 The 1992 Cape Mendocino earthquakes ( or 1992 Petrolia earthquakes ) occurred along the Lost Coast of Northern California on April 25 and 26 . The three largest events were the M7.2 thrust mainshock that struck near the unincorporated community of Petrolia midday on April 25 and two primary strike @-@ slip aftershocks measuring 6 @.@ 5 and 6 @.@ 6 that followed early the next morning . The sequence encompassed both interplate and intraplate activity that was associated with the Mendocino Triple Junction , a complex system of three major faults ( including the Cascadia subduction zone , San Andreas Fault , and Mendocino Fracture Zone ) that converge near Cape Mendocino . The total number of aftershocks that followed the events exceeded 2 @,@ 000 . 
