In 1906, only 650,000 people lived in the Bay Area. The 1906 earthquake left 225,000 of San Francisco’s 400,000 citizens homeless. At the time of the earthquake, much of the Bay Area was sparsely populated; San Jose was a small town of 25,000. Today, the Bay Area population has increased ten-fold to 7 million people, all at risk from expected earthquakes on one or more of the Bay Area faults. 2 million people, for example live on or close to the Hayward fault, which has among the highest probability of producing a magnitude 6.7 or greater earthquake in the next 30 years. The map shows the past and present population densities.
Urban Areas (127 kB)
In 2003, earthquake scientists led by the USGS estimated that there is a 62% probability of a magnitude 6.7 or greater earthquake in the Bay Area in the next 30 years. Some faults are more likely to rupture than others. The two most hazardous faults in the region are the Hayward-Rodgers Creek fault system (27%) and the San Andreas fault (21%). The East Bay has a higher earthquake hazard than the San Francisco peninsula due to the higher number of faults that traverse the East Bay. Which fault is closest to your house? What probability for a magnitude 6.7 or greater earthquake in the next 30 years have scientists assigned to it? For a detailed explanation visit the 2003 Earthquake Probability study.
Earthquake Probabilities for the Bay Area(132 kB)
Liquefaction occurs when young, sandy, water-saturated deposits are shaken strongly during earthquakes. When this occurs, these deposits lose their load-bearing strength and behave like a liquid. Buildings and other structures can be damaged when their foundations sink into these soupy sands. Geologists map the potential for liquefaction by mapping young, sandy deposits that are likely to contain water. The following map shows the distribution of deposits in San Francisco most likely to suffer liquefaction during the next big earthquake in the Bay Area. Detailed maps showing liquefaction susceptibility in other regions of the Bay Area are also available.
Liquefaction Susceptibility in San Francisco (89 kB)
To find out what you and your family should do to prepare, and to learn more about earthquake hazards in your community and neighborhood, please see these additional Earthquake Hazard Resources.