FREQUENCY-WAVENUMBER ANALYSIS OF SIGNALS AND NOISE RECORDED AT THE VERTICAL ARRAY AT APACHE
Abstract
The seismic data analyzed include an Aleutian earthquake, several samples of ambient noise along with the noise occurring before the event, and a 25 second sample of coda following the signal. The signal coda sampled had nearly uniform power. A preliminary interpretation of the noise and signals strongly suggests the importance of energy conversions possibly due to the complex geology at APOK. The geology is known to be very complex and is characterized to first order a thick wedge of low velocity strata imbedded in material of higher propagation velocity. The evidence of conversion is based on the asymmetry of the F-K spectrum of ambient noise with respect to positive and negative wave number. The results indicate a predominance of obliquely incident up-going waves at all frequencies. Further, the signals and coda similarly displayed anomalous down-going pulses attenuated by approximately 6 db with respect to the up-going pulse. Further, the down-going pulse contains lower frequencies than the up-going pulse and has a much lower apparent vertical velocity. The results obtained by mirror imaging the vertical array indicated that a loss of approximately 3 db would be encountered in using a conventional signal model at this site.
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 08, 1967
- Accession Number
- AD0819939
Entities
People
- Robert L. Sax
Organizations
- Teledyne Technologies