimates will 

be issued for some events as more stations 

become available or as additional 

processing is completed. 

Rapid review 5 - 10 min after 

notification 

Alarm events will require rapid review 

within a few minutes after notification. 

Mapped PGA and 

Intensity 

(ShakeMap) 

5 - 15 min Used for situation assessment, estimation of 

disaster scope, determination of 

mobilization level, focused reconnaissance, 

mutual aid activation, and staging areas 

Revised review within 72 hrs Updated information and recovery estimates 

The numbers in this Table are applicable to normal system operation. If a component 

fails (say, if one of the regional processing centers is crippled), then the latencies are 

naturally longer to allow for the propagation of seismic waves to more distant stations. 

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7 Appendices 

Appendix A – TIC and Subcommittee Members 

Jon Heintz, Chair 

jheintz@degenkolb.com 

Kaye Shedlock, Vice-Chair 

shedlock@usgs.gov 

Tim Ahern 

tim@iris.washington.edu 

Ray Buland 

buland@usgs.gov 

Steve Malone 

steve@geophys.washington.edu 

Woody Savage 

wusavage@usgs.gov 

Degenkolb and Associates, Inc. 

U.S. Geological Survey 

Incorporated Research Institutions for 

Seismology 

U.S. Geological Survey 

University of Washington 

U.S. Geological Survey 

Subcommittee on Data Analysis and Products 

Terry Wallace, UAZ, (Chair) 

Lucy Jones, USGS 

Farzad Naeim, John A. Martin & Associates 

Gary Patterson, CERI/UM 

Ken Parrish, WA State Emergency Management 

Subcommittee on Data Archiving and Distribution 

Ralph Archuleta, UCSB (Chair, Emeritus) 

Bob Woodward, SAIC (Chair) 

Rick Benson, IRIS 

Harold Bolton, USGS/ASL 

Ahmed Elgamal, UCSD 

Katrin Hafner, Caltech 

Bob Herrmann, SLU 

Doug Neuhauser, UCB 

Melinda Squibb, UCSB 

Subcommittee on Instrumentation 

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Tom McEvilly, UC Berkeley (Chair, Emeritus) 

Bob Hutt, USGS/ASL (Chair) 

Norm Abrahamson, PG&E 

Joe Savage, USACE 

Frank Vernon, UCSD 

Subcommittee on Network Architecture and Interconnection 

Lind Gee, UCB (Chair) 

Doug Given, USGS 

Stephen Goldstein, NSF 

Kent Lindquist, UAK 

Gary Pavlis, IU 

Tony Shakal, CDMG 

Mitch Withers, CERI 

Subcommittee on Site Installation 

Bob Nigbor, USC (Chair) 

Jon Berger, UCSD 

Moh Huang, CSMIP 

Doug Johnson, LDEO 

Tom Shantz, CA DoT 

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Appendix B – Data Rate and Volume Estimates 

Below is a summary table of a data flow model prepared by the TIC for the ANSS. The 

model starts with a description of network elements or data sources including the number 

of stations per element, the number of components, sample rate, and field triggering 

percentage for both seismometers and accelerometers at each station, and the average 

number of bits per sample. The bits per sample represent the mean output of a 

compression algorithm (including compression overhead). 

Given this information, telemetry data rates, intermediate data buffer volumes, and 

archival volumes are estimated. Data rates include 20% telemetry overhead (data record 

and protocol packet headers, etc.). Intermediate data buffer storage is needed at the 

production outlets to support rapid review of automatic products, at the processing 

centers to support network triggering of continuous data, and at data concentrators and 

processing centers to provide complete data through telemetry outages (to other centers). 

Archive volume calculations provide for the possibility of a different compression 

amount and for discarding additional data at the operation centers (after telemetry from 

the field). Derived products and station metadata have not been included in the exchange 

rates because they are negligible. Products and metadata have been included in the 

archive totals as an overhead. Note that the data exchange rate would also apply to data 

exchanges between operation centers. 

