The Global Seismographic Network
 

The U.S. Geological Survey’s National Earthquake Information Center reports on more than 

30,000 earthquakes a year worldwide, automatically detecting, locating, and characterizing 

events, providing alerts, maps of strong ground shaking, and impact estimates of potential 

fatalities and losses. These rapid earthquake information products, which enable the prompt 

mobilization of emergency resources by all levels of government and humanitarian organizations, 

depend on the high-quality seismic stations that make up the Global Seismographic Network. 

The Global Seismographic Network 

(GSN) is a permanent, digital network of 

more than 150 modern stations in over 80 

countries, from the South Pole to Siberia and 

from the Pacifi c basin to the southern tip of 

Africa. At the core of the GSN, are the very 

broadband, high-dynamic range seismometers that measure the vibrations of the Earth. 

These instruments are extremely sensitive 

over a wide range of frequencies and are 

capable of detecting the response of the Earth 

to the motions of the Sun and the Moon with 

periods of thousands of seconds, as well as 

the strong shaking near large earthquakes with 

periods less than a tenth of a second, with 

high fi delity. 

In many cases, these seismometers are 

combined with other sensors, such as microbarographs, anemometers, magne tometers, 

and Global Positioning System receivers, to 

form geophysical observato ries. Advanced 

systems for data acquisi tion and communications transmit continuous digital data from the 

stations to collection points in the U.S. 

The GSN was formed in 1986 as a 

partnership involving the U.S. Geological 

Survey (USGS), the National Science 

Foundation (NSF), and the Incorporated 

Research Institutions for Seismology 

(IRIS, a university consortium) and serves 

as a multi-use scientifi c facility and societal resource for monitoring, research, and 

education. All GSN data are freely and 

openly available to the public and scientists around the world from the IRIS Data 

Management Center. 

Monitoring Earthquakes and 

Other Seismic Events 

Monitoring earthquakes around the 

world is essential to the mission of the USGS 

to deliver rapid information on damaging 

events and to assess earthquake hazards 

and risks, particularly because earthquakes 

outside the boundaries of the United States 

may endanger U.S. assets and citizens overseas and create destabilizing impacts abroad 

requiring humanitarian assistance. Nearly all 

GSN stations transmit data in near-real-time, 

contributing to USGS rapid earthquake 

information products such as alerts, Web 

pages, ShakeMaps, and Prompt Assessment 

of Global Earthquakes for Response 

(PAGER) loss estimates. For example, GSN 

data enabled the USGS National Earthquake 

Information Center (NEIC) to provide within 

30 minutes a projection of the impact of the 

devastating 2010 Haiti earthquake. 

The GSN also plays a major role in 

the operations of the National Oceanic 

and Atmospheric Administration (NOAA) 

Tsunami Warning Centers in Hawaii and 

Alaska. GSN data are used by the Warning 

Centers to issue tsunami alerts in all ocean 

basins of the world within a few minutes of 

the occurrence of a tsunamigenic earthquake. 

Foreign govern ments also rely on GSN data 

for their earthquake and tsunami monitoring 

systems. In addition, more than 50 stations 

of the GSN are part of the International 

Monitoring System of the Comprehensive 

Test Ban Treaty Organiza tion (CTBTO) and 

contribute to nuclear test monitoring and 

treaty verifi cation. 

Applications to Research 

GSN data acquired during the last 

25 years have facilitated many advances 

in studies of Earth structure, earthquake 

science, and other geophysics research For 

example, GSN data have contributed to new 

understanding of the Earth’s lowermost 

Global Seismographic Network stations (triangles) are shown against a backdrop of large earthquakes 

from 2000–2010 (red circles—magnitude 6–6.9, yellow squares—magnitude 7 and larger earthquakes). 

U.S. Department of the Interior Fact Sheet 2011–3021 Printed on recycled paper U.S. Geological Survey June 2011 
PAGER 

Origin Time: Tue 2010-01-12 21:53:10 UTC (16:53:10 local) Version 1 Location: 18.45°N 72.57°W Depth: 13 km Created: 36 weeks, 2 days after earthquake 

M 7.0, HAITI REGION

Red alert for shaking-related fatalities and

economic losses. High casualties and

extensive damage are probable and the

disaster is likely widespread. Past red alerts

have required a national or international 

response. 

Estimated Fatalities		 Estimated Economic Losses 

Estimated economic losses are 20-100% 

GDP of Haiti. 

Estimated Population Exposed to Earthquake Shaking 

ESTIMATED POPULATION
	 EXPOSURE (k = x1000)
	 - -* 50k* 7,468k* 6,361k 926k 598k 2,030k 908k 118k 

ESTIMATED MODIFIED

MERCALLI INTENSITY
	

PERCEIVED SHAKING Not felt Weak 

Resistant
	

POTENTIAL
	 none none Structures 

DAMAGE Vulnerable

Structures none none 

*Estimated exposure only includes population within the map area.

Population Exposure 

Light Moderate Strong Very Strong Severe Violent Extreme 

none V. Light Light Moderate Moderate/Heavy Heavy V. Heavy 

none Light Moderate Moderate/Heavy Heavy V. Heavy V. Heavy 

population per ~1 sq. km from Landscan		 Structures: 

Overall, the population in this region resides

in structures that are highly vulnerable to

earthquake shaking, though some resistant

structures exist. The predominant vulnerable

building types are concrete/cinder block

masonry and mud wall construction. 

