A magnitude-5.1 earthquake struck the Los Angeles area Friday night , jolting nearby communities and breaking water mains in some neighborhoods . Its epicenter was in Orange County , one mile east of La Habra and four miles north of Fullerton , the U.S. Geological Survey said . Shortly after the earthquake , nearly two dozen aftershocks followed . A magnitude-4.1 shake rattled the area Saturday afternoon , centered about a mile and a quarter southeast of the Los Angeles County community of Rowland Heights , the geological agency said . After the Friday night earthquake , authorities said police and local fire departments assessed affected areas and found no damage or significant injuries . One minor injury was reported in Orange County , emergency officials said . `` Tonight 's earthquake is the second in two weeks , and reminds us to be prepared , '' Los Angeles Mayor Eric Garcetti said . An hour earlier , a magnitude-3.6 tremor struck the same area , according to the U.S. Geological Survey . The quakes come on the heels of a magnitude-4.4 tremor that hit near downtown Los Angeles a week ago . It shook nearby buildings but did not cause significant damage . Southern California has experienced relatively minor tremors since 1994 when a magnitude-6.7 quake killed dozens and caused $ 42 billion in damage . It now stands as the second-costliest disaster in U.S. history , after Hurricane Katrina . Earthquakes with less than magnitude 5.5 do n't usually cause significant damage or casualties , though results vary by region , geophysicist Paul Caruso said . Damage often depends on construction codes and types of rock that exist underground , he said . Measuring the magnitude of earthquakes . The place where two earthquakes hit every hour .
A large earthquake rattles the Los Angeles area this afternoon , USGS says . No fatalities or significant injuries found in affected areas , they say . A series of aftershocks occurred after the quake . ` ` Earthquake is the second in two weeks , '' Los Angeles mayor says .