"It looks like it is on the San Jacinto fault system in Borrego Springs, or a splinter of it," said Bob Dollar, a seismologist at the USGS. "A lot of scientists are working on this fault because it is the most active fault in Southern California. We've had more 6s there than any other fault in Southern California in the last century."
Rockwell said, "Today's quake was on the Coyote Creek strand of the San Jacinto, near the Anza seismicity gap. When the San Jacinto has quakes that rupture the surface, they tend to be in the 7.2. to 7.3 range. But the system also gets a lot of quakes in the 5.0 to 6.0 range that don't break the surface."
Cal Fire reported damage from the quake on Old Highway 80 near Buckman Springs Road in Campo.
Because of the shaking, a large boulder fell from a cliff, hitting the highway and leaving a 3-foot-wide by 1-foot-deep hole, said Cal Fire Battalion Chief Nick Schuler. The boulder's fall also broke two mature oak trees, Schuler said.
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