The Norwegian Seismic Array (NORSAR)
Abstract
The Norwegian Seismic Array (NORSAR) Detection Processing System operated during the period 1 April - 30 September 1984 with an average up time of 95.1%. A total of 2160 seismic events were reported in this period. A seismic waveform injection technique has been developed and applied to deep events in the Fiji Islands region. Preliminary results show no compelling evidence for significant deviations from the double couple mechanism; and the data are consistent with a stress drop in the range 10-100 bars. A new method for dynamic ray tracing is being developed, and has been tested against simple analytical models. An investigation of optimum data processing schemes for regional arrays has shown the need for operating over a relatively wide band of frequencies (2-8 Hz) in order to ensure adequate SNR for various signal paths (oceanic, mobile cratonic belt, shield). SNR gains of 2-4 dB (up to about 5 Hz) relative to conventional beamforming can be obtained using optimum weighting, whereas a simplified scheme of 0/1 weighting gives 1-2 dB less gain. An investigation of high-frequency P-wave attenuation from Central Asia to Norway has shown that for recordings of Semipalatinsk explosions there are almost no frequency-dependent effects in the attenuation between 3 and 7 HZ, thus confirming the assumption that the source spectrum of such events is proportional to 1/f (sq) above the corner frequency.
Document Details
- Document Type
- Technical Report
- Publication Date
- Nov 01, 1984
- Accession Number
- ADA154751
Entities
People
- L. B. Loughran
Organizations
- Royal Norwegian Council for Scientific and Industrial Research