What is the probability that an earthquake is a foreshock to a larger earthquake?
Worldwide the probability that an earthquake will be followed within 3 days by a large earthquake nearby is somewhere just over 6%. In California, that probability is about 6%. This means that there is about a 94% chance that any earthquake will NOT be a foreshock. In California, about half of the biggest earthquakes were preceded by foreshocks; the other half were not. At this time, we cannot tell whether or not an earthquake is a foreshock until something larger happens after it... so only in retrospect.
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This Fact Sheet describes post-earthquake products and tools provided by the Advanced National Seismic System (ANSS) through the U.S. Geological Survey Earthquake Hazards Program. The focus is on products that provide situational awareness immediately after significant earthquakes.
Wald, Lisa A.
United States Geological Survey (USGS) Natural Hazards Response
The primary goal of U.S. Geological Survey (USGS) Natural Hazards Response is to ensure that the disaster response community has access to timely, accurate, and relevant geospatial products, imagery, and services during and after an emergency event. To accomplish this goal, products and services provided by the National Geospatial Program (NGP)...
Lamb, Rynn M.; Jones, Brenda K.
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Contributors: Dart, Richard; McCarthy, Jill; McCallister, Natasha; Williams, Robert A.
Earthquake hazards: a national threat
Earthquakes are one of the most costly natural hazards faced by the Nation, posing a significant risk to 75 million Americans in 39 States. The risks that earthquakes pose to society, including death, injury, and economic loss, can be greatly reduced by (1) better planning, construction, and mitigation practices before earthquakes happen, and (2)...
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This handbook provides information about the threat posed by earthquakes in the San Francisco Bay region and explains how you can prepare for, survive, and recover from these inevitable events. If you live or work in the region, you need to know why you should be concerned with earthquakes, what you can expect during and after a quake, and what...
The USGS Earthquake Hazards Program - investing in a safer future
Filson, John R.; McCarthy, Jill; Ellsworth, William L.; Zoback, Mary Lou; Stauffer, Peter H.; Hendley, James W.
USGS National Seismic Hazard Maps
The U.S. Geological Survey (USGS) recently completed new probabilistic seismic hazard maps for the United States, including Alaska and Hawaii. These hazard maps form the basis of the probabilistic component of the design maps used in the 1997 edition of the NEHRP Recommended Provisions for Seismic Regulations for New Buildings and Other Structures...
Frankel, A.D.; Mueller, C.S.; Barnhard, T.P.; Leyendecker, E.V.; Wesson, R.L.; Harmsen, S.C.; Klein, F. W.; Perkins, D.M.; Dickman, N.C.; Hanson, S.L.; Hopper, M.G. Foreshocks and aftershocks of the Great 1857 California earthquake
The San Andreas fault is the longest fault in California and one of the longest strike-slip faults anywhere in the world, yet we know little about many aspects of its behavior before, during, and after large earthquakes. We conducted a study to locate and to estimate magnitudes for the largest foreshocks and aftershocks of the 1857 M 7.9 Fort...
Meltzner, A.J.; Wald, D.J. Occurrence patterns of foreshocks to large earthquakes in the western United States
[No abstract available]
Abercrombie, R.E.; Mori, J.
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New Audiences, New Products for the National Seismic Hazard Maps
New Audiences, New Products for the National Seismic Hazard Maps
California Can Learn From Recent Large Earthquakes
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USGS Forecast for Ground Shaking Intensity from Earthquakes in 2017
USGS map displaying intensity of potential ground shaking from natural and human-induced earthquakes. There is a small chance (one percent) that ground shaking intensity will occur at this level or higher. There is a greater chance (99 percent) that ground shaking will be lower than what is displayed in these maps.
USGS Forecast for Damage from Natural and Induced Earthquakes in 2016
USGS map displaying potential to experience damage from a natural or human-induced earthquake in 2016. Chances range from less than one percent to 12 percent.
Map of Christ Church, NZ aftershocks
Map of sesmic activity near Christchurch, New Zealand, from 9/4/2010 to 4/11/2014
Earthquake-damaged building
Building damanged by the February 2011 earthquake in Christchurch, New Zealand.
1964 Alaskan Earthquake Damage
Damage from the 1964 Alaskan Earthquake. Credit: USGS
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Map of USGS “Did You Feel It?” data shows that earthquakes east of the Rocky Mountains are felt over larger areas than earthquakes in the West.
2014 National Seismic Hazard Map
2014 U.S. seismic hazard map showing the earthquake peak ground acceleration (PGA) that has a 2% chance of being exceeded in 50 years. Red indicates the highest hazard, and gray indicates the lowest hazard.