I saw on a map that I live in an area of "high liquefaction probability." What does that mean and can I do anything about it?

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Episode Number: 32

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Location Taken: US

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Welcome to CoreFacts, where we're always short on time and big on science. I'm Steve Sobieszczyk. Let's get right to it, today's question is:

I saw on a map that I live in an area of "high liquefaction probability." What does that mean and can I do anything about it?

A liquefaction hazard map typically predicts the approximate percentage of a certain area that will liquefy and show surface manifestations of liquefaction such as sand boils and ground cracking. Liquefaction takes place when loosely packed, water-logged sediments at or near the ground surface lose their strength in response to strong ground shaking. Liquefaction occurring beneath buildings and other structures can cause major damage during earthquakes. A liquefaction map depicts the hazard at a regional scale and should not be used for site-specific design and consideration. Subsurface conditions can vary abruptly and borings are required to address the hazard at a given location.

The actions one should take in an area subject to liquefaction depend on the use and occupants of the structure, the degree of hazard, the topographic setting, one's willingness to accept risk, and the degree to which the hazard is understood and quantified. If the three factors necessary for liquefaction (loose, granular sediment; high water table; and strong shaking) are thought to exist at a site, then obtaining the advice of an expert geologist or geotechnical engineer is recommended. Once the liquefaction hazard is identified and characterized, methods of mitigation can be considered. Mitigation is accomplished through a variety of approaches, including: (1) avoiding hazardous areas, (2) purchasing insurance to cover anticipated losses, (3) "improving" the ground so it is less susceptible to liquefaction and (4) fortifying structures to withstand liquefaction of underlying soils. More information check the links in our show notes: http://geomaps.wr.usgs.gov/sfgeo/liquefaction/

And now you know. Join us again every weekday for a new CoreFact. For other CoreFacts, or for CoreCast, our in-depth science podcast, go to usgs.gov/podcasts. We are accepting your science questions, so if you're curious about something that we can answer, send us an email at corefacts@usgs.gov or leave a voicemail at 703-648-5600, long distance fees apply.

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