What is a seismic zone, or seismic hazard zone?

Although you may hear the terms “seismic zone” and “seismic hazard zone” used interchangeably, they really describe two slightly different things. A seismic zone is used to describe an area where earthquakes tend to focus; for example, the New Madrid Seismic Zone in the Central United States. A seismic hazard zone describes an area with a particular level of hazard due to earthquakes. Typically, a high seismic hazard zone is nearest a seismic zone where there are more earthquakes, and a lower seismic hazard zone is farther away from a seismic zone.

Another point of confusion is that the California Geological Survey has two sets of maps with the names “Earthquake Hazards Zones” and “Earthquake Fault Zones (Alquist-Priolo)”.

There was also a seismic zone system (0,1,2,3,4) used for building codes that is now obsolete.

 

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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...

What is the probability that an earthquake will occur in the Los Angeles Area? In the San Francisco Bay area?  

Los Angeles area: Within the next 30 years the probability is: 60% that an earthquake measuring magnitude 6.7 46% that an earthquake measuring magnitude 7 31% that an earthquake measuring magnitude 7.5 will occur in the Los Angeles region. San Francisco Bay area: Within the next 30 years the probability is: 72% that an earthquake measuring...

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 (...
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Date published: March 14, 2018

USGS Authors New Report on Seismic Hazard, Risk, and Design for South America

New seismic hazard and risk assessments can help at-risk communities prepare for future earthquake disasters

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 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 scientists conduct passive seismic study in the Washita Reach 1 study area.
October 4, 2016

USGS scientists conduct passive seismic study in the Washita Reach 1

USGS scientists conduct passive seismic study in the Washita Reach 1 study area.

Image shows an aerial view of the San Andreas Fault
November 30, 2000

San-Andreas Fault

Aerial photo of the San Andreas Fault in the Carrizo Plain. By Ikluft - Own work, GFDL, https://commons.wikimedia.org/w/index.php?curid=3106006

US map depicting earthquake loss by county
November 30, 2000

US map depicting earthquake loss by county

Figure 3-4

This map depicts annualized earthquake loss by county. The estimated losses consider the value of buildings in each specific area.

Map depicting difference in USGS estimates of earthquake hazards from 2002 and 2014
November 30, 2000

Map depicting difference in estimates of earthquake hazards 2002-2014

Figure 4-1

This map depicts the difference in USGS estimates of earthquake hazards across the nation in 2002 and 2014. The new FEMA earthquake loss report includes the 2014 data, while the previous 2008 report includes the 2002 data. The negative values represent a decrease in estimated hazard since 2002 and the positive values represent an increase.