Prepared for U.S. Geological Survey and the

Advanced National Seismic System National Implementation Committee

Instrumentation Guidelines for the Advanced 

National Seismic System

Open-File Report 2008–1262

U.S. Department of the Interior

U.S. Geological Survey

Prepared for U.S. Geological Survey and the 

Advanced National Seismic System National Implementation Committee 

Instrumentation Guidelines for the Advanced 

National Seismic System 

By the Working Group on Instrumentation, Siting, Installation, and Site Metadata of the Advanced National Seismic 

System Technical Integration Committee 

Open-File Report 2008–1262 

U.S. Department of the Interior 

U.S. Geological Survey 
U.S. Department of the Interior 

DIRK KEMPTHORNE, Secretary 

U.S. Geological Survey 

Mark D. Myers, Director 

U.S. Geological Survey, Reston, Virginia: 2008 

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Working Group on Instrumentation, Siting, Installation, and Site Metadata, 2008, Instrumentation guidelines for the 

Advanced National Seismic System: U.S. Geological Survey Open-File Report 2008–1262, 41 p.

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reproduce any copyrighted material contained within this report. 

ii
CONTENTS 

TABLES........................................................................................................................................................................................iv

ABBREVIATIONS USED IN THIS REPORT .........................................................................................................................iv

1 PREFACE............................................................................................................................................................................... 1

2 INTRODUCTION .................................................................................................................................................................. 2

3 DATA NEEDS AND TYPES OF SEISMIC MONITORING STATIONS ....................................................................... 3

3.1 DATA NEEDS.................................................................................................................................................................... 3

3.2 TYPES OF ANSS SEISMIC MONITORING STATIONS........................................................................................................ 4

4 GENERAL INSTRUMENTATION CONSIDERATIONS ................................................................................................ 9

4.1 SYSTEM PERFORMANCE.................................................................................................................................................. 9

4.2 GENERAL DESIGN CONCEPTS......................................................................................................................................... 9

4.3 GENERAL EXPECTATIONS.............................................................................................................................................. 12

4.3.1 Robustness.............................................................................................................................................................. 12

4.3.2 Bandwidth .............................................................................................................................................................. 12

4.3.3 Operating Range .................................................................................................................................................... 12

4.3.4 Resolution............................................................................................................................................................... 13

4.3.5 Data Latency.......................................................................................................................................................... 13

4.3.6 Siting ...................................................................................................................................................................... 14

5 INSTRUMENTATION CLASSES ..................................................................................................................................... 14

5.1 PURPOSE ......................................................................................................................................................................... 14

5.2 ANSS INSTRUMENTATION DEFINITIONS......................................................................................................................... 15

5.3 APPLICATION-BASED CLASSIFICATION........................................................................................................................... 17

5.4 STRONG-MOTION MONITORING SYSTEM CLASSIFICATION............................................................................................. 19

6 FUNCTIONAL PERFORMANCE SPECIFICATIONS .................................................................................................. 20

6.1 SCOPE ............................................................................................................................................................................. 20

6.2 MONITORING STATION PERFORMANCE........................................................................................................................... 20

6.2.1 National Monitoring Stations................................................................................................................................. 20

6.2.2 Regional Monitoring Stations ................................................................................................................................ 21

6.2.3 Urban Monitoring Stations .................................................................................................................................... 21

6.2.4 Structural-Response Monitoring Stations .............................................................................................................. 22

6.3 SENSOR SPECIFICATIONS ................................................................................................................................................ 22

6.4 DATA ACQUISITION UNIT (DAU) SPECIFICATIONS......................................................................................................... 25

6.5 POWER AND PACKAGING ................................................................................................................................................ 26

6.5.1 National Station ..................................................................................................................................................... 29

6.5.2 Regional Station..................................................................................................................................................... 30

6.5.3 Urban Monitoring Station...................................................................................................................................... 31

6.5.4 Engineered Civil System Response Monitoring Stations........................................................................................ 32

7 SYSTEM ISSUES................................................................................................................................................................. 33

8 TESTING GUIDELINES .................................................................................................................................................... 35

8.1 OVERVIEW...................................................................................................................................................................... 35

8.2 VALIDATION TESTING..................................................................................................................................................... 35

8.3 PERFORMANCE VERIFICATION TESTING ....................................................................................................................... 36

8.4 POST-AWARD TESTING ................................................................................................................................................. 36

8.4.1 Acceptance Tests .................................................................................................................................................... 37

8.4.2 Routine Operational Tests...................................................................................................................................... 37

8.4.3 NIST-Traceable Calibrations................................................................................................................................. 37

9 REFERENCES CITED........................................................................................................................................................ 39

10 APPENDIX: THE WORKING GROUP ON INSTRUMENTATION, SITING, INSTALLATION, 

AND SITE METADATA ................................................................................................................................................... 41

iii
Tables 

1. Selection of instrumentation type and class by ANSS application .............................................18 

2. Strong-motion system classification ...........................................................................................19 

3–5. Performance specifications of: 

3. Sensors...................................................................................................................................23 

4. Data acquisition units ............................................................................................................26 

5. Power and packaging .............................................................................................................28 

Abbreviations Used in This Report 

μg one millionth of 1 g acceleration 

g acceleration due to gravity at the Earth’s surface 

rms root-mean-square of a given data set 

sps samples per second 

ADC analog to digital converter 

ANSS Advanced National Seismic System 

DAS data acquisition system 

DAU data acquisition unit 

GPS global positioning system 

IASPEI International Association of Seismology and Physics of the Earth's Interior 

M earthquake magnitude 

NIST National Institute of Standards and Technology 

NTP network time protocol 

PSD power spectral density 

SOH state of health (message) 

U.S. United States 

VDC volts, direct current 

Conversion Factors 

 SI to Inch/Pound 

Multiply By To obtain 

kilometer (km) 0.6214 mile (mi) 

meter per second (m/s) 3.281 foot per second (ft/s) 

iv
Instrumentation Guidelines for the 

Advanced National Seismic System 

By the Working Group on Instrumentation, Siting, Installation, and Site Metadata of the Advanced National 

Seismic System Technical Integration Committee 

1 Preface 

This document is a result of the efforts of Working Group D of the Advanced National 

Seismic System (ANSS) National Technical Implementation Committee to rewrite Chapter 3 of 

the 2002 ANSS Technical Implementation Guideline document (U.S. Geological Survey, 2002). 

During 2004 through 2006, Working Group D revised the original Chapter 3 many times and 

obtained outside review by a broad spectrum of scientists and seismic instrumentation vendors. 

