text: what was the richter scale of the california earthquake in 1906?   the 1906 san francisco earthquake was a major earthquake that struck san francisco and the coast of northern california at 5:12am on wednesday, april 18, 1906. the most widely accepted magnitude for the earthquake is a moment magnitude (mw) 7.8; however, other values have been proposed from 7.7 to as high as 8.3.[1] the mainshock epicenter occurred offshore about 2 miles (3 km) from the city. it ruptured along the san andreas fault both northward and southward for a total length of 296 miles (477 km).[2] shaking was felt from oregon to los angeles, and inland as far as central nevada. the earthquake and resulting fire would be remembered as one of the worst natural disasters in the history of the united states.