The TIC recommends that national backbone broadband, regional broadband, urban 

reference, and urban free field data will all be telemetered from the field continuously in 

real-time. Low gain channels from national backbone and regional stations should be 

triggered. 1 Hz long period channels will be generated from the broadband data for both 

national backbone and regional broadband stations (note that this has been represented in 

the spreadsheet by making the sample rates slightly higher). Structural arrays should be 

event triggered, but the telemetry will be continuously available and capable of 

transmitting all data in real time. Note that rather than showing structural arrays as 3000, 

3 component stations, they have been shown as 375, 24-channel arrays. Also note that 

150 Hz sampling provides the full engineering bandwidth using brick-wall FIR filters. 

All data should be compressed in the field. 

At the operation center(s), all data will be acquired and buffered. Reference and free 

field data will be network triggered from this buffer. Data exchanged among regional 

processing centers and transmitted to the national processing and archiving centers will 

include only the event triggered reference and free field data. All data and products will 

be forwarded to the archive facilities as soon as they are available and will be provided to 

the community indefinitely. Note that the waveform data will be archived in compressed 

form. 

Acquisition, processing, and archiving of continuous broadband data from national and 

regional stations seems to have wide community support. Given the availability of 

continuous broadband data, there seemed no compelling reason to telemeter collocated 

low gain channels continuously as well. The choice to telemeter urban reference and free 

field data continuously is less clear. However, it was felt that the ability to extract small 

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events from the data would be better supported at the operation center(s) (using network 

triggers) than in the field. The choice to provide continuously available, full rate 

telemetry for structural monitoring was motivated by the desire to certify critical 

structures as safe or unsafe within 10-20 minutes of an event. Given that only short 

triggers from strong events are of interest, the telemetry data rate could probably be 

safely reduced to as little as 10% of the full data rate. The choice to use compression 

from the field was motivated by the high data rates and experience indicating that 

compression is an effective way of reducing bandwidth requirements provided that 

adequate excess bandwidth is available during events. 

The aggregate telemetry data rate (received) would be spread out over the regional and 

national operation centers. Data rates from individual stations are shown in the second 

able. Note that the telemetry data rate doesn't include stations that are transmitted to 

multiple operation centers from the field. The aggregate data exchange rate is the same 

as the aggregate telemetry rate except that the urban reference and free field data has now 

been triggered as well. This would represent the aggregate data flow into the archive 

facilities and, perhaps, into the national processing center. The exchange data rate also 

provides a rough estimate of the data exchanges among regional processing centers (e.g., 

nearest neighbors exchanging subsets of waveform data). 

Compression Tutorial 

For those not familiar with seismic compression techniques, our ability to compress data 

depends on two factors: 1) about 95% of all seismic data is background noise and 2) most 

of the available dynamic range is rarely used. That is, only a small part of the available 

waveform data contains seismic events and large seismic events are very rare. The 

crudest seismic compression technique is to simply discard noise and keep events. Such 

"triggering" algorithms are generally effective, but typically have 100% false alarm rates 

and may still miss small events. 

The second class of seismic compression algorithms is loss-less. In these methods, all 

data samples are retained, but unused dynamic range (i.e., the high order zeros in each 

sample) is discarded. Differencing or even double differencing the data can enhance this 

process. Note that additional information (overhead) must be embedded into the 

compressed data to allow its recovery. At a quiet site, loss-less algorithms can typically 

compress data from more than 24 bits to less than 6 including overhead. 

The disadvantage of loss-less compression is that the data volume expands during events 

when the compression becomes less effective. The differencing which is also less 

effective when compressing frequencies near the Nyquist emphasizes this effect. 

