What does this map represent?5>
This map shows likely shaking intensity in the Bay Area in any 50 year period from all possible faults. It is an equivalent risk to a 500 year flood event. 10% in 50 years was chosen as it most closely aligns to the levels of shaking the current building code are designed to withstand. This intensity map is not intended to be site-specific. Rather, it depicts the general risk within neighborhoods and the relative risk from community to community.
How do I use this map to better understand my risk?
Determine which MMI zone your home is in (a closeup map is available on your county webpage). The darker the color and the higher the MMI, the greater ground shaking and potential damage your home is likely to experience in an earthquake. In fact, your home has a 10% chance of experiencing that level of intensity in any 50-year period. If you are in an area of higher MMI, you should seriously consider taking steps to retrofit your home.
Help! I’m a homeowner in the darkest zone. What do I do?
There are plenty of resources designed to help homeowners keep their homes safe. Visit our Homeowners page for help.
How was this map developed?
This map was developed in conjunction with USGS and CGS by determining PSHA for Peak Ground Velocity (PGV) for 52,961 points along a grid covering the entire Bay Area, at intervals of 0.05 degrees longitude and 0.05 degrees latitude. PGV was then converted to the Modified Mercalli Intensity (MMI) measure. This analysis incorporates soil conditions which affect the velocity of ground shaking.
This map was developed by ABAG and the Earthquake Mapping Update Advisory Committee meeting and generously funded by a grant from the USGS Earthquake Hazards Program.