We have taken the results of the Chapter 3 revision and created this stand-alone document to 

address ANSS’s need for guidance in its planning for and procurement of new instrumentation. 

Members of the Working Group on Instrumentation, Siting, Installation, and Site Metadata 

are listed in the appendix. A copy of this document and supporting materials, including any 

subsequent modifications, may be found at 

http://earthquake.usgs.gov/research/monitoring/anss/documents.php (accessed 15 July 2008). 

1
2 Introduction 

This document provides guidelines for the seismic-monitoring instrumentation used by longterm earthquake-monitoring stations that will sense ground motion, digitize and store the 

resulting signals in a local data acquisition unit, and optionally transmit these digital data. These 

guidelines are derived from specifications and requirements for data needed to address the 

nation’s emergency response, engineering, and scientific needs as identified in U.S. Geological 

Survey Circular 1188 (1999). Data needs are discussed in terms of national, regional, and urban 

scales of monitoring in section 3. Functional performance specifications for instrumentation are 

introduced in section 4.3 and discussed in detail in section 6 in terms of instrument classes and 

definitions described in section 5. System aspects and testing recommendations are discussed in 

sections 7 and 8, respectively. 

Although U.S. Geological Survey Circular 1188 (1999) recommends that the ANSS include 

portable instrumentation, performance specifications for this element are not specifically 

addressed in this document. Nevertheless, these guidelines are largely applicable to portable 

instrumentation. Volcano monitoring instrumentation is also beyond the scope of this document. 

Guidance for ANSS structural-response monitoring is discussed briefly herein but details are 

deferred to the ANSS document by the ANSS Structural Response Monitoring Committee (U.S. 

Geological Survey, 2005). Aspects of station planning, siting, and installation other than 

instrumentation are beyond the scope of this document. 

2
3 Data Needs and Types of Seismic Monitoring Stations 

3.1 Data Needs 

Guidance for ANSS earthquake monitoring stations includes planning, siting, and installation 

of suitable instrumentation, all collectively intended to yield the data required to address the 

goals of the ANSS. Thus the guidance for different types of stations flows directly from ANSS 

goals and hence from requisite characteristics of data. To meet ANSS performance standards, 

ANSS data must include measurements that provide the following: 

• National monitoring adequate to locate and determine the magnitudes of M≥3.0 and 

larger earthquakes and to quantify salient properties such as focal depth, magnitude, and 

source characteristics. 

• Regional monitoring adequate to provide detailed information about scientifically or 

societally important earthquake source regions and zones, such as active faults. Events 

with magnitudes as small as the M2.0–2.5 magnitude completeness level should be 

observed sufficiently well to determine their location and magnitude. Of particular 

importance for scientific and engineering purposes is detailed on-scale recording of large 

earthquakes within 20 km. ShakeMap, earthquake catalogs, and early warning are 

examples of important ANSS products that depend upon regional monitoring data. 

• Ground shaking from felt or damaging earthquakes for scientific and engineering uses, 

preparation of ShakeMap, rapid response or early warning, public information, and other 

purposes. The ANSS has prioritized 26 urban areas for ground shaking monitoring. 

• Detailed response characteristics of engineered civil systems—buildings, geosystems 

(such as embankments and earthen dams), and infrastructure (such as bridges and other 

3
transportation and utility system components)—for use in improving understanding and 

predictive modeling of the response of structures and in aiding the response to and 

recovery from earthquakes. 

3.2 Types of ANSS Seismic Monitoring Stations 

The monitoring systems in the ANSS, as defined in U.S. Geological Survey Circular 1188

(1999), are characterized in terms of the national backbone network, regional networks, and 

urban monitoring networks. The concept of national-, regional-, and urban-scale monitoring is 

readily understandable by Federal and State funding agencies and officials and by the general 

public. However, based on the experience of the initial five years of the ANSS, some refinement 

within these categories is needed to provide an up-to-date framework for selecting and 

instrumenting sites as ANSS stations. The traditional distinctions between national, regional, and 

urban stations, described respectively as having broadband, high-gain short-period, and strongmotion instruments, have blurred. In particular, the various networks have evolved to more 

effectively monitor and record the continuum of earthquake-caused motions at all frequencies 

and amplitudes. Another practical consideration relates to budget constraints on full funding; the 

ANSS now requires an evolutionary approach to achieve its modernization (and other) goals. 

Thus these revised instrumentation guidelines provide for the inclusion of some legacy seismic 

instrumentation, consistent with a longer development time and lower rate of capital investment 

for the ANSS. 

In this section, four categories of ANSS seismic-monitoring stations are identified: national, 

regional, and urban monitoring stations, along with a separate category for specialized 

instrumentation of structures. The first three categories of station monitor vibratory ground 

motions; the fourth monitors structural response to these ground motions. As detailed below, 

4
although these categories do not represent any fundamental change from categories described in 

U.S. Geological Survey Circular 1188 (1999), their refined description improves the framework 

that guides the planning and design of ANSS seismic monitoring stations and the performance of 

their instrumentation. 

National monitoring stations are elements of a broad grid or network deployed on a 

national to global scale (station spacing of hundreds of kilometers) intended to provide uniform 

seismographic surveillance of the United States and its territories and to support the detection of 

nuclear tests and tsunamigenic earthquakes outside United States boundaries. Within the ANSS 

framework, these stations generally are elements of the ANSS–EarthScope national backbone 

array, the legacy U.S. National Seismic Network, or the Global Seismic Network. Operational 

responsibilities for these stations currently fall to the U.S. Geological Survey (USGS) in 

partnership with the National Science Foundation through its Incorporated Research Institutions 

for Seismology (IRIS)-managed programs. National-scale monitoring emphasizes the recording 

of longer-period data at very low noise sites with sensitive, low-noise seismographs; 

accelerometers are included to assure on-scale records of strong shaking, but the placement of 

the sensors may not meet the requirements of engineering users of strong-motion data. 

Regional monitoring stations are elements of regional-to-local-scale grids or networks 

(station spacing of ~100 km to ~10 km) deployed for the systematic seismic surveillance of all or 

part of a regional seismic belt, ANSS region, or State jurisdiction, or for high-resolution 

monitoring of active faults and other seismic source zones within those domains. Within the 

ANSS framework, such stations generally have been elements of traditional regional seismic 

networks. Regional monitoring stations require diverse instrumentation and variable station 

spacing to meet different requirements, such as the assured on-scale recording of moderate to 

large local earthquakes, high-quality broadband waveforms for moment-tensor inversions, the 

5
detection and fine spatial resolution of microseismicity associated with active faults, and nearfault recording of strong earthquake ground shaking on both rock and soils needed for 

earthquake-engineering purposes. These strong-motion records are also an important component 

of ShakeMap and early warning ANSS products. 

