A PC-based broadband digital seismograph network

SUMMARY A regional telemetry network of digital seismographs, the Berkeley Digital Seismograph Network (BDSN), is being installed in Central California to upgrade the permanent University of California seismographic stations which data from 1887 at Lick Observatory and Berkeley. The design aims are low cost, use of available personal computer (PC) technology, continuous recording, unattended operation and low error rate. The scientific aims are full wave recording of both local and teleseismic events from micro-to-great earthquakes, rapid observatory analysis, data dissemination, and enhanced research. Streckeisen three-component seismometers (or equivalent) are used with PC-based 16-bit digital data acquisition and telemetry. Each remote station has satellite-clock timing, anti-aliasing filters, a plug-in analogue-to-digital (A/D) converter, a 2400 bps modem and an automatic restart timer. Three broadband channels (20 sps) and one short-period vertical channel (40 sps) are transmitted to a PC at the central station in 1 s packets for storage on Bernoulli cartridge discs (20 Mb). Each cartridge holds remote station data for one day. Error checking and packet retransmission are included in the system software. Seismograms from the 1986 October 20 Kermadec earthquake (Ms= 8.3), the 19° February 14 Coalinga, California earthquake (ML= 5.2) and the 1987 February 28 Mt Lews. California earthquake (ML= 3.6) are shown to demonstrate the system capabilities.