Earthquake Alerts Are A Big Deal

This is amazing. Google earthquake alerts reached 11.4 million people seconds to two minutes before two of the strongest quakes in the country’s history. How?

"The trick is the accelerometer inside almost every smartphone. The same chip that rotates your screen can feel the faint tremor of a seismic wave. Google taps more than two billion of them worldwide.

A quake sends out two kinds of wave. Fast primary waves arrive first and do little harm. Slower secondary waves follow, and they cause most of the shaking. The gap between them is the warning window."