Theoretically, under worst case conditions, compression could actually lead to more bits 

per sample than uncompressed data. In practice, the correlation of data samples due to 

the anti-aliasing filters precludes this scenario. Experience has shown that allowing 

about 50% excess bandwidth is adequate to ensure real-time telemetry essentially all the 

time. Additionally, because of the attenuation of the earth, periods of degraded 

compression efficiency are typically short compared with the earthquake wave train. 

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Table 1 

ANSS Data Rate/Volume Estimates 

Stations Telemetry 

High Gain Low Gain Sample Data Rate per 

Data Source No. No. Rate Trig No. Rate Trig Size Station Source 

Stations Comp (Hz) % Comp (Hz) % (Bits) (Kbps) (Mbps) 

National Backbone 100 3 51 100 3 50 10 8 1.61 0.16 

Regional 1000 3 101 100 3 100 10 8 3.20 3.20 

Urban Ref + Free 3000 3 150 100 8 4.32 12.96 

Urban Structure 375 24 150 2 8 0.69 0.26 

Totals: 4475 3300 21300 16.58 

Buffering Archiving 

Save Data Trigger Sample Exchange Archive 

Data Source for Volume HG LG Size Rate Volume 

(Days) (GB) % % (Bits) (Mbps) (TB/yr) 

National Backbone 7 10.161 100 100 8 0.16 0.56 

Regional 7 201.4 100 100 8 3.20 11.03 

Urban Ref + Free 7 816.48 10 8 1.30 4.47 

Urban Structure 7 16.33 100 8 0.26 0.89 

Totals: 1044.4 4.91 16.96 

Total number of channels: 27900 

Table 2 

ANSS Data Rate Per Station 

High Gain Low Gain Sample Telemetry Data Rates 

Data Source No. Rate Trig No. Rate Trig Size Average Worst Case NRT Trigs 

Comp (Hz) % Comp (Hz) % (Bits) (Kbps) (Kbps) (Kbps) 

National Backbone 3 50 100 3 50 10 8 1.58 2.38 

Regional 3 100 100 3 100 10 8 3.17 4.75 

Urban Ref + Free 3 150 100 8 4.32 6.48 

Urban Structure 8 150 100 8 11.52 17.28 1.73 

" 16 150 100 8 23.04 34.56 3.46 

" 24 150 100 8 34.56 51.84 5.18 

" 32 150 100 8 46.08 69.12 6.91 

1. Worst case rates include excess bandwidth for degraded compression during events. 

2. Near-real-time (NRT) triggers shows data rates to transmit data in 1/10 real-time (a 30 s trigger 

could be transmitted every 5 minutes). 

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Appendix C – Instrumentation Testing 

The following provides details of standards referred to in chapter 3. 

Dynamic Range 

The dynamic range of seismic sensors is to be computed according to the 

recommendations of the Standards for Seismometer Testing Workshop, July 1989. That 

is, dynamic range as a function of frequency shall be defined to be the ratio in decibels of 

the RMS clip level and the RMS noise floor as a function of frequency. The RMS clip 

level shall be taken to be the RMS value of a sine wave of the appropriate frequency that 

just clips. The noise floor shall be taken to be the non-coherent noise between two 

identical sensors recorded at a quiet site (or just the sensor noise if it is well above 

ambient earth noise). The RMS noise floor is computed by averaging power over half 

octave bands centered on the desired frequency, multiplying by the half octave bandwidth 

(to make the units power rather than power/Hz), and taking the square root. 

Vendors are required to provide a plot of the RMS noise floor in decibels (referenced to 

the RMS clip level) versus log frequency including at least the frequency band .01 < f < 

50 Hz for each component of each sensor proposed. For reference, each plot shall 

include the USGS New Low Noise Model (NLNM) and representative earthquake RMS 

spectra (including a model 2.5 Mw event at 10 and 100 km) averaged over half octave 

bands. Note that the NLNM and model event spectra will be provided by the ANSS. 

