Seismic waves spread outward from the fault rupture much like ripples do in a quiet pond when a stone is thrown into it. These slabs of rock are called tectonic plates. They are constantly crunching, grinding, moving into, under, over, and past each other. Tremendous pressures build up as the plate edges lock against each other. Every now and then accumulated pressures will force the edge of one massive plate past the other releasing the spent up energies of uncounted centuries.
S ometimes the plates only jump a tiny bit causing windows to rattle.
Other times the displacement is so violent that it sends seismic waves booming out in all directions with force of many atomic bombs. The result is called an earthquake. We may never see any degree of pin point accuracy. T he Southern California Seismic Network records more than 10,000 earthquakes in an average year. Not including aftershocks, about 100 earthquakes larger than 3.0 occur each year.