It’s been 110 years since the great quake of 1906 destroyed San Francisco. Ever since, San Francisco, and California as a whole, has obtained a reputation for these ground-shaking natural disasters. On the anniversary, we thought we’d take a look at every significant California earthquake since 1900 and see just how many are in San Francisco.
For starters, we used our new Advanced Tools to look at a heat map of the data. This takes into account the concentration of individual quakes. The greater Bay Area is certainly a hot zone, though that is a geographically large region. To the North is Santa Rosa, with Santa Cruz to the South. Each of these cities is around 50 miles away from San Francisco.
Next we added a record to the top of our data to serve as the center of San Francisco. Then we had BatchGeo calculate the distance from every earthquake epicenter to that San Francisco data point. With the map below, we can now see how many earthquakes have been near San Francisco.
View California Earthquakes Relative to San Francisco in a full screen map
Using BatchGeo’s grouping feature, we can filter the map to see the earthquakes within about 50 miles of San Francisco. There have only been half a dozen since 1906, and no others that were centered within the city. The closest was a 2014 Napa quake, 30 miles away with a magnitude of 6.
Distance is only one factor. Plate tectonics and magnitude have a lot to say about how far the disastrous effects will travel. The 1989 earthquake that interrupted the Bay Bridge World Series between the Oakland A’s and San Francisco Giants collapsed a section of that bridge, as well as a San Francisco freeway. The epicenter was nearly 60 miles away from San Francisco in the Santa Cruz Mountains.
Expanding the radius to 100 miles still only shows 13 major earthquakes, including both 1906 and 1989, as well as others that did no damage in San Francisco. That leaves another 41 earthquakes elsewhere in California. There are several clustered around Eureka, a small group in the Sierras, and quite a few in the Los Angeles area.
To conclude, in San Francisco you can expect an earthquake every decade or so, but it’s unlikely to match the expectations set by disaster movie San Andreas, the devastation of 1906, or even the World Series postponing shakes of 1989.