Resolution 

The resolution of digitizers is to be computed according to the Modified Noise Power 

Ratio test as described in Sandia National Laboratories technical report SAND 94-0221, 

“Modified Noise Power Ratio Testing of High Resolution Digitizers”, by T. S. 

McDonald, 1994. The test involves driving two identical digitizer channels with pseudo 

random, band limited, Gaussian noise and measuring the noise power ratio (NPR), 

defined as the ratio of the RMS input noise to the RMS non-coherent noise floor (both 

averaged over the digitizer pass band). The resolution is estimated indirectly by 

comparing the NPR as a function of RMS input noise against ideal digitizers. Copies of 

SAND 94-0221 will be provided by the ANSS. 

Vendors are required to provide a plot of NPR in decibels versus loading factor in 

decibels compared with theoretical curves for ideal digitizers of varying dynamic ranges 

(i.e., number of bits). The loading factor is the ratio of the digitizer clip level to the RMS 

input noise. The NPR must be determined at RMS input levels between the RMS shorted 

input and clipping in 10 dB steps. Vendors are also required to provide a plot of shorted 

input power in decibels versus frequency and at least one plot of the phase of the noncoherent noise in degrees versus frequency. Both plots must including at least the 

frequency band 0 < f < 50 Hz. 

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Magnetic Fields 

When equipment is operated in the presence of magnetic field intensity changes of up to 

10 milligauss, there shall be no detectable effect in the output signal. 

Atmospheric Pressure 

Sensitivity to atmospheric pressure changes shall not be detectable at the output of the 

instrument including changes due to passing fronts and thunderstorms. 

Radio Frequency Interference (RFI) 

When equipment is operated in the presence of RFI there shall be no detectable effect in 

the output signal provided that the RFI does not exceed FCC standards. For relevant 

standards see “Limits for General Population/Uncontrolled Exposure” (FCC document 

“A Local Government Official’s Guide to Transmitting Antenna RF Emission Safety: 

Rules, Procedures, and Practical Guidance”, June 2, 2000). 

Mean Time Between Failures (MBTF) 

MTBF shall be estimated by the Bell Communications Research (Belcore) method. The 

method is defined in "Reliability Prediction Procedure for Electronic Equipment" 

(Belcore document number TR-332, Issue 6) and may be computed using commercially 

available software (e.g., RelCalc). 

Configuration Information 

Sensors and power equipment shall be capable of reporting and DASes of receiving 

manufacturer, model, serial numbers, and other relevant information as specified (e.g., 

nominal response information for sensors and power status information for power 

systems). Data shall be communicated in the ASCII character code via a 1-wire network 

(MicroLAN) as described in http://www.maxim-ic.com/1st_pages/tb1.htm. 

Temporary Shallow Submersion in Water 

The International Electrotechnical Commission (IEC) standard 60529 specifies degrees 

of protection provided by enclosures, also known as the IP code. ANSS requires IP67 

level protection, which means 1) the enclosure shall be dust tight and 2) the ingress of 

water shall not be sufficient to damage the electronics when submerged under 1 m of 

water (measured from the base) for 30 minutes. 

Appendix D − Production, Interpretation, and Outlets 

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The Advanced National Seismic System (ANSS) real-time and off-line processing 

systems should be constructed from four modular hardware/software building blocks. In 

particular, the heterogeneity and number of the three types of modules (data 

concentrators, operation centers, and data archiving facilities) that are between the 

sensors and the users should be kept to a minimum for reliability and cost reasons. 

However, the fourth module type (outlets, which directly support ANSS participants and 

end users as well as some production tasks) should be diverse and numerous, involving 

the whole community and supporting the whole spectrum of ANSS related uses. 

Production functions (including those performed at outlets) should be logically separate 

from interpretation functions (also performed at outlets). Separating production and 

interpretation allows a system design that supports the goals of a highly reliable 

production environment and a highly diverse interpretation environment. Specialization 

does have negative aspects including problems in communication and coordination 

among groups of specialists. However, other large-scale organizations have developed 

effective strategies for dealing with these issues. While some of these problems have 

already been addressed by the ANSS management structure, others must be addressed as 

the ANSS develops. 

