This system doesn’t predict earthquakes, and after quake’s early this year failed to produce a notification on phones in Los Angeles, the threshold for a warning has been lowered to at least a magnitude 4.5 and Modified Mercalli Intensity (MMI) of 3, which is similar to a truck driving by outside your house. According to UC Berkeley, tests have shown alerts can reach users of the MyShake app in about 3.7 seconds, while the WEA (like severe weather notifications and Amber Alerts) had an average delivery time of 13 seconds — so probably go ahead and install that app.
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