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Dec 11, 2005

New 3-D Map May Help Predict Earthquakes

In a pioneering effort to show why earthquakes devastate some areas, yet leave other areas almost untouched, a team of scientists have completed a computerized three-dimensional map of the upper 20 miles of the Earth's surface beneath the San Francisco Bay Area. The map, which was a joint effort of the U.S. Geological Survey and the California Geological Survey shows what happened during the Loma Prieta quake of 1989.

The 3-D maps allow researchers to look at digital "slices" of the area at any point they choose. Each slice shows the earth's surface and rock layers to a depth of 20 miles. Different colors designate different layers of rock, hard, dense formations are darker colors; younger, less compact, formations are depicted in lighter shades.

The San Mateo County Times details more on how the maps were made:
The new maps use sub-surface information from many sources, Brocher said. Geologists have been gathering information for 100 years. "There have been lots of bore holes for water wells. There even was some oil industry drilling in the 1960s and 1970s.

"It's not widely known, but there was a big natural gas field developed near Antioch around World War I," he said. "Bay Area-wide we found over 100 bore holes and they go down as deep as three miles."

Earthquake researchers are excited about the new map and its potential to help predict earthquakes or at least help minimize their destruction. Richard Allen, with the University of California, Berkeley told the Times, "This should allow us to make better predictions. This 3-D map gives us more of a continuous picture of what the substructure of the Earth looks like. When we understand what kind of velocity we can expect, then we can predict how much ground shaking there will be."

Researchers plan to input seismic information from the Loma Prieta quake into the new 3-D model and see how well it predicts ground shaking, compared to known impacts.

The map as well as links to some 3-D versions are here.