A Comparison of Two Bay Area Earthquakes: 1989 v. 1906
Comparing Shaking Intensity from Two Bay Area Earthquakes:
The 1989 Loma Prieta earthquake and the 1906 San Francisco earthquake
About this page
The 1989 Loma Prieta earthquake caused billions of dollars in damage and claimed more than sixty lives. But was it "the big one"? Take a look at the comparison between the images below and decide for yourself.
A Lesson Plan for using these images in your classroom is free online from DLESE.
The colors on the map indicate Modified Mercalli Shaking Intensity at each point, which is often (but not always) written as Roman numerals to avoid confusion with earthquake magnitudes. The "Instrumental Intensity" indicated in the Bay Area images is determined by a slightly different technique, but is designed to be virtually identical to the traditional Modified Mercalli scale. More information about shaking intensity:
The data about the 1906 earthquake come from USGS Open File 2005-1135, painstakingly compiled from historical records by John Boatwright and Howard Bundock. Their official report is available online. The data from 1989 are from the USGS "Did you Feel It" Community Intensity Project and instrumental recordings.
Want a closer look?
Click to enlarge images.
Bay Area View
More maps are available directly from the USGS Open File Report.
HOW LONG WAS THE RUPTURE?
HOW STRONG WAS THE SHAKING?