More faults found off West Coast.

• Position: Earthquakes

Five times more mapped faults than previously imaged by scientists apparently cross the fractured Gorda Plate about 125 miles off the Northern California and southern Oregon coasts, according to an Oregon State University, Corvallis, study. More than 340 strike-slip and spreading-center related normal faults or fault segments were found in the region, says Jason Chaytor, a master's candidate in the College of Oceanic and Atmospheric Sciences.

Researchers once had plotted more than 60 faults spilling out across the Gorda Plate from the Gorda Ridge spreading zone, he points out. However, analysis of data collected in 1997 imaged more suspected faults. Using multibeam bathymetry, sidescan sonar, and seismic reflection data that provide soundings of water depth and echo strength, seafloor imaging pro grams can interpret depths and echo strengths and allow scientists to create a snapshot of the seafloor. "Long linear features strongly suggest the faults are more pervasive throughout the Gorda Plate than originally thought," Chaytor indicates. "A lot of the faults are actually created at the spreading ridge--the Gorda Ridge spreading zone. This isn't unusual. It's quite common to see this many faults in these areas."

The Pacific Coast from northern British Columbia to Punta Gorda, near Cape Mendocino in California's Humboldt County, is the region known to...