Emergency crews in Southern California are responding to at least 24 medical and fire incidents in the wake of a 6.4 magnitude earthquake that struck near Ridgecrest, California, home to about 28,000 people. There have been no reports of injuries in the Los Angeles area, which is located about 240-kilometres southwest of the epicentre. But it could be felt from Las Vegas to the Pacific Coast. One veteran seismologist says this is the strongest quake to hit Southern California in 20 years. In the middle of the 4th of July Parade in Huntington Beach, local news anchors interrupted their commentary to let viewers know there was an earthquake. For images posted to YouTube from California residents, click here