Some local-scale monitoring within ANSS regions may be carried out by entities in 

coordination with the ANSS, such as seismovolcanic monitoring by the USGS volcano 

observatories, or in some cases independent of the ANSS, such as local monitoring (by public- or 

private-sector groups) of seismicity associated with impounded reservoirs, geothermal fields, 

nuclear and other critical facilities, and mining operations. Regional-scale monitoring and localscale monitoring are invariably complementary in space and time, and real-time monitoring and 

response should be coordinated to the greatest extent possible. In the case of volcano monitoring, 

regional monitoring stations not only provide information about the surrounding tectonic setting 

(relevant to the interaction between volcanic and tectonic processes), but they also provide 

backup on-scale recording in the event of large eruptions that can cause the volcano-monitoring 

stations to go off scale or even to be destroyed. 

Urban monitoring stations are designed for on-scale high-fidelity recording of seismic 

ground motions in the built environment, especially in areas of moderate to high seismic hazard 

and high seismic risk. In near real-time (minutes) after an earthquake, Urban monitoring stations 

provide vital information on the severity and extent of actual ground shaking for impact 

assessment and emergency response. They also inform earthquake engineers about ground 

motions that were entered into structural-response monitoring stations, and their data enable 

predictive modeling of ground shaking in future earthquakes and thus help to improve seismic 

design and assessment of earthquake damage to structures immediately after an earthquake. In 

some areas, feasibility studies are underway aimed at using urban monitoring stations (combined 

6
with regional stations) for early warning of a destructive earthquake that is in progress. Urban 

monitoring stations will have high clipping levels. Where active faults are close, the 

instrumentation may provide good on-scale P- and S-wave waveforms for locating 

microearthquakes (depending on the urban noise levels). 

Dense arrays of urban monitoring stations are arrays with small interstation spacing. 

Currently, urban monitoring stations are typically 3 to 4 km apart. The variability of ground 

motions recorded by nearby stations is high and not easily estimated unless the station spacing is 

reduced to about 1 km or less (Boore and others, 2003). Such dense arrays of urban monitoring 

stations are thus needed to confidently interpolate ground motions for use in detailed postearthquake (minutes to months after a damaging earthquake) urban-damage assessments and for 

other purposes. The dense arrays may be formed as “nested arrays” (Evans and others, 2005), 

anchored with state-of-the-art class A (see section 5) instrumentation and augmented by class B 

or other instrumentation. Nested arrays provide high spatial resolution in high priority areas 

likely to experience moderate to major earthquakes in coming decades and that have one or more 

of the following characteristics: (1) urban centers with dense populations and dense 

infrastructure; (2) near-source regions, giving preference to those in and near urban and suburban 

areas; (3) urban and suburban regions thought likely to suffer from localized effects, such as 

basin-edge or strong site effects, causing neighborhood-scale “hot spots” of high shaking 

strength; or (4) National Earthquake Hazard Reduction Program site-class E soils (and the 

adjacent area) for which few data currently exist but upon which, in some regions, is significant 

urban and infrastructure development. 

Structural-response monitoring stations are arrays of sensors installed in and on 

structures—buildings, geosystems (geotechnically engineered structures such as landfills and 

dams), and infrastructure (principally utilities and transportation systems)—to measure the 

7
earthquake response of such engineered civil systems. Dense geotechnical arrays may augment 

this class of ANSS stations. 

Structure monitoring requires engineering design of the sensor layout and specifications of 

sensors and data acquisition systems to properly address the application of these data to 

improving understanding and predictive modeling of engineered civil systems. It is this 

understanding that leads to advances in seismic design codes and practices and in damage 

assessment and other immediate post-earthquake activities. Details are beyond the scope of this 

document but can be found in the ANSS document by the ANSS Structural Response Monitoring 

Committee (U.S. Geological Survey, 2005). 

8
4 General Instrumentation Considerations 

4.1 System Performance 

The data needs stated in the previous section naturally lead to overall system performance 

requirements for seismic instrumentation. Generically, the monitoring station instrumentation 

system (from sensors through data communications) should achieve the following performance: 

• Accurate waveforms from first P-wave through surface waves 

• On-scale waveforms for all potential earthquakes 

• Accurate absolute timing of every sample throughout the record 

• Minimum loss of data owing to malfunction of instrumentation or data communication 

• Timely transmission of continuous or segmented data for the required analysis 

applications, including ShakeMap and early warning 

• Minimum internal and external contamination by nonseismic noise 

• Consistent performance under field conditions. 

Detailed specifications for instrumentation performance are provided in section 6 for each of 

the categories of ANSS monitoring stations. These specifications follow from the system 

performance goals above. 

4.2 General Design Concepts 

Seismic station and network design are evolving practices, driven by both changing data 

needs and technological advances. A recent snapshot of the state of practice is found in the 

International Association of Seismology and Physics of the Earth's Interior (IASPEI) New 

9
Manual on Seismic Observatory Practice (http://www.iaspei.org, 2002; accessed 15 July 2008). 

The design and implementation of ANSS instrumentation is part of this evolution, and this 

document attempts to provide guidance and organization. 

Within this context, many basic decisions about the desired performance of ANSS stations 

either have been or can be made on the basis of experience, technological trends, and the stated 

goals of the ANSS. These decisions include the following: 

• The need for wide bandwidths and linear high operating range generally dictates 

feedback sensor designs. 

• The need for high resolution dictates onsite digital recording and digital telemetry. 

• Seismological research and engineering practice and research require a minimum of 

three-component linear-motion data. Nevertheless, there is still a useful role in 

monitoring active faults for single-component, high-gain, short-period sensors in regional 

or urban monitoring stations that complement three-component translational 

accelerometers. 

• The issue of the three rotational components of motion is a rapidly evolving field of 

uncertain outcome that may affect the minimum appropriate number of inertial sensors in 

an ANSS station. 

• Technological trends suggest standardizing on Internet protocols (e.g., TCP/IP) for data 

communication, although use of current and future transmission media options should not 

be limited. 

