Earthquakes
Plain guides to official alerts: what the levels mean, who issues them, and where to find the original. Official warnings and local authorities always come first.
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Earthquakes
Earthquake magnitude vs. intensity, and why “felt” differs from “recorded”
Magnitude measures an earthquake’s size; intensity describes shaking in one place. How USGS magnitude, Mercalli and JMA shindo differ, in plain words.
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Regional guides · Earthquakes
Earthquake alerts in California
How earthquake early warning and earthquake reports work in California, from ShakeAlert, MyShake and phone alerts to USGS, and what each can do.