Team to Map the San Andreas Fault

Ohio State University researchers using a new laser-imaging technique hope to draw new maps of the San Andreas fault that could help scientists better predict earthquakes in California. The image resolution on existing maps of the fault show post-quake earth movement of about 30 feet.

The Ohio State team directed by geophysicist Mike Bevis is working with data from a light plane equipped with a new type of laser-mapping system that can show detail down to a couple of inches.

The twin-engine Cessna makes low, slow passes over the fault with equipment that shoots 70,000 laser pulses per second at the ground, then registers the light beams when they bounce back, like radar.

Ground personnel assist with global-positioning devices.

"It gives a much sharper picture of the topography. For many of the features we look at from earthquakes, the (terrain) displacement of the last quake can make predictions about the next quake," said Ray Weldon, a University of Oregon geologist.

The payoff will come after another substantial quake — possibly the oft-discussed "big one" — when researchers can make another sweep with the Cessna to measure the movement, said Ken Hudnut, a geophysicist with the U.S. Geological Survey and a member of the study team.

No one on the team, though, wishes for a catastrophic quake.

"The physics of frictional slippage are fundamentally chaotic. That's why earthquake prediction is so hard. In order to fully consummate our experiment, we do need a 'big one,'" Hudnut said.

Bevis' team will spend the next year working with the data to produce new maps of the southern stretch of the fault. The work is funded by a $500,000 National Science Foundation grant.