DATA PROCESSING

Initial data processing involved several steps, the final product of which was half-hour files containing the continuous waveform data for each station. The initial, uncompressed data set was recorded on approximately 150 Exabyte and DAT tapes, and comprised 87 Gbytes total, with the data from some stations recorded in Reftek internal format and from others in SEG-Y format. Data were converted to SEG-Y format (Table 4) at the IRIS Data Management Center (DMC) facilities in Seattle, WA, and stored on the IRIS DMC Metrum RSS-600 mass storage system.

Sorting earthquakes out of the data was accomplished in several steps. First, the trace start time in the SEG-Y headers of the continuous waveform half-hour files was changed using information from the log files recorded at each station, thereby removing clock drifts (Fig. 3). Next, processed waveforms were windowed into 150-second (local, regional, and teleseismic) and one-hour (regional and teleseismic) segments containing arrivals from each event that was recorded during the experiment. The final products of data processing are 1) half-hour files containing the continuous waveform data recorded at each station for each day of the experiment, 2) 150-second time-windowed waveform segments containing the local, regional, and teleseismic event arrivals, and 3) one-hour time-windowed waveform segments containing the regional and teleseismic event arrivals. The data can be obtained from the IRIS DMC.

Almost every station has a log file associated with it and these are included in the final data product in storage. Log files were recorded for each week (see Table 3) and the log file filename corresponds to the DAS number of the station for that week.

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