• Strong-motion data should have continuous access to telemetry whenever possible and 

practical. However, if cost or technical issues render continuous telemetry impractical, 

10
dial-up telephone or other intermittent connections are satisfactory if engineered for 

latency of not more than a few minutes. 

• Stations with limited continuous telemetry bandwidth can be accommodated by triggered 

full-sample-rate event recording, compressing all data, and adopting the highest sample 

rates consistent with requirements for continuous data transfer. 

• The need for complete data implies onsite buffering or backup storage lasting days or 

longer for all types of stations. 

• Reliable communications require error correction and packet retransmission, which 

implies bidirectional communication. Variable communications latency requires either 

onsite timing or network-based timing with adequate accuracy. 

• Maintenance and reliability concerns similarly imply bidirectional communication and at 

least daily state-of-health (SOH) messaging from the instrument. 

• Small data-delivery latency, an important requirement for early warning, requires short 

packets and reasonably fast communication speeds with minimal (<1 second transit time) 

routing or buffering delays. 

• Instrumentation systems should be warranted for at least 1 year, and 3 years is desirable; 

vendors should provide spare parts and service for their systems for at least 10 years after 

purchase. 

11
4.3 General Expectations 

4.3.1 Robustness 

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

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

environments (extreme temperatures, moisture, "dirty" power, other hazards). 

4.3.2 Bandwidth 

The station instrumentation’s bandwidth is the range of ground motion frequencies that can 

be accurately reproduced by the resulting digital data. The overall system bandwidth is a product 

of the sensor, cabling, and digitizer bandwidths in the field environment of a station. Bandwidth 

goals for national stations are based on U.S. National Seismic Network functional specifications 

and are nominally 0.01–50 Hz. The low-frequency specification is based on research needs, 

whereas the high frequency specification is limited by attenuation at distances comparable with 

the interstation spacing and by interoperability with regional and urban networks. Bandwidths 

for regional and urban stations, which are based on experience and identified scientific and 

engineering needs, are nominally 0.02–50 Hz. 

4.3.3 Operating Range 

The instrumentation system’s operating range is the range of amplitudes that can be 

accurately measured, bounded below by measures of system and site noise or digital resolution 

and bounded above by the sensor or digitizer clip level. Note that comparing the clipping 

behavior of transient seismic signals (representable as the rms of a just-clipping sine wave, for 

example) to an underlying noise level (representable as an rms spectral density, for example) is 

formally ill posed. Given this fact, the notions of dynamic range and signal-to-noise ratio are 

undefined. Thus, many investigators have made various arbitrary choices believed to represent 

12
practical instrument operational conditions. These choices yield results generally called 

“operating ranges” or “operating-range diagrams” (ORDs). The ANSS formally adopts the 

detailed methods defined for the Guidelines for Seismometer Testing (GST) as exemplified by 

J.R. Evans, C.R. Hutt, J.M. Steim, and R.L. Nigbor (written commun., 2008) and recognizes 

only their “ampORD” and “sdORD”, the former definitively and the latter simply as an 

illustration of likely instrument performance in frequency-domain analyses. In general terms, we 

define the ampORD range as a ratio of rms values—that of a maximum unclipped sine wave to 

that of the self-noise floor summed over half octaves. We use time series at particular sampling 

rates (40 and 200 sps) and of particular durations (218 to 220 samples), defined for each 

instrument type, and take the Walsh-method PSD using defined numbers of 50-percentoverlapping Hann-windowed subsegments. The details of this algorithm are described by those 

authors and embodied in the MatLabTM scripts “GST_NoiseAndRangeStandard.m,” 

“GST_NormalizedWelch.m,” and related functions, available on-line at 

http://earthquake.usgs.gov/research/monitoring/anss/documents.php (accessed 15 July 2008). 

4.3.4 Resolution 

The amplitude resolution of a network of instruments is limited by the system noise, 

bandwidth, self noise and ambient site noise, and the operating range of the instruments. Spatial 

resolution is limited primarily by the spacing between instruments compared not so much to 

horizontal wave numbers of the data but to the spatial covariance of observational phenomena. 

4.3.5 Data Latency 

Latencies of only a few seconds for the data at various types of stations are needed to support 

ShakeMap generation and early warning applications. The combination of onsite storage and 

short latencies requires that transmission of old data be caught up while current data continue to 

13
flow uninterrupted. That is, after a communications outage, older data should be transmitted in 

time-sequential order in parallel with the near real-time data but at a lower priority. This 

requirement also implies that both vendor-supplied and ANSS-supplied receiving software will 

tolerate and properly manage and resequence such out-of-sequence catchup data. 

4.3.6 Siting 

Although siting is the province of another portion of ANSS guidance, we note that all 

sensors—broadband, short period, and acceleration—require some degree of temperature 

stability to yield useful records; thus, they require thermal insulation. It has not always been the 

practice to insulate accelerometers and short-period sensors, but we note significant temperature 

sensitivity in both types of sensor and a particular need for very good baseline stability in 

acceleration records (which are commonly doubly integrated). Thus, accelerometers and 

accelerographs require much more thermal insulation than previously applied. Copper-coil 

geophones should also be insulated at least moderately from diurnal cycling and rapid changes 

due to local conditions such as sunlight and shadow. Most modern broadband sensors, of course, 

require heavy thermal insulation. 

5 Instrumentation Classes 

5.1 Purpose 

This section defines classes of instrumentation based upon data type and quality. These 

classes, coupled with the types of ANSS monitoring stations defined in section 3.2, provide the 

framework for organizing performance specifications in section 6. 

14
5.2 ANSS Instrumentation Definitions 

Accelerometer: A sensor that measures acceleration, commonly used as a strong-motion sensor 

in urban and structural-response networks as well as in national and regional systems to 

guarantee on-scale recording of moderate and large nearby earthquakes. 

BB: Broadband sensor or data acquisition system (DAS); measures seismic motions with wide 

frequency and amplitude limits generally reaching down to or below site ambient noise. 

Frequency response includes the long periods/low frequencies needed for global and 

national seismology purposes. 

Class A: Class A instruments (and finer distinctions such as “A–” and “A+”) are sensors and data 

acquisition units at or near the state of the art, currently about 20 to 26 bits resolution in 

the operating range of the corresponding sensor types. 

Class B: Class B instruments (and finer distinctions such as “B–” and “B+”) are sensors and data 

acquisition units that are the next step down in resolution from Class A, currently about 

16 to 19 bits resolution in the operating range of the corresponding sensor types. 

