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Good news for Californians: An earthquake early-warning system sounded off three seconds before a tremor shook Los Angeles County on Tuesday night.

SALT LAKE CITY — Good news for Californians: An earthquake early warning system sounded off three seconds before a tremor shook Los Angeles County Tuesday night.

The ShakeAlert system, which is still under development by the U.S. Geological Survey, had a successful run Tuesday night, registering a jolt of activity right before a tremor hit at 7:33 p.m. Tuesday, according to the San Francisco Chronicle.

Shaking from the earthquake was felt from Ventura County to Orange County.

Several aftershocks shook California following the earthquake, CBS Los Angeles reported.

The new system helps provide advance warning by detecting seismic waves right before the earthquakes hits, the Chronicle reported.

As the Fairfield Daily Republic reported, the new system is still under beta testing but more people are expected to test it out later this year.

“It works on a simple principle: The shaking from an earthquake travels at the speed of sound through rock — which is slower than the speed of today’s communications systems,” the Daily Republic reported.

In fact, the system could help people who live farther away from the earthquake.

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Since it would take about a minute for a 7.8-magnitude earthquake in San Andreas to reach Los Angeles, the “early-warning system would give L.A. residents crucial seconds, and perhaps even more than a minute, to prepare,” the Daily Republic reported.

The USGS has worked to develop an early-warning system for the West Coast for years. However, it has fallen short of funds.

Harvard and Google are also building a method to predict earthquake aftershocks. The researchers are using seismological data to figure out when aftershocks will hit, according to Engadget.