Historical Earthquakes (with MMI levels): 

Date		 Dist. Mag. Max Shaking

(km) MMI(#) Deaths 

2003-09-22 246 6.4 IX(132k) 1 

1984-06-24 355 5.2 V(440k) 5 

1984-06-24 342 6.7 VII(326k) 5 

Recent earthquakes in this area have caused

secondary hazards such as landslides that

might have contributed to losses. 

Selected City Exposure

from GeoNames.org 

MMI City Population 

X Petit Goave 118k
	

X Gressier 26k
	

X Grand Goave 49k
	

IX Leogane 134k
	

VIII Carrefour 442k
	

VIII Miragoane 89k 

VIII Port-au-Prince 1,235k 

VIII Delmas 73		 383k 

V Verrettes 49k 

IV Santo Domingo 2,202k 

bold cities appear on map (k = x1000) 

PAGER content is automatically generated, and does not consider secondary hazards in loss

calculations. Limitations of input data, shaking estimates, and loss models may add uncertainty. 

http://earthquake.usgs.gov/pager Event ID: us2010rja6 

Under the auspices 


of the USGS and its 


partners, today’s Global 


Seismographic Network 


supports the Nation’s 


security, earthquake 


disaster response, and 


scientifi c research needs. 


mantle and core, including the discovery of 

the fi ne structure in the inner core, maps of 

mantle strain that reveal details of mantle 

deformation, observations of “slow earthquakes,” some of which may be ice quakes 

associated with movement of glaciers, and 

insight on the processes that govern how 

earthquake ruptures start and stop. GSN data 

have also improved the plate-tectonic framework for understanding earthquake hazards 

by providing better earthquake locations, 

more accurate models of fault slip, and other 

earthquake source parameters. 

Partnerships, Funding, 

and Operations 

Initially, the GSN was developed on 

the footprint of earlier global networks, 

including the Worldwide Standardized 

Seismograph Network and the International 

Deployment of Accelerometers. The 

principal network operators of the GSN 

are the USGS Albuquer que Seismological 

Laboratory (ASL) and the Cecil and 

Ida Green Institute of Geophysics and 

Planetary Physics, Scripps Institution of 

Oceanography, University of California at 

San Diego (UCSD), which is funded by the 

NSF through IRIS. The network is installed 

and maintained in cooperation with many 

international partners, who, in most cases, 

provide facilities to shelter the instruments 

and personnel to oversee the security and 

operation of each station. ASL and UCSD 

personnel track station and communication 

system performance, train station operators, provide routine and emergency service 

visits, and perform data quality control. 

For more information contact: 

U.S. Geological Survey 

Albuquerque Seismological Laboratory 

P.O. Box 82010
 

Albuquerque, NM 87198 USA
 

http://earthquake.usgs.gov/monitoring/gsn/

The PAGER provides fatality and economic 

loss impact estimates following signifi cant 

earthquakes worldwide. These estimates are 

generally available within 30 minutes and are 

updated as more information becomes available. 

Rapid estimates include the number of people 

and names of cities exposed to each shaking 

intensity level as well as the likely ranges of 

fatalities and economic losses. 

The GSN is coordinated with international 

efforts through the Federation of Digital 

Seismograph Networks. 

The planned lifetime of the completed 

network is 30 years, but with continued 

improvements and equipment enhancements, 

the network should operate indefi nitely. 

The GSN is currently being upgraded and 

standardized with “state-of-the-art” digital 

data acquisition systems. USGS allocated 

$4.7 million of its American Recovery and 

Reinvestment Act (ARRA) funding to these 

upgrades, and NSF also devoted $5 million of 

ARRA-enabled funds to the effort. Together, 

these allocations and ongoing support will 

allow the completion of the current GSN 

modernization effort over the next few years. 

Over the past half century, multipurpose 

seismic monitoring of the Earth has evolved 

into the world’s leading system for detecting, 

analyzing, and reporting on earthquakes and 

other events that create seismic signals. 

As one of the four federal agency 

partners in the congressionally authorized 

National Earthquake Hazard Reduction 

Program (NEHRP), the USGS is responsible 

for monitoring seismic activity, assessing 

earthquake risks, evaluating earthquake 

predictions, and conducting research to 

characterize and identify earthquake hazards. 

The Incorporated Research Institutions for 

Seismology (IRIS) is a university consortium 

sponsored by the NSF, a partner in NEHRP. 

IRIS is dedicated to the operation of scientifi c 

facilities for the acquisition, management, and 

distribution of freely available seismic data. 

The USGS, NSF, and IRIS are dedicated to 

providing high-quality seismological data for 

hazards reduction and research. 

—Lind S. Gee and William S. Leith 

The IRIS Consortium 

1200 New York Ave. NW, Suite 800 

Washington, DC 20005 USA 

http://www.iris.edu/hq/programs/gsn

This Fact Sheet is available online at http://pubs.usgs.gov/fs/2011/3021