Introduction 

This Technical Guidelines for the Implementation of the Advanced National Seismic 

System, Version 1.0 (hereafter, Technical Guidelines) presents a blueprint for the next 

generation technological infrastructure for fixed network seismology in the US. While 

most of the technical discussion has found wide acceptance within the community, the 

non-technical proposal of a formal separation of production and interpretation functions 

has proven to be more controversial. In the body of the Technical Guidelines, the 

operation center technical construct is associated with production and the outlet technical 

construct with interpretation (but also some production). It seems likely that the 

multiplicity of roles envisioned for outlets has further confused these issues. 

The concern expressed by the seismological community is natural considering that the 

separation of production and interpretation suggests the dismantling of highly successful 

procedures and strategies evolved by Regional Seismograph Network (RSN) operators 

over decades. Inevitably, the scope of the proposed organizational shift has also created 

concerns at many seismological institutions about their future role within the emerging 

ANSS structure. 

In the following, ANSS tasks and their identification with ANSS technical constructs will 

be examined. In particular, the dual nature of outlets will be explored. With a common 

nomenclature established, the recommendation to separate production and interpretation 

will be examined. Finally, the consequences of modularizing ANSS tasks in general and 

separating production and interpretation in particular will be explored. 

ANSS Structure 

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The ANSS organizational structure favors the modularization of various production and 

interpretation functions. Production is identified with both the automated collection and 

processing of seismic waveforms and the routine manual activities that comprise seismic 

practice. In this context seismic practice includes quality control (QC) activities and the 

construction of derivative products such as catalogs. QC includes the review, rapid and 

otherwise, of automated products as well as removing artifacts from waveforms (e.g., 

timing problems) and monitoring the state-of-health of field and processing equipment. 

Each of these tasks may be accomplished by one or more cooperating organizations. 

Similarly, interpretation is identified with non-routine activities that require specialized 

knowledge, insight, and creativity. Thus, interpretation includes interpreting data for 

emergency managers and the media, the development of new algorithms for routine 

analysis and research work, seismological research, and engineering studies. Again, each 

of these tasks may be accomplished by one or more cooperating organizations. For 

clarity, the output of production functions (e.g., waveforms, automated products, 

routinely produced manual products, etc.) is referred to as data. Conversely, 

interpretation organizations can be thought of as consuming data and producing 

information. 

The Technical Guidelines recommends a modular technical structure comprised of data 

concentrators, operation centers, data archiving facilities, and outlets. This structure is 

hierarchical in the sense that waveform data is generated by widely distributed field 

equipment. It is then concentrated onto communication backbones by data concentrators, 

delivered to operation centers where automated products are derived, and finally 

delivered to data archiving facilities where it is organized and stored to satisfy future 

requests. Field equipment, data concentrators, operation centers, and data archiving 

facilities are all automated and performing tasks of a routine nature and therefore are all 

part of ANSS production. 

In addition, data flows in real-time from operation centers and archiving facilities to 

outlets where humans become involved for the first time. Technically, an outlet is 

defined by the machinery needed to ensure the reliable delivery of data pushed from one 

or more operation centers and/or archiving facilities and to organize the data for a variety 

of non-real-time (although perhaps time critical) uses. Organizationally, an outlet is any 

group of people with a standing request for data from one or more operation centers 

and/or archiving facilities. 

The outlet formalism turns out to be a convenient way of implementing a wide variety of 

ANSS tasks fulfilling both production and interpretation functions. For example, the 

rapid review of automated products, waveform QC, and the construction of catalogs are 

all production functions that would be performed at outlets. Similarly, the interpretation 

of data for emergency managers and the media, developing new products and/or 

algorithms, and research are all interpretation functions that also would be preformed at 

outlets. 

