Geology professor corrects fault-zone assertion following earthquake

Todd Greene says Lake Almanor shake took place on active fault line

CHICO >> Prof. Todd Greene, chairman of Chico State University’s Department of Earth and Environmental Sciences, said Tuesday he made an error and wants to correct it.

An earthquake measuring 5.5 magnitude jolted the Lake Almanor area in Plumas County at 4:19 p.m. May 10. During a Friday, May 11 interview, Greene said there are two fault zones near and under Lake Almanor — but that neither had been active “during the past 15,000 years.”

However, Greene researched the topic during the following days and determined that there had indeed been activity on the fault.

“I did some more digging and it turns out there is an older reference — 1995 — that indeed shows active faults running through Lake Almanor,” the professor said. “The U.S. Geological Survey site that I was using before just wasn’t updated to show this. In other words, these recent earthquakes occurred along known active faults.

“I’m not sure why the USGS site wasn’t updated,” he said.

He referred to a book titled Quaternary Geology Along the Boundary Between the Modoc Plateau, Southern Cascade Mountains, and the Northern Sierra Nevada by Friends of the Pleistocene. The book resulted from a 1995 Pacific Cell Field Trip, with Bill Page as trip leader and Jeff Unruh creating the map and conducting the discussion.

The May 10 shake generated 28 aftershocks in and around Lake Almanor, including a 5.2-magnitude temblor at 3:18 a.m. the following day. Things quieted down after the series, however, with five very small aftershocks beginning Sunday, according to the USGS website. A sixth, which occurred early Tuesday morning, checked in at 3.1 magnitude.