The May , 2 2010 Pichilemu earthquake was a magnitude 6.0 MW earthquake that struck off Pichilemu , Chile , at 10:52 AM on May 2 , 2010 at the epicenter , at a depth of 31 k. USGS described that the epicenter was 70 k south-southwest of San Antonio , 105 k west Regional capital of Rancagua , 105 k northwest of CuricÃ and 140 k southwest of the Chilean capital of Santiago . The 2 May 2010 Pichilemu aftershock was a magnitude 5.8 MW earthquake that struck O'Higgins , Chile , at 10:52 a.m. on 2 May 2010 at the epicenter , at a depth of 32.9 k and epicenter 12 k northwest of Pichilemu , according to the University of Chile Geological Service .