The Southern California Seismographic Network

Abstract

Virtually everything that is known about the seismicity of the southern California region comes from the seismographic network that is centered at Caltech's Seismological Laboratory. This network was initiated in 1926 by the Carnegie Institution of Washington, operated for many years by Caltech alone, and most recently expanded as a joint effort between Caltech and the U.S. Geological Survey. More than 17,000 local earthquakes have been located and analyzed by the Seismological Laboratory during this period, and it is this body of data, in addition to the sparse pre-1926 historic record of "felt" earthquakes, together with the geologic knowledge of our active faults, that primarily determines our judgments concerning earthquake risk in various parts of the southern California region.