Class C: Class C instruments (and finer distinctions “C–” and “C+”) are sensors and data 

acquisition units lower still in resolution, currently about 12 to 15 bits resolution across 

the operating range of the corresponding sensor types, but which remain superior to the 

performance of legacy analog film instruments. 

Class D: Class D instruments are sensors and data acquisition units with performance 

comparable to that of legacy analog instruments, about 8 to 11 bits digital resolution or 

using analog recording. 

15
DAS: Data acquisition system, a complete seismic monitoring system containing one or more 

sensors and data acquisition units, and communications hardware. Note that a data 

acquisition system = a data acquisition unit + sensors. 

DAU: Data acquisition unit, a subsystem that acquires, stores, and transmits digital data from 

one or more sensors. Note that a data acquisition unit = amplifiers + ADC + storage + 

telemetry + timing source (global positioning system, NTP, or other). 

Sensor: In the ANSS context, a sensor is a device that converts motion to an analog voltage or a 

digital signal. Ground-motion sensors typically sense translational acceleration or 

velocity, but they can also sense displacement, strain, force, or rotation. 

Seismometer: A sensor that measures velocity or acceleration. In common use, the term indicates 

a broadband or short-period sensor as distinct from a strong-motion sensor. 

ShakeMap: A map (generated by USGS and its partners) of the shaking strength observed or 

predicted for the region of strong shaking (Wald and others, 1999). 

SP: Short-period sensor or data acquisition system that has limited bandwidth at low frequencies 

(long periods); typically limited to frequencies above ~1 Hz. 

SM: Strong-motion sensor or data acquisition system, measures large amplitude motions, to date 

without the low-amplitude resolution of broadband seismometers. 

Strong-motion sensor: A seismometer or accelerometer that measures large-amplitude 

earthquake motions, up to about 3.5 g acceleration and 3.5 m/s velocity. 

Velocimeter: A seismometer or other device sensing ground velocity. 

16
5.3 Application-Based Classification 

Several types and classes of instrumentation (including both sensors and DAUs) possess 

capabilities that span the different ANSS monitoring needs described in section 3 above. Table 1 

indicates which instrument type and class are appropriate for each ANSS station type and 

monitoring application. See the previous section for definitions of the various instrument types 

and classes. 

A table entry of “Primary” indicates that this instrument is the type and class generally 

recommended for the application. A table entry of “Option” indicates an acceptable 

instrumentation option or a preferred system in the case of atypical siting conditions or economic 

and operational limitations. 

(Note that "interstation spacing" in table 1 and elsewhere is an approximate average. It is 

often more realistic to aim for roughly constant interstation spacing but to constrain more closely 

the equivalent area (in square kilometers) covered be a given station. The conversion, assuming 

two-dimensional hexagonal symmetry for the array design, is A = 3

4 ξ2 ≈ 0.433ξ2

, where A is 

area per station (km2

) and ξ is the interstation spacing (km) obtained from table 1. A can be 

estimated by dividing the total area of the array by the number of stations in the array, with loose 

margins around the array, by about ξ/2, to compute the area.) 

17
Table 1: Selection of Instrumentation Type and Class by ANSS Application 

18
5.4 Strong-Motion Monitoring System Classification 

Although strong-motion monitoring is included in the scope of the application-based 

classification in the previous section, it is distinct enough to warrant additional discussion. 

In addition to the current and planned ANSS urban monitoring stations, there are plans for 

development of a higher density of stations in some urban areas by using lower-cost and lowerresolution instruments. "Urban dense" stations may be operated by private industry, amateurs, 

schools, and sometimes by the ANSS. Although of lower amplitude resolution than the primary 

ANSS urban instruments, these stations will yield valuable results for ANSS engineering and 

research. They will add spatial resolution to ANSS networks and are useful also in situations 

where budgets are limited or sites are noisy. 

Table 2 defines classes A–D of strong-motion systems in terms of resolution and estimated 

cost. 

Resolution in table 2 is defined by the ampORD analysis of J.R. Evans, C.R. Hutt, 

J.M. Steim, and R.L. Nigbor (written commun., 2008). 

Cost is an estimate of the current retail cost (quantity 1) for a complete strong-motion DAS 

from sensors through DAU through communications hardware. 

Table 2. Strong-motion system classification. 

[DAS, data acquisition center; dB, decibels; μg, micrograms] 

DAS dynamic range (broadband) Strong-motion 

DAS class 

DAS resolution 

(μg) dB Bits 

Approximate 2007 cost 

of one DAS 

(US $) 

A <7 >111 ≥20 10,000 

B 7–107 87−111 ≥16 to 20 5,000 

C 107−1709 63−87 ≥12 to <16 3,000 

D ≥1709 <63 <12 1,000 

19
6 Functional Performance Specifications 

6.1 Scope 

“Functional performance specifications” are defined herein as detailed criteria or metrics for 

the desired levels of performance from numerous elements of ANSS instrumentation. These 

specifications were developed from the ANSS data needs summarized in section 3.1. 

The specifications in this section are not intended to be directly used as procurement 

specifications but are a resource for procurement of ANSS and ANSS-compatible seismic 

instrumentation. Vendors should adhere to procurement requirements. 

The following sections present station performance goals, specifications for sensors, 

specifications for DAUs, and commentary for each ANSS monitoring-station type. 

6.2 Monitoring Station Performance 

Overall functional performance goals for each type of ANSS monitoring station are provided 

below. 

6.2.1 National Monitoring Stations 

National stations must meet the diverse needs of national and global source monitoring and 

the needs of national and global earthquake research, and they must capture strong ground 

motion for nearby events. They should also be interoperable with regional stations, at least 

matching their performance. Specific performance requirements are as follows: 

• High resolution in the band 0.01–15 Hz (0.00278–15 Hz for global stations), on-scale 

recording, and latencies less than about 30 s. 

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• Resolution below ambient noise in the band 0.04–10 Hz (0.00278–10 Hz for global 

stations), on-scale recording, high fidelity, and complete continuous data. 

• Upper band limit of 50 Hz, thus 100–200 sps, where interoperable with and supporting 

regional stations sampling at those rates. 

• For the strong ground motion component, sensitivity in the band 0.02–50 Hz, a clip level 

of 3.5 g, constant absolute sensitivity, low hysteresis, and ≥200 sample-per-second 

recording. 

6.2.2 Regional Monitoring Stations 

Regional stations must monitor both small and infrequent events, meet the needs of national 

and regional seismological research, and capture strong ground motions. Specific performance 

requirements are as follows: 

• High resolution in the band 0.02 to 35 Hz, on-scale recording, sampling at least at 

100 sps and preferably 200 sps (to oversample for better time resolution or to allow for 

the transition band of analog anti-alias filters), and latencies less than about 10 s. 