Development of the Guidelines 

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The controversy over the proposed separation of production and interpretation raises the 

question of why the Technical Guidelines addresses this fundamentally non-technical 

issue. After all, the Technical Guidelines excludes other non-technical issues such as the 

structure of the field deployment and maintenance effort, the organization of education 

and outreach, and institutionalizing (human) feed back mechanisms among disparate 

elements of the ANSS. The answer, of course, is that the technical and organizational 

structures of the ANSS are inextricably intertwined. In particular, it has proven very 

difficult to visualize whether technical elements of a nationally coherent ANSS are 

workable without some organizational context. 

The same considerations were applied to developing the organizational framework and 

the technical structure. That is, a conscious effort was made to be forward looking and to 

take advantage of past experience without being unduly constrained by current 

implementations. The impact on the whole system of each organizational and technical 

module was considered in the light of ability to meet ANSS goals and to satisfy the needs 

of ANSS funding sources, participants, and end users. 

The idea of separating functions that have traditionally been closely coupled arose from 

several different lines of reasoning. In the following the requirements for production and 

interpretation facilities and the needs of production and interpretation personnel are 

considered. These considerations lead to the conclusion that the production environment 

should be centralized and standardized while the interpretation environment should 

distributed and heterogeneous. 

Production and Interpretation 

Automated elements of the ANSS production environment such as data concentrators, 

operation centers, and data archiving facilities are in the primary path from field 

equipment to users and must be highly reliable to avoid the loss of waveforms and 

automated products vital to effective rapid response. In contrast, outlets are at the end of 

the data path and though they are also essential to meeting the goals of the ANSS, the 

failure of an outlet will not compromise the timeliness or completeness of automated 

products. Of course, the loss of an outlet involved in rapid review or rapid response 

would affect the early confirmation or interpretation of automatic results. However, 

outlets involved in other areas of production and interpretation are not essentially realtime operations and although they need to be reliable, they can tolerate some down time. 

This analysis suggests a hierarchy. The more tightly a task is coupled to real-time, the 

higher the risk of losing data, and the less outages of any length can be tolerated. It is 

easy to show that redundancy reduces the probability a total system failure, but enhances 

the probability of a partial failure due to increased complexity. That is, critical facilities 

should be centralized, but not too much. Therefore, the best balance between redundancy 

and complexity favors a small number of operation centers/archiving facilities and rapid 

review/response outlets, but doesn’t rule out making other types of outlets more 

distributed. 

A reasonable degree of centralization coupled with standardized software make it easier 

to produce standardized automated products, coordinate the release of products among 

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centers, and reduce capital, developmental, operational, and maintenance costs. 

Reducing the cost of expensive support professionals (including seismic analysts working 

24-hour shifts, system engineers, and data base administrators) is critical to the long term 

health of the ANSS. Although standardization tends to stifle innovation, experience 

indicates that support personnel generally work more effectively in a relatively stable 

environment. These arguments also favor centralizing and standardizing production 

facilities. 

The problem with centralization is that it excludes the participation of people who don’t 

work at the centers. This is unacceptable if the ANSS is to meet the goal of providing 

effective local interpretation of earthquake data for emergency managers and the press. 

Also, fostering innovation is important not only in ANSS related research, but also in 

developing new products and algorithms to keep the ANSS current and relevant. 

Innovation requires a heterogeneous, dynamic environment in order to experiment with 

new technologies. Also, research and development personnel tend to thrive in a dynamic 

environment. 

Of course, dynamic, heterogeneous environments increase the risk of system failures. 

Placing tasks requiring such an environment outside of the primary data path (i.e., to 

outlets) makes sense. It also makes sense to isolate (i.e., modularize) interpretation tasks 

that require higher and lower degrees of reliability. For example, an interpretation outlet 

acting as a trusted source for emergency managers must function, even when software 

under development fails. Conversely, scientists and engineers should do science and 

engineering instead of keeping non-critical research systems operational 24 hours a day. 

