What your smartphone tells UC Berkeley researchers about Bay Area earthquakes

What your smartphone tells UC Berkeley researchers about Bay Area earthquakes

For about seven seconds on a Tuesday morning in October, a magnitude 5.1 earthquake occurred Calaveras Fault tore Near San Jose – causing parked cars to oscillate, high-pitched rocking back and forth and alerts from 100,000 cell phones.

For many residents, the Seven Trees earthquake was a terrifying omen, foreshadowing the giant earthquake that could strike the Bay Area at any moment: the odds of a “major earthquake”—an earthquake of at least magnitude 6.7—are two in three within the next 30 years. , according to scientists at the US Geological Survey.

But for experts at UC Berkeley, the October earthquake has become a sprawling research project in which thousands of individual smartphones acted as seismic instruments. These phones are equipped with MyShake app That records the movement of the Earth when the phone is connected and stationary, is generating data that has changed scientists’ understanding of earthquakes, and rendering Much clearer picture How people experience it in a home, classroom, or on the 18th floor of San Jose City Hall.

Six hundred telephones across the Bay Area recorded waveforms from the Seven Trees earthquake and uploaded the data to Berkeley Seismological Laboratory. The researchers who collect and analyze these recordings are making new observations from dozens of earthquakes that have rocked the Pacific Northwest since 2016, the year they launched the MyShake app.

Biggest benefit yet: Buildings amplify earthquake motion by three times. When seismologists at Berkeley analyzed reports from smartphones, they found that the phones’ accelerometers recorded ground motion at three times the amplitude of conventional sensors dug into the ground, or placed on rocky outcrops.

A person checks the “MyShake” app on his smartphone in Hollywood on October 17, 2019. – California on Thursday launched the country’s first earthquake warning system with the hopes that residents will be alerted within seconds of a possible impending disaster and they can “get down, cover and keep going.” put it.” (Photo by Chris Delmas/AFP) (Photo by Chris Delmas/AFP via Getty Images)

Chris Delmas, Contributor/AFP via Getty Images

“This is really interesting,” said Richard Allen, director of the Seismological Laboratory and leader of the team that developed the app. “Because the phone is on your desk or bedside table. It registers the same ground shaking that we are actually experiencing.”

This may explain why the relatively modest South Bay earthquake sparked so much fear, and such a buzz on Twitter, even though it caused no damage. A person standing inside a home or office may feel three times more vibration and wobble than someone standing outdoors.

Beth Pleasants, a resident of the Japantown neighborhood of San Jose, said the lights above her kitchen table started to flicker back and forth when the quake started. The noise activated the pet’s camera, which sent video footage to Pleasants’ phone.

“It was wild,” Pleasants said, recalling the moment she and thousands of other Bay Area residents felt the earth pounding, at 11:42 a.m. on Oct. 25. The peasants were sitting in her parked car when she began to sway, as if she said someone was pushing on the bumper. Through the windows, I glimpsed the shaking telephone poles outside.

Allen said the magnitude of the Seven Trees earthquake made it a compelling test case for the MyShake alert system, as it distributed alerts to smartphone users across the Bay Area.

San Francisco residents, who were on the edge of the alert area, received warnings about 18 seconds before the roar began. People in San Jose received less notice, and those close to the epicenter may have received alerts as soon as the ground began to convulse.

Alex Guichet said he received “about a second of warning” from the MyShake app in his Palo Alto office, where the cramps were relatively benign. Ninety miles away, Associate Professor Ryan Patterson was teaching the geosciences lab at Modesto Junior College, when he heard the cacophony of alarms from his students’ phones.

“I told everyone to fall and cover and hold on,” Patterson said, remembering how most of his students hunched under tables and desks, even though they never felt the tremors. People in classrooms on the second floor and down the hall “felt it a little bit,” Patterson said, an indication of the reach of the quake.

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