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

fidelity, and complete, continuous data. 

• For the strong ground motion component, sensitivity in the band 0.02–50 Hz, a minimum 

clip level of 3.5 g peak, constant absolute sensitivity, low hysteresis, and at least 200 sps 

recording. 

6.2.3 Urban Monitoring Stations 

Urban monitoring stations must provide the following: (1) information about the strongmotion wave field and local site effects with little ("reference") or no ("free field") contamination 

21
from manmade structures; (2) data quickly enough to produce ShakeMaps and other information 

products within 5 min. for emergency response, public media, and rapid recovery purposes; and 

(3) broadband or short-period sensors at sites where active faults or regional planning 

considerations indicate the need. Specific performance requirements are as follows: 

• Resolutions below 100 μg over the band 0.02–50 Hz 

• On-scale recording to a minimum clip level of 3.5 g peak 

• Locally triggered data storage with optional continuous data streaming 

• Latency of a few minutes after detrigger 

• Sensitivity in the band 0.02–50 Hz, constant absolute sensitivity, low hysteresis, and 

recording to at least 200 sps. 

6.2.4 Structural-Response Monitoring Stations 

Specifications for the structural-response class of ANSS station are largely the same as those 

for urban monitoring stations. There can be unique sensors or subsystems for structural 

monitoring, such as strain, displacement, shock, or load sensors, that are not used elsewhere 

within the ANSS. Further performance requirements are found in the guidance document by the 

ANSS Structural Response Monitoring Committee (U.S. Geological Survey, 2005). 

6.3 Sensor Specifications 

Table 3 contains specifications for various performance metrics relating to sensors, including 

broadband, short-period, and strong-motion sensors. 

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Table 2: Sensor performance specifications (in two panels) 

23
24
6.4 Data Acquisition Unit (DAU) Specifications 

Table 4 contains specifications for performance metrics related to data acquisition units for 

all station types. 

6.5 Power and Packaging 

Power requirements are a critical parameter for seismic station design, and packaging of the 

system components is important for long-term reliability. Performance specifications for power 

and for several quantifiable aspects of packaging are provided in table 5. 

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Table 3: DAU performance specifications (in two panels) 

26
27
Table 4: Performance specifications for power and packaging 

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6.5.1 National Station 

Broadband weak-motion seismometers are suitable for national stations, supplemented by 

strong-motion sensors and a 200 sps data stream (table 1). Stations meeting the specifications of 

the Global Seismographic Network (GSN) would require Class BB/A+ instrumentation, with 

emphasis on low noise at long periods. National monitoring stations (interstation spacing about 

70–280 km) need to resolve higher-frequency bands, with less emphasis on the long-period band. 

The best of these stations (at low noise sites) would require Class BB/A instrumentation, 

whereas the noisiest of these stations would use Class BB/A– instrumentation. The bandwidth 

and operating range specifications listed in table 1 reflect these differing requirements. The 

maximum noncoherent sensor noise specifications were derived from contour plots across the 

United States of seismic noise in various bands, as observed by the U.S. National Seismic 

Network. 

The DAU digitizer resolution requirements are matched to the operating range of the 

seismometers. Note that all DAUs should be capable of sampling at a rate of at least 200 sps, 

which is also the preferred sample rate where practical. Less resolution is needed to resolve 

signals at higher frequencies (for instance, up to 15 Hz versus 15–30 Hz) because of typically 

higher noise levels in these bands. Also, it is well known that digitizers running at higher 

sampling rates are not capable of the high resolutions possible at lower sample rates, although 

that advantage can be recovered by properly downsampling a higher-rate data stream. 

The power system should meet the specifications listed in table 5. State-of-health (SOH) 

monitoring functions for the power system should reside entirely within the DAU and should be 

composed of the following: 

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• The DAU should sample at least once per second (and at least five times faster than the 

interval at which the state-of-health message is transmitted, whichever is faster) the ~10.8 

to 16 VDC voltage input to the DAU by the power system, as referenced to the master 

ground. This sampling should be at a resolution of 0.01 VDC or finer. 

• For the interval between state-of-health messages, the DAU should calculate the mean, 

minimum, maximum, and rms of this power voltage to a precision of 0.01 VDC or finer. 

• The DAU should report these four values in each of its state-of-health messages to an 

accuracy of 0.01 VDC or finer. 

• To facilitate diagnosis of line-power failures and other disruptions to power systems, 

DAU state-of-health messages should be reported at least four times per day and 

preferably 12 or more times per day. The DAU should, if feasible, also send an 

emergency state-of-health message containing the same information just prior to when 

the DAU shuts down for loss of power or other fault condition. 

6.5.2 Regional Station 

The seismometer may be the same as for a national station. However, the noise requirements 

are less stringent and there is a need for response to higher frequencies owing to the interstation 

spacing of about 50–70 km, implying the possible use of a different seismometer that meets these 

specific requirements. 

A single vertical or three components of short-period seismometer may be appropriate for 

some active-fault monitoring applications. These short-period components should be in addition 

to three-component strong-motion sensors. 

The DAU for a regional station needs somewhat less resolution than a DAU for a national 

station. Note that zero-phase fine-impulse-response (FIR) filters used in modern digitizers are 

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known to create acausal artifacts that can cause problems for automatic phase-arrival time picks 

from stations near an event. Despite this drawback, it is recommended that zero-phase filters 

should be used for regional stations because of the enhanced value for later research. It is 

suggested that acausal artifacts can be reduced to acceptable levels for near-real-time processing 

by attenuating high frequency energy by use of minimum-phase filters. Alternatively and 

preferably, it is possible to correct for the effects of minimum-phase filters through the use of a 

filter designed specifically for the purpose. 

6.5.3 Urban Monitoring Station

As indicated by tables 3 and 4, the ANSS is interested in 3-, 4-, and 6-channel systems. 

Further, the sensors, the DAU, and the power system may be delivered as an integrated system or 

as physically separate modular units connected with cables. 

In the latter case, the ANSS may collaborate with manufacturers to standardize connectors 

and modularization schemes. Tentatively, the sensor cable should be included with the sensor, 

the global positioning system (GPS) cables with the GPS receiver, the power cables with the 

DAU, external data-storage unit cables with that unit, and any telemetry cables with the 

telemetry transmitter. 

