A strong earthquake measuring 6.5 on the Richter scale struck off the coast of northern California this morning. The US Geological Survey reported said quake struck at about 4:27 p.m. local time and was centered about 33 miles from Eureka. The Police in Ferndale city reported some damage to the city hall building but gave no reports of injuries. The quake lasted for about 30 seconds and left much of Eureka without power.