Abstract

The University of Nevada Seismological Laboratory operates an array of 60 analog short-period and 10 three-component digital telemetered seismic stations, 90 data traces in all, in Nevada and eastern California. Formerly, the seismic data streams were recorded and processed on three separate computers running disparate software and writing incompatible data formats which made access to the digital data quite cumbersome. These systems were recently replaced by a single computer system, a MicroVAX II running VAX/VMS, together with Generic CUSP (Caltech -U.S.G.S. Seismic Processing System), a controlled software system from the U.S.G.S. in Menlo Park. Telemetered digital data are stored simultaneously in two ways, unique to this network. First, these digital data are brought asynchronously into the computer using a standard direct-memory access interface and recorded continuously on an Exabyte 8-mm helical-scan tapedrive. Second, the digital data are passed through a D to A converter and intermixed with the incoming analog data stream used for routine network processing. This analog data stream is then itself digitized and presented to the computer. In this way, calibrated digital waveforms are available in the routine data processing stream, now entirely comprised of digital waveforms, used to locate earthquakes. At the same time, this allows easy access to these data in research applications involving the processing of seismic waveforms.

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