The Bay Bridge in San Francisco didn't fare too well during the earthquake of 1989, when a portion of its upper deck collapsed onto the lower deck. A building in downtown San Francisco damaged in the 1906 quake. Damage to a garage in the North Beach area, near Embarcadero. Damage on East Howard Street after the 1906 earthquake.

Geology of San Francisco San Francisco is situated on the central west coast of California, in the San Francisco Bay Area. It is basically an island, connected to the rest of the Bay Area by bridges such as the Golden Gate and Bay Bridge. San Francisco is built mainly on bayfill, although some apartment buildings on hills (such as Nobb Hill) have foundations on bedrock. This rupture occurred during the 1906 San Francisco earthquake along the San Andreas fault at Point Reyes. The offset near this point was 21 feet. The city is situated near many active faults. The San Andreas, Hayward, and San Gregorio faults all lie in the Bay region, to name a few. The Hayward fault caused an earthquake in 1868 in San Francisco, dubbed the "Great San Francisco Earthquake" prior to 1906's infamous quake. The 1906 quake was the result of shifting along the San Andreas. More recently, the 1989 Loma Prieta quake also occurred on the San Andreas, though not nearly as widespread as the 1906 quake. In the next 30 years, there exists a 70% chance that a major earthquake (magnitude 6.7 or higher) will strike the Bay Area. The highest probabilities for an earthquake are the Rodgers Creek (32%), Hayward (21%), and Calaveras (18%) faults, though an earthquake can occur at any time or place. Because of these factors, it is imperitive to protect yourself and your family from potential earthquakes. From past experience, we can conclude that the best building during an earthquake has a wood frame and is built on bedrock. A concrete building has a higher probability of collapse and more potential to produce serious injury. A foundation consisting of bayfill or sand would result in a serious liquefaction problem. But only having the right building won't necessarily protect you during--or even after--an earthquake. You need to know what to do in any case, whether you're at home, at work, or at school. Continue to the next page to learn how to prepare for an earthquake. --by Alex Hoff �

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