Research Professor of Geophysics

Seismic Networks

The authoritative earthquake-monitoring region of the Southern California Seismic Network (SCSN) extends across southern California, from the US-Mexico international border to Coalinga and Owens Valley in central California. The SCSN also reports on earthquakes in northern Baja California, Mexico because these could possibly cause damage in the United States. The region is home to 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. Emergency managers use SCSN information to coordinate rescue operations, guide inspectors in the search for damage, and to facilitate disaster recovery. The media broadcasts the earthquake information to satisfy public need for information.

The SCSN processes and records real-time data from about 425 seismic stations. It operates about 300 seismic stations and receives real-time waveform data from an additional 125 stations operated by partner networks. The SCSN seismic stations can be divided into three groups. First, the most modern group of 170 SCSN stations consist of broadband sensors, strong motion sensors, and high resolution dataloggers for digitization and data communications. The data from these stations are used for real-time determination of earthquake locations, magnitudes, moment tensors, and amplitudes for ShakeMap. The second group consists of about 35 stations that are equipped with only strong motion sensors and a datalogger. These stations provide amplitudes for ShakeMap and occasional arrival-time picks. The third group consists of 125 short-period stations that use legacy analog, frequency-modulated (FM) audible tone technology and Earthworm digitizers for data acquisition. These stations are low-cost and can be installed at seismically quiet sites with minimal security. The waveform data can be transmitted for long distances using analog FM radio with very low bandwidth. Although, the amplitude data have limited dynamic range and are often only calibrated using nominal response values, these stations provide arrival-time picks for improved location and depth determination as well as coda duration for determining magnitudes of small earthquakes. Eight Earthworm hubs that are spread across southern California aggregate the SCSN short-period stations and transmit digital waveform data to the central site in Pasadena.

Additional information available from: