Much of our experience of earthquakes, and the major cause of damage in them are vibrations. To understand the source of this shaking, see Waves and Shaking.
Volcanoes are mountains formed by venting and cooling of lava. Volcanoes are always accompanied by earthquakes but most earthquakes occur without volcanoes. The closest volcano to southern California is Mammoth Mountain. The last explosion in the Mammoth region occurred in the 1500s and produced the Inyo craters north of Mammoth.