Earthquakes and Earthquake Damage in Southern California

Although problems of the seismic activity of any region or of the world are best handled in terms of the earthquake magnitude scale, this scale will not serve the needs of the engineer and field geologist who wish either to relate effects on structures, ground, and ground water to the intensity of local shaking, or to interpret intensity in terms of surface and subsurface structure and the generating mechanism of earthquakes. The magnitude scale attaches a single number to the earthquake as a whole (see Richter and Gutenberg, Contribution 3, Chapter IV); for detailed statement of the variation of effects from point to point an intensity scale is needed