Here are some terms commonly associated with earthquakes:
Epicenter--The surface point directly above the point in the earth's crust where a rupture begins. The epicenter is determined by a network of seismic stations linked by telephone hookups to monitoring centers, such as those at Cal Tech in Pasadena and USC in Los Angeles.
Intensity--A subjective measure based on the effects of the quake on the surface of the earth and man-made structures. The intensity of a quake will vary with the type of soil. Generally, the harder the soil in an area the milder the intensity of a quake.
Magnitude--The maximum motions of a quake recorded by a seismograph, the Richter scale being the most common measure.
Liquefaction--A process where water-saturated sediment temporarily loses strength, usually because of shaking, and behaves like a liquid. The soil in the South Bay is mostly sediment and the water table has been rising in recent years--due to lack of consumption and high rainfall--making liquefaction an increasing danger.