A page reporting a 5.9 earthquake near Carson City, Nev., was taken down by USGS on Dec. 4.
USGSA false alert that warned of a 5.9 magnitude earthquake that didn’t happen was triggered after multiple sensors in Nevada detected movement Thursday morning, according to U.S. Geological Survey officials.
Robert DeGroot, operations team lead for the USGS-managed ShakeAlert Earthquake Early Warning System, told SFGATE that at least four sensors across Nevada detected motion, leading to an automated warning sent out via MyShake Alert to a large portion of California.
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“We don’t have an explanation for why the ground shook,” DeGroot told SFGATE by phone Friday. “Something happened in the ground because the sensors detected motion. So that part is completely unknown at the moment, but we know that the sensors were triggered.”
DeGroot said after the sensors picked up motion the information was automatically moved to a processing center that made the determination that a magnitude 5.9 earthquake had occurred.
“It did exactly what it was supposed to do, and then that information is passed on to the people who deliver the alerts for us,” he explained.
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That warning, issued shortly after 8 a.m. on Thursday, was sent to wide swaths of California including the “Bay Area, the Eastern Sierra, and parts of South-Central California,” according to an email from USGS. Shortly after the warning was sent, USGS duty officers realized no earthquake had been detected and removed the earthquake information from the USGS page.
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USGS is investigating an “errant” report of an earthquake with a preliminary magnitude of 5.9 near the Lake Tahoe region on Thursday, Dec. 4.
USGSThere are over 1,600 sensors across multiple western states aimed at detecting earthquakes. The sensors in the area in Nevada where the quake was detected are on average about 10 to 20 miles apart, DeGroot said.
“We have always thought about the possibility of something like this happening, and so we built in lots of safeguards,” DeGroot explained. The safeguards include a minimum of four stations needing to detect the same motion to confirm a quake.
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An investigation is ongoing into what could have tripped the sensors in the region even when they are miles apart. DeGroot said one silver lining of the false alert is that they will be able to fine-tune the algorithm used to determine an earthquake has occurred.
“Knowing how this happened, you can actually improve the software,” he said.