Striking a balancing between tasks and personnel favoring a centralized, standardized, 

stable environment and tasks and personnel favoring a distributed, heterogeneous, 

dynamic environment leads inevitably to treating production and interpretation in 

different ways. 

Modularization 

One way to satisfy the divergent requirements of production and interpretation is to make 

a formal separation between them. In organizational terms, this separation means that 

production and interpretation tasks would be performed by different groups of people. In 

technical terms, this separation is implemented as a clean interface between operation 

(data processing) centers and (interpretation) outlets. Notice that this separation is formal 

in the sense that it allows, but does not require that production and interpretation tasks be 

physically separated. It could imply something as simple as production and interpretation 

groups (with separate management) working side by side on separate hardware/software 

systems connected by an operation center/outlet interface. However, this same structure 

could equally well support an isolated group of researchers allowing them the same 

degree of participation in ANSS as researchers collocated with a production group. 

Of course, ANSS modularization will necessarily be far more extensive than simply 

separating production and interpretation. As we have seen, modularization (into data 

concentrators, operation centers, and archiving facilities) is required in the production 

environment by the diversity of tasks and by geography. Modularizing other production 

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tasks (into outlets) is advantageous because it isolates the load on automated real-time 

processing systems, though it does add overhead (in the operation center/outlet interface). 

Modularizing production tasks also adds considerable flexibility. For example, it allows 

tasks such as rapid review, waveform QC, and catalog construction to be performed at 

different locations if desired. Similarly, it makes sense to modularize different types of 

interpretation facilities because of the wide variety of tasks, the geographical distribution 

of participating institutions, and widely varying requirements for reliability. 

While modularizing ANSS roles and responsibilities on technical, economic, and 

community participation grounds makes sense, there is the disturbing implication of 

compartmentalizing the associated personnel. Of course, the modularization of tasks and 

the compartmentalization of personnel are ubiquitous in large organizations because 

complex projects must be broken down into manageable pieces and personnel are more 

efficient when they can specialize. However, the resulting decrease in communications 

between groups of specialists and the indirect nature of controlling an organization 

through layers of management are well known problems. Fortunately, effective strategies 

for ensuring adequate communications among groups of specialists and for ensuring that 

organizations remain responsive to the needs of customers have been developed. 

Scale Issues 

Although the compartmentalization of specialists is minimized in an ideal RSN 

environment, where a small, close knit group designs the network, deploys stations, 

writes processing code, informs the public, and conducts research, it is an open question 

whether this advantage can be maintained as the ANSS grows. Nor is it obvious that the 

role of the scientist-manager can (or should) be preserved. In fact, it is not at all clear 

that this model applies to the larger RSNs even today. For example, the Northern 

California Seismic Network (NCSN) has small, but distinct groups of specialists 

maintaining stations, maintaining the processing system, and analyzing the data. Further, 

although a scientist manages the NCSN, managing the network effectively leaves little 

time for research. 

The ANSS is projected to grow to more than three times as many stations as are currently 

operated by all of the RSNs together and to more than ten times the number of channels. 

In addition, national integration means that all of these stations and channels must be 

considered to be part of one very large system. ANSS production inevitably will require 

a full time staff of dedicated specialists including field technicians, computer hardware 

and software maintenance personnel, programmers, data base administrators, and seismic 

analysts. 

Examining other large seismological organizations (e.g., the Incorporated Research 

Institutions for Seismology (IRIS) or even the National Earthquake Information Center 

(NEIC)) suggests that some degree of compartmentalization of personnel is inevitable 

and, in fact, should be planned. The NEIC experience suggests that maintaining the role 

of the scientist-manager is pointless. Large networks require full time management. The 

IRIS experience suggests that professional managers can be beneficial, providing full 

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time management for operations and freeing scientists and engineers to specialize in 

science and engineering. 

