Researchers drop seismic sensors off SoCal coast

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Starting this month, scientists with the Scripps Institution of Oceanography will drop seismometers on a stretch of ocean floor called the San Diego Trough. 

It’s a fault more than 90 miles long that stretches as far north as Catalina Island. 

Five seismometers will be deployed for three months focusing on the northern section of the fault.

Monica Kohler examines an ocean bottom seismometer sensor for evidence of seafloor mud conditions during a 2011 research trip to pick up ocean bottom seismometers deployed a year earlier.
Monica Kohler examines an ocean bottom seismometer sensor for evidence of seafloor mud conditions during a 2011 research trip to pick up ocean bottom seismometers deployed a year earlier. Monica Kohler/Caltech

Scripps seismologist Gabi Laske told KPCC that the research will help assess the hazard potential of offshore faults and how active they are by tracking earthquakes.

“They can be very, very small - magnitude one, one-and-a-half, that you don’t see with the current equipment that we have on land," she said. 

Laske hopes the project is a stepping stone for more research into areas like the Newport-Inglewood fault, which starts in Culver City and continues offshore. 

In a conversation with KPCC in March, UC Riverside's Robert Leeper said that a large earthquake on the Newport-Inglewood fault would produce heavy shaking from San Diego to Beverly Hills. 

Scripps previously placed seismometers around the San Diego Trough in 2015 as part of a $1.5 million pilot project to provide real-time access to data collected on the ocean floor.

Here's an example of a seismometer deployed and retrieved off the ocean floor. 

https://www.youtube.com/watch?v=njRQ1wO219g

Other projects have looked at seismic activity in underwater faults in Southern California. Monica Kohler researches earthquake engineering at Caltech. In 2010 her team dropped seismometers about 300 miles offshore. 

Kohler's research explored how underwater plate motion affected the fault system as well as the  shaking potential onshore from offshore earthquakes.

While research has typically focused on monitoring faults on land like the San Andreas Fault, she told KPCC that underwater faults can be just as active as the ones on land. 

“A large earthquake on any one of these offshore faults in the continental shelf region could cause very strong ground shaking in the coastal areas along any coast of Southern California,” Kohler said.

Both scientists say more extensive research into underwater faults is limited by a lack of funding. Laske's team recently submitted a proposal to the National Science Foundation that was denied.

A wave glider is deployed offshore during a Scripps pilot project in 2013 to see if the instrument could replace expensive ocean cables or a mooring to provide real-time data access to scientists onshore.
A wave glider is deployed offshore during a Scripps pilot project in 2013 to see if the instrument could replace expensive ocean cables or a mooring to provide real-time data access to scientists onshore. Gabi Laske/Scripps

She had hoped to fund a wave glider fitted with a communications device that would circle around ocean-floor seismometers and relay real-time seismic data to stations onshore. 

 

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