A shake alert went out over the U.S. Geological Survey's early warning system on Dec. 4, warning that a 5.9 earthquake near Carson City in western Nevada could produce heavy shaking in the region. But moments later, the survey announced the alert, which was sent to people as far west as San Francisco, was a false alarm.

A series of small earthquakes struck the San Ramon area early on Monday, the latest in a recent sequence of tremors affecting the East Bay, according to the US Geological Survey (USGS). A magnitude 2.

In the latest report prepared by a Japanese government earthquake task force, it was estimated that up to 298,000 people could be killed in a Nankai Trough megaquake with a magnitude of 8-9. The casualties would include 215,000 deaths caused by tsunami waves, the report said.