Managing the ANSS 

While the Technical Guidelines call for modularization of tasks to provide the flexibility 

ANSS will require, it doesn’t discuss the organizational mechanisms that must be 

implemented to ensure responsiveness to both short and long-term community needs, 

interaction among groups of specialists, and interaction between the community and 

specialists. The operation and management of IRIS provides important clues about how 

these problems might be addressed. In fact, this is why the ANSS was organized along 

IRIS lines with professional management advised by a hierarchy of committees 

representing community interests. 

The National Steering Committee and the Regional Advisory Committees may be 

thought of as providing the long term guidance for ANSS evolution in much the same 

way as the IRIS Executive Committee and the Standing Committees. The IRIS 

experience indicates that the advice of the community is carried out more effectively if 

full time managers have strong geophysical backgrounds ensuring that they understand 

the needs and share the interests of the community. Similarly, the ANSS should look to 

working seismologists and engineers to fill the positions of Director and 

National/Regional (network) Coordinators. 

Of course, the ANSS also has unique management problems related to its real-time 

monitoring mission. Of particular concern is the ability of the ANSS to react to the 

community desire to focus monitoring resources on transient phenomena such as volcanic 

swarms or aftershock sequences. To address these issues, the ANSS organization 

includes the National and Regional Working Groups, a unique layer of community 

involvement, potentially dealing directly with day-to-day network issues. In addition, 

ANSS professional management should be available and responsive to the community on 

a day-to-day basis. 

The concern has been expressed that community input through the advisory committees 

and working groups is not as effective as the direct control of a scientist-manager. This is 

undoubtedly true and to some degree inevitable through the transition from a 

confederation of regional networks to a single national system serving the entire 

community. Thus far, it appears that the ANSS working groups are capable of providing 

the degree of “control” that the community desires. Undoubtedly striking the right 

balance between the needs of the national community and the local needs of particular 

institutions will be a learning experience. However, ultimately it is within the power of 

the community to ensure that the ANSS organizational structure evolves to meet their 

needs. 

IRIS has also addressed communication among groups of specialists. For example, the 

exchange of station configuration and QC information between network operations and 

maintenance personnel (part of the Global Seismograph Network (GSN)) and data 

collection personnel (part of the Data Management Center (DMC)) has been successfully 

institutionalized. Although IRIS chose to collocate operation and data collection groups, 

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these groups are managed separately. In addition, research feedback on data quality and 

data management issues has been instituted in the form of Data Problem Reports. The 

ANSS needs to consider institutionalizing similar types of communications to ensure the 

effective development and operation of the network. 

Finally, IRIS has addressed the issue of operational specialists providing seismologists 

and engineers with the information needed to make the best use of the data. For example, 

most global seismologists don't have a hands-on “feel” for the behavior of GSN field 

equipment. However, through workshops educating them in GSN data characteristics 

and direct experience with the data they have managed to adapt and to produce quality 

research. Similarly, the ANSS will make every attempt to provide seismologists and 

engineers with the information the need to make the best use of the data. 

Conclusion 

Modularizing both the organizational and technical structure of the ANSS will provide 

the flexibility needed to meet ANSS goals in an evolving organizational, technological, 

and funding environment. In particular, formally separating production and interpretation 

functions is the key to providing both a stable, reliable, cost effective production 

environment and a diverse, dynamic interpretation environment. However, this 

specialization of functions among modules potentially creates problems in 

communication and coordination between groups of specialists, in adapting production to 

meet short-term scientific goals during transient phenomena, and in providing scientific 

guidance for the evolution of the production environment. Effective strategies for 

dealing with some of these problems have evolved in other large-scale seismological 

programs. Some of these strategies have already been adopted in the ANSS management 

structure. The ANSS community requires that strategies already implemented are 

effective and that new strategies evolve as needed to ensure that the ANSS is responsive 

to their needs. 

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