we ve had small vegetation fires. power lines down. gas leaks. reporter: 20 victims taken to ridgecrest hospital, where at the same time, they had to evacuate part of it due to unsafe conditions. the computers were flying off onto the ground. the water bottle container was shaking, all the cupboards and doors were opening. reporter: roads ripped open outside of town. this liquor store destroyed. contents of these supermarket shelves tossed to the floor. a big jolt and felt all over southern california. reporter: the quake lasting at least 20 seconds, felt as far away as las vegas. in los angeles, water mains bursting. all units, all units, we are on city-wide earthquake mode. reporter: crowds of people pouring out of buildings onto the streets. seismologist lucy jones says this was a strike-slip quake. that means the two plates along the fault move parallel to each other, but in opposite directions. she says 30 minutes before the main quake, there was a 4.2