High Quality Content by WIKIPEDIA articles! The 2010 Eureka earthquake occurred on January 9, 2010 at 4:27:38 p.m. PST offshore of Humboldt County, California, United States. The magnitude was measured as 6.5 Mw, and its epicenter was located offshore in the Pacific Ocean 33 miles (53 km) west of the nearest major city, Eureka. Additionally, there was a separate earthquake further offshore of Eureka on February 4, its magnitude was slightly less, at 5.9. It was also the most significant earthquake in the Eureka area in terms of magnitude since an earthquake in 1992. It was the largest earthquake in California in over a decade, since the Hector Mine Earthquake (7.1) of 1999.