With 21 bits of resolution and a Class A strong-motion sensor, a magnitude 2.5 event at 10 

km epicentral distance should be well recorded for use of the entire waveform, whereas a 

magnitude 1.8 event at more than 35 km can be recorded well enough to determine the peak 

accelerations. Ambient seismic noise is likely to be the limiting factor in station performance, not 

resolution. 

For Class B strong-motion systems, the expectation is that events of primary engineering and 

emergency response interest will be well recorded, including those that are likely to exhibit 

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nonlinear soil response. Additionally, studies of the causes of spatial variation in strong ground 

motions are a critical target, beginning with nearby events of M>3, which should be well 

recorded. Life-cycle cost is a critical issue for Class B systems. It includes purchase, installation, 

and maintenance costs and may imply the ability to download system software upgrades from a 

remote server and reboot, with crash recovery. 

While most ANSS data recording uses (and in the future will to an even greater extent use) 

continuous recording, local buffering, and telemetry, there remains a need to use at least basic 

triggering to (1) assure backup recording of the critically needed rare near-fault, National 

Earthquake Hazard Reduction Program (NEHRP) site-class E, and strong urban recordings; (2) 

temporarily boost sample rates during large events, particularly at regional and national stations; 

(3) maintain the option of reducing telemetry costs by operating selected systems only in 

triggered mode; and (4) operate Class B monitoring systems principally or only in triggered 

mode to lower their life-cycle costs. 

Table 4 specifies a minimum complement of trigger algorithms and specifics but leaves open 

the field of triggering to include the range of more sophisticated triggers implemented in many 

current instrumentation DAUs. It is also desirable for users to be able to supply their own trigger 

algorithms to DAUs with a minimum of (ideally, no) manufacturer intervention and in a highlevel language such as C. 

6.5.4 Engineered Civil System Response Monitoring Stations

Specifications for this class of ANSS station are largely the same as those for urban 

monitoring stations. There can be unique sensors or subsystems for structural monitoring, such 

as strain, displacement, or load sensors, that are not generally used elsewhere within the ANSS. 

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Further commentary on this type of ANSS station is found in the guidance document by the 

ANSS Structural Response Monitoring Committee (U.S. Geological Survey, 2005). 

7 System Issues 

In addition to the element-level functional performance specifications described in the 

previous section, the design, specification, and installation of seismic systems must consider 

external environmental effects including the following: 

• Moisture: humidity, rain, snow, temporary submersion due to flooding, and salt drift near 

coastlines 

• Temperature, both high and low 

• Wind, as it may affect physical integrity of the system components as well as seismic 

noise 

• Sun, as it affects short-term thermal changes and long-term material degradation 

• Pressure, as it affects sensor noise 

• Radio frequency interference, both from external and internal sources 

• Magnetic interference from external sources 

• Rigorous anchoring of strong-motion sensors and other components at such sites to 

prevent resonance, banging, and other internal noise as well as intra-event shifting at 

±3.5 g peak. 

Some of the specifications in the previous section cover these environmental effects for 

components, but not necessarily for the overall installed systems. In addition to environmental 

33
effects, the design, specification, and installation of DASs for ANSS applications should address 

the following general system issues: 

• Need for standardization among vendors of external connectors for power, sensors, 

communications, and timing 

• Provisions for field leveling of sensors (such as leveling legs) as well as periodic 

automatic leveling, principally for broadband sensors 

• Robust anchoring of strong-motion systems and all other components at sites with strongmotion sensors 

• System and component weight (including power systems) where important, such as in 

remote field installations 

• Need for standardized control and data communications interfaces, including at least the 

ability to use a wide range of hardware and software computer platforms 

• Need for thorough documentation of components and as-installed systems to enable 

operation, maintenance, and confident use of the data 

• Maximization of remote operation and maintenance functions (for example, state-ofhealth messaging and remote adjustment of operating parameters, including at least gains, 

filter settings, sampling rates, and trigger settings). 

System issues may be network dependent and site dependent; a thorough description is 

beyond the scope of this document. 

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8 Testing Guidelines 

8.1 Overview 

In addition to manufacturers’ validation testing for their own purposes, performance may be 

verified by testing as part of the procurement process. The ANSS may test samples of all items in 

the specifications sections above that are applicable to that particular sensor, DAU, or DAS. 

Random and targeted acceptance tests of instruments (the deliverables) may be performed by the 

ANSS to verify ongoing compliance with specifications; all or portions of applicable 

specifications may be tested as deemed appropriate by the ANSS. Routine operational tests may 

be performed by the ANSS to maintain data quality and monitor ongoing performance of 

instruments, testing all or portions of applicable specifications as deemed appropriate by the 

ANSS. From time to time, the ANSS may perform or contract out National Institute of Standards 

and Technology (NIST)-traceable calibrations of various instruments to test performance of its 

networks or the compliance of deliverables to contract requirements. ANSS may during such 

calibrations test all or portions of applicable specifications, as it deems appropriate. 

The intention of vendor and ANSS testing described here is to reduce the lifecycle cost of 

these instruments and to verify their performance. Therefore, larger initial expense is tolerated 

where it is likely to reduce long-term expense, instrument failure, and uncertainty in 

performance, reliability, or the validity of the data for their intended uses. 

8.2 Validation Testing 

Validation testing by the manufacturer demonstrates that the product design satisfies its 

intended usage. Such high-level testing is generally part of the design process and as such may 

be used by vendors to prepare for performance verification tests described in section 8.3. 

35
Validation testing may be part of the vendors’ research and development, prequalification, and 

manufacturing-development processes leading to their confidence in their product. 

8.3 Performance Verification Testing 

Performance verification testing confirms that products meet specified performance 

requirements. In the ANSS context, this testing should be a formal step in which vendors 

complete formal performance verification testing (often under close ANSS observation) of final 

versions of two randomly selected sensors, two randomly selected DAUs, or two randomly 

selected DASs (depending on the item bid). These tests should meet a high level of quality 

assurance, with NIST-traceable measurement of performance metrics and within some kind of 

quality assurance environment such as International Organization for Standardization (ISO) 

9000. Test specifications should be prepared in advance of any procurement. All resulting data 

and analyses should be provided to the ANSS in sufficiently complete form that the ANSS can 

analyze the test data and confirm test results. 

It is recommended that two or more test specimens be selected at random from a batch of 

eight or more final manufactured copies of final versions of the proposed sensor, DAU, or DAS. 

