The powerful Mojave Desert earthquakes that rocked California ended a years-long lull in major seismic activity and raised new interest in an early warning system being developed for the West Coast.

The ShakeAlert system is substantially built in California and overall is about 55% complete, with much of the remaining installation of seismic sensor stations to be done in the Pacific Northwest, said Robert de Groot of the U.S. Geological Survey.

Areas that have the appropriate number of sensors include Southern California, San Francisco Bay Area and the Seattle-Tacoma region, de Groot said.

The system does not predict earthquakes. Rather, it detects that an earthquake is occurring, rapidly calculates expected intensity levels and sends out alerts that may give warnings ranging from several seconds to perhaps a minute before potentially damaging shaking hits locations away from the epicenter.

Depending on the distance, that could be enough time to automatically slow trains, stop industrial machines, start generators, pull a surgical knife away from a patient or tell students to put the “drop, cover and hold” drill into action.

For alerts to be useful, delivery has to be timely, and that’s a problem with current cellphone technology. For cellphone delivery, the USGS ultimately intends to use the same system that delivers Amber Alerts, sending signals to everyone in reach of cellphone towers in defined areas where damaging shaking is expected.

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