Comparing Shaking Intensity from Two Bay Area Earthquakes

Science Center Objects

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 for the 1989 Loma Prieta and the 1906 San Francisco earthquakes, and decide for yourself.

The colors on the map indicate Modified Mercalli Shaking Intensity (MMI) at each point, which is usually (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.

State-Wide View

before
after
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Comparison between  the 1989 Loma Prieta and the 1906 San Francisco earthquakes.

MMI ShakeOut Maps

before
after
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MMI ShakeMaps for the 1906 and the 1989 earthquakes.

How long was the rupture?

Comparison of rupture length of 1906 and 1989 earthquakes

Comparison between the length of the rupture of the 1906 and 1989 Loma Prieta earthquakes. (Public domain.)

How strong was the shaking?

Comparison of 1989 and 1906 earthquake records

Comparison of 1906 and 1989 records at Gottingen, Germany. (Public domain.)

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