At about 4:30 pm local time a large strike-slip earthquake of magnitude 6.5 occurred about 40 kilometers west (that is, offshore) of Eureka, northern California. It's near the Mendocino triple junction, which the focal mechanism seems to tie it to. Strong shaking has been reported in Eureka and nearby areas. This is the biggest event in the lower 48 states in quite a while (a 7.2/6.6 pair struck 200 km offshore in the same area on 15/17 Jun 2005) and the first magnitude-6 event since the 6.0 Wells Nevada quake on 21 Feb 2008. Details on the US Geological Survey's special page for the event
The biggest earthquakes on land (not offshore) in the lower 48 in the last 10 years are four:
Nisqually, Washington, 28 February 2001 (M6.8)
- San Simeon, California, 22 December 2003 (6.5)
- Parkfield, California, 28 September 2004 (6.0)
- Wells, Nevada, 21 February 2008 (6.0)
The 1990s were much worse.