Strong Earthquake Shakes Northern California
Map of earthquake location today (Mar. 10, 2014) near northern California.
Credit: USGS.

An earthquake of preliminary magnitude 6.9 struck last night off the coast of Northern California, according to the U.S. Geological Survey (USGS).

Shaking was felt across the region as far south as the San Francisco Bay Area and as far north as Eugene, Ore. There were no immediate reports of damage and no tsunami warnings were issued, the Associated Press reports.

The temblor's epicenter was 50 miles (80 kilometers) west of Eureka, Calif. It originated 10.3 miles (16.6 km) deep and struck at 10:18 p.m. Sunday local time (5:18 a.m. Monday UTC), according to the USGS.

Earthquakes of this size are considered major and can cause significant damage, especially with poorly built structures. Even well designed buildings can be damaged or, in some cases, destroyed depending on the severity of the quake and a building’s proximity to the epicenter. Earthquakes of this size are sometimes followed by significant aftershocks.

But the damage caused by any single event depends on the quake's depth, proximity to populated areas, building standards in the region, as well as the type of earthquake. The USGS frequently updates the magnitude of an event after more data is analyzed.

An earthquake's magnitude is a measure of the energy released at the source. It is just one predictor of the shaking that may ensue, which is affected by local and regional geology. Scientists know in a general sense what causes earthquakes but are unable to predict specific quakes.

This article will be updated if significant additional information becomes available. Find more earthquake news here.