- © 2006 by the Seismological Society of America
The authoritative region of the Southern California Seismic Network (SCSN) extends across southern California, from the U.S./Mexico international border to Coalinga and Owens Valley in central California (Figure 1). This area contains almost 20 million inhabitants, including two of the ten largest cities in the United States (Los Angeles and San Diego) and the two largest harbors (Los Angeles and Long Beach) in the nation. SCSN also reports on earthquakes in Baja California, which could potentially cause damage in the U.S. More than fifty earthquakes (not including aftershocks) are felt each year, and an average of 1.5 events per year are potentially damaging (magnitude greater than 5.0). Immediately after a moderate or large earthquake, SCSN provides information about the size, location, and distribution of ground shaking. Emergency managers use this information to coordinate rescue operations, guide inspectors in the search for damage, and satisfy the public's need for information. The historical record of earthquake occurrences in California is important to insurers, geotechnical engineers, and city planners.
SCSN has maintained and published a catalog of earthquakes complete above about magnitude 3.0 since 1932, and above about magnitude 1.8 since the late 1970's, with relatively consistent magnitudes (mostly ML) over the whole time period. Digital seismograms are available since the late 1970's, and selected seismograms since 1962 have been scanned.
Much has changed in SCSN since the last Network Bulletin (Wald et al., 1998) was published, which described changes that took place during 1997. More than half the new stations have modern broadband sensors and strong-motion sensors, and dataloggers with continuous telemetry. Many of the remaining analog stations are digitized on Earthworm hubs (Johnson et al., 1995) at field sites and telemetered to the data-processing facility in Pasadena, California. Online and offline data processing has been converted completely from …