Abstract

An earthquake detection and recording system known as EARSS has been developed for permanent seismograph stations and temporary field installations. It records three components of ground motion with a dynamic range of 120 dB. A frequency-domain algorithm detects earthquakes and initiates the recording of data on magnetic tape. Alternatively, EARSS can record data continuously, for preselected periods of time, or recording can be triggered by a time-domain phase picker. Up to 1500 earthquakes (25.5 Mbytes) can be recorded on each magnetic tape cartridge. The field version of EARSS supplies power to the tape drive only when data is being written to tape, thus reducing the normal power consumption of 12 watts (at 12 volts) to 2.5 watts. A field trial using a network of eight EARSS seismographs resulted in 1020 successful station-days of operation from a possible total of 1098 station-days (3 years). Of the 78 lost days of operation, 23 were due to power supply problems external to EARSS, and 52 were caused by a low-temperature failure of the recording system, which has since been corrected. A total of 442 Mbytes of data were recorded, of which about 250 Mbytes were useful data.

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