The ANSS may require that tests be witnessed in person by ANSS staff or their representatives 

and possibly recorded in video and sound (by the ANSS) for documentation and external review. 

The ANSS may require that original test data be supplied to the witness for direct transfer to the 

ANSS at the time of the testing. 

8.4 Post-Award Testing 

The ANSS may perform three additional types of tests on instrumentation during 

procurement or operation, as follows: 

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8.4.1 Acceptance Tests 

Acceptance tests of randomly selected or suspect units may be performed upon delivery or 

shortly afterward to verify whether the components and systems meet ANSS contract 

specifications. If they do not, three alternatives exist: the components or systems should be 

returned to the vendor for repair; additional units of similar manufacturing lots or serial numbers 

should be tested by the ANSS; and if a pattern of vendor noncompliance emerges, the vendor’s 

history may be considered substantially unresponsive in subsequent requisitions. 

8.4.2 Routine Operational Tests 

The ANSS will perform various routine on site and laboratory operational tests to verify the 

continuing performance of the DASs and supporting systems it operates. These routine 

operational tests may include automatic self-testing by the DAS, manual or automated sensor 

tests, manual or automatic voltage checks, and other field tests by maintenance personnel. These 

tests may be similar to Acceptance or to Performance Verification testing but will generally be 

less extensive. 

8.4.3 NIST-Traceable Calibrations 

From time to time, the ANSS may deem it appropriate to perform or to contract out NISTtraceable calibrations of all or portions of particular sensors, DAUs, or DASs to monitor the 

performance of vendors and of ANSS networks. Such tests will be generally similar to all or 

portions of performance-verification tests. 

The ANSS may maintain a testing laboratory at the USGS Albuquerque Seismological 

Laboratory. It may cooperate with Sandia National Laboratory and other ANSS and IRIS 

institutions in the use of their testing facilities. Or, it may contract some tests to NIST-traceable 

testing facilities for acceptance tests, portions of routine tests, NIST-traceable calibrations, and 

37
authenticating portions of vendors’ performance-verification testing, as deemed advisable prior 

to final award of contracts (using either vendor-donated or first-article examples of the 

instruments). 

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9 References Cited 

Boore, D.M., Gibbs, J.F., Joyner, W.B., and Tinsley, J.C., 2003, Estimated ground motion from 

the 1994 Northridge, California, earthquake at the site of the Interstate 10 and La Cienega 

Boulevard bridge collapse, West Los Angeles, California: Seismological Society of America 

Bulletin, v. 93, no. 6, p. 2737–2751. 

Evans, J.R., Hamstra, Jr., R.H., Kündig, C., Camina, P., and Rogers, J.A., 2005, TREMOR—A 

wireless MEMS accelerograph for dense arrays: Earthquake Spectra, v. 21, no. 1, p. 91–124. 

International Association of Seismology and Physics of the Earth's Interior (IASPEI), 2002, New 

manual on seismic observatory practice: http://www.iaspei.org. Accessed 15 July 2008. 

MatLabTM, “GST_NoiseAndRangeStandard.m,” “GST_NormalizedWelch.m” scripts and related 

functions: http://earthquake.usgs.gov/research/monitoring/anss/documents.php. Accessed 

15 July 2008. 

U.S. Geological Survey, 1999, An assessment of seismic monitoring in the United States—

Requirements for an advanced national seismic system: U.S. Geological Survey Circular 

1188, 55 p. 

U.S. Geological Survey, ANSS Technical Integration Committee, 2002, Technical guidelines for 

the implementation of the Advanced National Seismic System—Version 1.0: U.S. Geological 

Survey Open-File Report 02-0092, 92 p., http://pubs.usgs.gov/of/2002/ofr-02-0092/ofr-02-

0092.pdf. Accessed 15 July 2008. 

U.S. Geological Survey, ANSS Structural Response Monitoring Committee, 2005, Guideline for 

ANSS seismic monitoring of engineered civil systems—Version 1.0: U.S. Geological Survey 

Open-File Report 05-1039, 49 p., http://pubs.usgs.gov/of/2005/1039/of2005-1039.pdf. 

Accessed 15 July 2008. 

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Wald, D. J., Quitoriano, V., Heaton, T.H., Kanamori, H., Scrivner, C.W., and Worden, C.B., 

1999, TriNet “ShakeMaps”—Rapid generation of instrumental ground motion and intensity 

maps for earthquakes in southern California: Earthquake Spectra, v. 15, no. 3, p. 537–555. 

40
10 Appendix: The Working Group on Instrumentation, Siting, 

Installation, and Site Metadata 

Steve Estes 

Alaska Earthquake Information Center 

Geophysical Institute 

University of Alaska 

903 Koyukuk Drive 

P.O. Box 757320 

Fairbanks, AK 99775–7320 

907–474–7425 

estes@gi.alaska.edu

John R. Evans 

U.S. Geological Survey 

345 Middlefield Rd, M.S. 977 

Menlo Park, CA 94025–3591 

650–329–4753 

jrevans@usgs.gov

Susan E. Hough 

U.S. Geological Survey 

525 S. Wilson Avenue 

Pasadena, CA 91106–3212 

626–583–7224 

hough@usgs.gov

Charles R. Hutt (chair) 

Albuquerque Seismological Laboratory 

U.S. Geological Survey 

P.O. Box 82010 

Albuquerque, NM 87198–2010 

505–846–5649 

bhutt@usgs.gov

Richard P. “Dick” Kromer 

rpkromer Consulting 

5309 Dee Drive NE 

Albuquerque, NM 87111 

505–298–3073 

rpkromer@comcast.net

Robert L. Nigbor 

University of California at Los Angeles 

Department of Civil Engineering 

Boelter Hall 5731 

Los Angeles, CA 90095–1593 

310–825–3492 

nigbor@ucla.edu

William U. Savage 

U.S. Geological Survey 

345 Middlefield Road, M.S. 977 

Menlo Park, CA 94025–3591 

650–329–4852 

wusavage@usgs.gov

Jamison Steidl 

University of California at Santa Barbara 

Institute for Crustal Studies 

Santa Barbara, CA 93106 

805–893–4905 

steidl@crustal.ucsb.edu

Robert Uhrhammer 

University of California 

Berkeley Seismological Lab 

475 McCone Hall 

Berkeley, CA 94720–4760 

510–642–8504 

bob@seismo.berkeley.edu

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Working Group on Instrumentation, Siting, Installation, and Site Metadata—Instrumentation Guidelines for the Advanced National Seismic System—Open–File 2008–1262