Earthquakes usually occur along fracture zones in Earth's crust, where large tectonic plates slide past one another and become locked. Stress builds up over long periods and is suddenly released in the form of an earthquake.

SONOMA COUNTY, CA - A preliminary 2.0 magnitude quake shook close to The Geysers on Monday morning, the U.S. Geological Survey reported.

The mega-earthquake. It’s coming. We don’t know exactly when or how big it’s going to be, but it’s coming. It will be chaotic, and with millions of lives on the brink, California will be put to the ultimate test.

A series of moderate earthquakes rattled the waters off Northern California and southern Oregon early Thursday near the Mendocino Triple Junction.

At least two strong earthquakes struck off the Northern California and Oregon coasts early Wednesday, including a magnitude 5.7 quake. No Tsunami Warnings were issued.

The string of moderate earthquakes occurred within hours along a seismically active stretch near the California–Oregon border.