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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How do I get earthquake hazard maps for locations outside of the U.S.?

We know of no current "zone" designations for sites outside of the United States. For locations outside the United States for which seismic design is required for military facilities, there exists a standard based on probabilistic spectral ordinates in the manner of the International Building Code and are declared to reflect the 2015 version of...

How are engineers working to make roads and buildings safer?

Earthquake engineers are working to make roads and buildings safer in the event of a major earthquakes. This includes both improving the design of new buildings and bridges as well as strengthening older units to incorporate the latest advances in seismic and structural engineering. The Federal Emergency Management Agency plays a central role in...

What is the USGS doing to mitigate and respond to earthquake hazards?

The U.S. Geological Survey performs the following functions related to earthquake hazard mitigation: Receives, analyzes, maintains, and distributes data on earthquake activity worldwide. Satellites link our National Earthquake Information Center in Golden, Colorado to a network of seismograph stations. These stations, located throughout the world...

Can the National Seismic Hazard Maps be used as an earthquake forecast tool for the near future?

Not really. This web site is designed to display the probability of different sources that might occur in a several-year to several-decade period. The model bases all probability estimates on mean rate of earthquakes over long periods. As you shorten the time window, you should expect greater and greater fluctuations in what may be observed from...

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;...

Are earthquake probabilities or forecasts the same as prediction?

No. Probabilities and forecasts are rather like climate probabilities and weather forecasts, while predictions are more like statements of when, where, and how large, which is not yet possible for earthquakes. Probabilities describe the long-term chances that an earthquake of a certain magnitude will happen during a time window. Most earthquake...

How do I decide whether or not to get earthquake insurance?

You should consider the following factors when deciding whether or not to get earthquake insurance: proximity to active earthquake faults seismic history of the region (frequency of earthquakes) time since last earthquake building construction (type of building and foundation) architectural layout materials used quality of workmanship extent to...

How do earthquakes affect buildings?

Ground shaking is the primary cause of earthquake damage to man-made structures. Many factors influence the strength of earthquake shaking at a site including the earthquake's magnitude, the site's proximity to the fault, the local geology, and the soil type . More than 250 structures throughout the United States have been outfitted with seismic...

What is the likelihood of a large earthquake at location X?  Is it safe to go to X since they've been having a lot of earthquakes lately?

The National Seismic Hazards Mapping project provides an online web tool for determining the probability of a large earthquake within 50 kilometers (~31 miles) of a specific location over a certain time period. The calculation is based on the latest available information from seismic hazard data. Unified Hazard Tool - Earthquake Hazard and...

How will my house hold up in an earthquake? Can the USGS send someone out to evaluate my property?

Published maps will only provide generalized, uninterpreted information about specific areas. Every property consists of a unique combination of geologic and structural factors that must be considered to determine what might happen to a house during an earthquake. Therefore, an individual site study is necessary. Geologic factors include: type of...

What are the earthquake hazards/risks where I live?

Determining your risk with regard to earthquakes, or more precisely shaking from earthquakes, isn't as simple as finding the nearest fault. The chances of experiencing shaking from an earthquake and/or having property damage is dependent on many different factors. The National Hazard Maps use all available data to estimate the chances of shaking (...

What is seismic hazard? What is a seismic hazard map? How are they made? How are they used? Why are there different maps, and which one should I use?

Seismic hazard is the hazard associated with potential earthquakes in a particular area, and a seismic hazard map shows the relative hazards in different areas. The maps are made by considering what we currently know about: Past faults and earthquakes The behavior of seismic waves as they travel through different parts of the U.S. crust The near-...
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Date published: November 15, 2016

Assessing Critical Infrastructure Damage After Earthquakes

Early on the morning of August 24, 2014, Loren Turner was awoken by clattering window blinds, a moving bed, and the sound of water splashing out of his backyard pool. He experienced what is now named the “South Napa Earthquake.” 

Date published: June 26, 2014

New Audiences, New Products for the National Seismic Hazard Maps

New Audiences, New Products for the National Seismic Hazard Maps

Date published: April 8, 2011

California Can Learn From Recent Large Earthquakes

A new report issued by the American Red Cross and the U.S. Geological Survey documents the Chilean response and recovery efforts following the Feb. 2010 magnitude 8.8 earthquake and the lessons that California should learn from this disaster.   

Date published: April 21, 2008

Earthquake Hazard Maps Show How the Nation Shakes with Quakes

Friday's magnitude-5.2 earthquake in southern Illinois is a reminder that earthquakes are a national hazard.

Date published: January 22, 2001

New USGS Map Will Improve Earthquake Hazards Assessment in the Bay Area

A new geologic map of surficial deposits in the nine-county San Francisco Bay region that can be used to evaluate earthquake hazards has been released in digital form by the U.S. Geological Survey in Menlo Park.

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USGS Forecast for Ground Shaking Intensity from Natural and Induced Earthquakes in 2017
February 28, 2017

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
October 28, 2016

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 depicting more than 100 aftershocks that have occurred since the magnitude 7.8 earthquake in Nepal on April 25, 2015. To dat
April 18, 2016

Nepal Aftershock Map

Map of Christ Church, NZ aftershocks
December 31, 2013

Map of Christ Church, NZ aftershocks

Map of sesmic activity near Christchurch, New Zealand, from 9/4/2010 to 4/11/2014

building damaged by an earthquake
December 31, 2011

Earthquake-damaged building

Building damanged by the February 2011 earthquake in Christchurch, New Zealand.

Attribution: Natural Hazards
Image shows a road split due to earthquake damage
November 30, 2000

1964 Alaskan Earthquake Damage

Damage from the 1964 Alaskan Earthquake. Credit: USGS

East versus west earthquakes

East vs West Coast Earthquakes

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.

map of US showing seismic hazards with different colors

2014 National Seismic Hazard Map

Map of US showing seismic hazards with different colors. Red is the highest hazard and white is the lowest.