Study by Pasadena Geologists May Provide Proof California Long Overdue for The Big One

Published : Thursday, April 18, 2019 | 4:41 AM

USGS geologists Glenn Biasi and Katherine Scharer have analyzed previously published paleoseismic records from 12 locations along the San Andreas, San Jacinto, and Hayward Faults showing an unprecedented, 100-year absence of major earthquakes over the last millennium.

A new seismic study by two Pasadena-based U.S. Geological Survey geophysicists confirms that the last century’s hiatus from major California earthquakes on any one of the state’s three most infamous faults is unprecedented over the past 1,000 years.

What’s it mean?  Some think it signals a buildup of pressure precipitating The Big One.

No one knows why bigger earthquakes along the San Andreas, San Jacinto, and Hayward Faults stopped happening, but it is eerily unusual.

The researchers,  Glenn Biasi and Katherine Scharer, calculate that such a hiatus is extremely unlikely, with only a 0.3% chance of being a fluke.

“Statistically speaking, this outcome is highly improbable,” Biasi told Earth & Space Science News. “It suggests that there must be some Earth system properties at work that we don’t fully understand yet.”

The co-authors analyzed previously published paleoseismic records from 12 locations along the three major faults.

According to additional USGS data, there is a 60 percent chance there will be a “strong” event in Los Angeles in the next 30 years. There’s a 60 percent chance an earthquake measuring magnitude 6.7 will hit in the area, there’s a 46 percent chance it will be an earthquake measuring magnitude 7 and there’s a 31 percent chance the earthquake could measure magnitude 7.5.

Retired seismologist Lucy Jones said there is no doubt a large earthquake is on the not too distant horizon

“This will happen,” she said. “We are not stopping plate tectonics. Just give it enough time.”

Biasi and Scharer’s paper is based on the work of Ned Field, a former Pasadena-based scientist.

No one can predict how or when a major earthquake can strike and scientists agree to disagree on what the latest findings may represent.

Biasi said there is a likelihood of increased earthquake activity but it’s difficult to tell to what degree.

“In terms of a period of heightened activity it would not be a scientific surprise,” Biasi said. “I personally would expect it.”

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