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Why Should I Prepare? -- Big Quakes Will Affect You

The Disastrous 1989 Loma Prieta Earthquake Was Not the "Big One"!

The Loma Prieta earthquake released only 3% of the energy of the Great 1906 quake. Although it occurred in the Santa Cruz Mountains, far from the Bay Area's urban centers, it caused destruction not only in nearby Santa Cruz and Watsonville but also in San Francisco and Oakland:

• More than 60 people died, most in the collapse of the Cypress freeway structure in Oakland.
  
  
• About 16,000 homes and apartment units were so badly damaged that they could no longer be lived in. The American Red Cross operated 45 shelters housing more than 6,000 people, many of them for several months.
  
  
• The San Francisco-Oakland Bay Bridge was closed for more than a month because a portion of its eastern span collapsed. This closure and the collapse of the Cypress Freeway were the most dramatic of 142 road closures in the Bay Area.
  
  
• Direct physical damage to buildings and structures totaled $6 billion; other related losses were an additional $4 billion (losses in 1989 dollars).

ShakeMap of the 1989 M 6.9 Loma Prieta Earthquake

This "ShakeMap" shows levels of shaking in the San Francisco Bay region during the1989 magnitude (M) 6.9 Loma Prieta earthquake. Shaking intensities are shown by colors corresponding to the "Modified Mercalli Intensity Scale," which uses Roman numerals and is based on actual reports of shaking and damage in earthquakes. ShakeMaps are now automatically generated from shaking measurements recorded by an extensive network of seismographic instruments operated by the partnership organizations in the California Integrated Seismic Network (CISN) (see page 30). CISN ShakeMaps are now available online within minutes after a significant earthquake at
http://earthquake.usgs.gov/shakemap/ or http://www.cisn.org/shakemap/

How Do I Find Out the Expected Shaking in My Neighborhood?

The Association of Bay Area Governments (ABAG) operates a Web site designed to provide this information in the form of earthquake-shaking hazard maps at http://quake.abag.ca.gov/. These maps show expected shaking intensities in the Bay Area for various earthquake scenarios, such as a quake on the Peninsula segment of the San Andreas Fault or the northern Hayward Fault. These maps can be "zoomed in" to display your neighborhood.

Other ABAG earthquake hazard maps show areas of liquefaction susceptibility, landslide hazards, potential fault ruptures, and tsunami inundation. ABAG even has maps for other natural hazards such as wildfires and flooding.

Some words of caution:

• Because these hazard maps are based on general information, they are reasonably accurate for a neighborhood, but much less accurate for a particular address.
  
  
• The maps in this booklet or on ABAG's Web site are based on probabilities, so actual earthquakes could produce different damage patterns.

Many Likely Earthquake Scenarios for the Bay Area Will Cause More Damage Than the Loma Prieta Earthquake...

What if the Hayward Fault in the East Bay ruptured from San Pablo Bay to Fremont in an earthquake of magnitude 6.9, like Loma Prieta?

If this scenario earthquake for the Hayward Fault occurs, areas of soft soils along the margins of San Francisco Bay, particularly in the East Bay, are likely to experience intense shaking and liquefaction. These areas are heavily urbanized and may have devastation similar to or greater than that of the area around the Cypress freeway structure in Oakland in 1989, shown here.

"Scenario" ShakeMap for a Possible M 6.9 Earthquake on the Hayward Fault

This "scenario" ShakeMap shows predicted levels of shaking in the San Francisco Bay region for a possible magnitude (M) 6.9 earthquake on the Hayward Fault. Such scenario maps are computer generated using information about the projected quake magnitude, distances from the rupturing fault, and local geologic conditions. Scenario ShakeMaps are available online at http://quake.usgs.gov/research/strongmotion/effects/shake/archive/scenario.html

Projected Consequences and Implications for the Bay Area from a Magnitude 6.9 Earthquake on the Hayward Fault

Your Life Could Change Unexpectedly in the Next Quake. Consider...

Where will your family be?

• Your children may be at school, day care, or other activities.
  
  
• Family members may be at work or commuting.
  
  
• Pets may run away or be injured.

After the 2001 magnitude 6.8 Nisqually earthquake, this school in the Puget Sound area of Washington was closed for repair.