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why is san francisco at risk from earthquakes

How Likely is Liquefaction to Happen near Me? This Google Earth file shows a map of the distribution of deposits in the Bay Area most likely to liquefy during the next big earthquake. Liquefaction occurs when young, sandy, water-saturated deposits are shaken strongly during earthquakes. When this occurs, these deposits lose their strength and behave like a liquid, quicksand. Buildings and other structures can be damaged when their foundations sink into these soupy sands. Geologists determine the potential for liquefaction by mapping young, sandy deposits that are likely to contain water. This Liquefaction Susceptibility layer is intended solely as an educational tool.

produces state-mandated regulatory maps that show Zones of Required Investigation for liquefaction (and landslide) hazard. These state maps depict zones where site specific studies are required for new construction. These zone maps also are used in real estate transactions sellers of properties within a "Zone of Required Investigation" must disclose that fact to prospective buyers. Using newly collected data and evolving theories of earthquake occurrence, U. S. Geological Survey and other scientists now conclude that there is a 63% probability of at least one magnitude 6. 7 or greater quake, capable of causing widespread damage, striking somewhere in the San Francisco Bay region in the next 30 years.

Such an earthquake is most likely to occur on one of seven main fault systems. The earthquake probability is highest for the Hayward-Rodgers Creek Fault system, 31%, or nearly 1 out of 3. Understanding Earthquake Hazards in the Bay Area The Association of Bay Area Governments (ABAG) estimates that after an earthquake a potential housing loss to Bay Area communities of over 159,000 units. This would have disastrous effects on our local and regional economies.

It also means that recovery, repair and rebuilding time for every household will be very lengthy, due to the number of homes that will need repairs or replacement. Households that are less damaged will certainly make much faster recoveries. The cost of earthquake insurance has increased dramatically. At the same time, benefits have decreased. Many homeowners have made a conscious choice to accept the earthquake risk personally by declining earthquake coverage. Governmental resources to help with damage recovery, especially at the personal level, are declining. All these factors, together, make it even more critical to focus on the prevention of earthquake-related damages.

Based on extensive post-earthquake evaluations, experts agree that structural damage can be greatly reduced by following recommended practices of seismic retrofitting. Retrofitting will reduce the cost of repair, and may even prevent structural damage altogether. The benefits go well beyond being simply financial. It will make your home safer and help to keep it habitable following a major disaster. It will also reduce the amount of time and effort needed for recovery, returning your family much more quickly back to your normal life style.

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