USGS ShakeMap

USGS ShakeMap
Name	USGS ShakeMap
Established	1990s
Developer	United States Geological Survey
Country	United States
Discipline	Seismology

USGS ShakeMap provides near‑real‑time maps of ground shaking intensity following earthquakes, combining instrumental observations and modeled ground motions to produce maps used by responders, media, and researchers. Developed and maintained by the United States Geological Survey in collaboration with partners, ShakeMap integrates data streams from seismic networks, global agencies, and research institutions to estimate shaking metrics such as peak ground acceleration and spectral response. Its outputs support operational decisions by agencies including the Federal Emergency Management Agency, California Governor's Office of Emergency Services, and international bodies during events like the Great Hanshin earthquake and other major seismic crises.

Overview

ShakeMap generates spatial representations of shaking intensity using observed ground motions and attenuation models for events from local to global scales. Outputs typically include maps of peak ground acceleration (PGA), peak ground velocity (PGV), and modified Mercalli intensity (MMI) for use by Emergency Alert System participants, National Oceanic and Atmospheric Administration partners, and academic centers such as the Southern California Earthquake Center and Lamont–Doherty Earth Observatory. Integration with systems like Prompt Assessment of Global Earthquakes for Response and the Global Seismographic Network enables rapid situational awareness after events such as the 2011 Tōhoku earthquake and tsunami and the Loma Prieta earthquake.

Methodology and Data Sources

ShakeMap combines seismic waveform data, strong‑motion records, and a suite of empirical ground‑motion prediction equations (GMPEs) to compute shaking estimates. Primary data sources include the Advanced National Seismic System, regional networks like the California Integrated Seismic Network, global agencies such as the International Seismological Centre, and dedicated arrays operated by institutions like University of Washington and Caltech. Algorithms merge observed station intensities with model predictions using spatial interpolation techniques and site characterization datasets such as the National Earthquake Information Center Vs30 maps and local soil databases. GMPEs used often reference work by researchers affiliated with Seismological Society of America, Pacific Northwest Seismic Network, and investigators from universities including Massachusetts Institute of Technology and University of California, Berkeley.

Products and Output Types

ShakeMap delivers raster and vector products, including contour maps, grids of PGA, PGV, spectral acceleration at multiple periods, and estimated MMI distributions. File formats typically provided are GeoTIFF, shapefiles compatible with ArcGIS, and web services consumable by platforms like OpenStreetMap and disaster portals run by United Nations Office for the Coordination of Humanitarian Affairs. Specialized outputs include population exposure estimates derived by cross‑referencing with datasets from U.S. Census Bureau and building stock vulnerability overlays informed by studies from FEMA and the National Institute of Standards and Technology. Time‑series and station plots support engineering analysis by groups such as Pacific Earthquake Engineering Research Center.

Applications and Uses

Emergency managers, engineers, insurers, media outlets, and researchers use ShakeMap for rapid damage estimation, resource allocation, and post‑event analysis. Agencies like FEMA, California Earthquake Authority, and municipal emergency offices use maps to prioritize inspections and deploy search‑and‑rescue. Insurers and reinsurers reference intensity footprints alongside loss models developed by firms collaborating with Verisk Analytics and academic centers. Scientists in organizations such as USGS Hawaiian Volcano Observatory, U.S. Geological Survey, and universities use ShakeMap outputs for aftershock forecasting with tools like Epidemic‑Type Aftershock Sequence models and for validation of ground‑motion prediction research published in journals affiliated with the American Geophysical Union.

Limitations and Accuracy

ShakeMap accuracy depends on station density, quality of site characterization, and appropriateness of GMPE selection for the tectonic setting. Sparsely instrumented regions covering territories like parts of Alaska or international locales served by limited networks can produce higher uncertainty, prompting reliance on synthetic models used by entities such as International Seismological Centre and regional research groups. Urban canyon effects, basin amplification like in the Los Angeles Basin, and complex rupture directivity as seen in events such as the 1994 Northridge earthquake can challenge accuracy. ShakeMap reports include uncertainty estimates and encourage corroboration with field surveys performed by teams from USGS and partner universities.

History and Development

Initiated in the mid‑1990s by scientists at United States Geological Survey and collaborators at institutions including California Institute of Technology and University of California, Berkeley, ShakeMap evolved from prototype systems used after the 1994 Northridge earthquake and the 1989 Loma Prieta earthquake. Continuous development has incorporated contributions from the Advanced National Seismic System, international partners like the European-Mediterranean Seismological Centre, and funding or operational support from agencies such as National Science Foundation and Department of Homeland Security. Over time, enhancements added web services, automated population exposure overlays, and integration with alerting systems used by organizations including Global Disaster Alert and Coordination System.

Category:Earthquake engineering