Integrated array and 3-component processing using a seismic microarray
Abstract
A microarray is modeled on a subgeometry of the NORESS array, and comprises a 3-component center seismometer surrounded by 3 closely spaced vertical-component sensors deployed over a typical aperture of 0.3 km. Analysis of five days of continuous data has shown that such a system combines the benefits of array and 3-component processing in providing reliable automatic detection, phase identification, and location of weak seismic events at local and regional distances. The data processing has comprised: (1) multiple-band filtering, (2) coherent and incoherent beamforming, (3) STA/LTA threshold detection, (4) broadband frequency-wavenumber (f-k) analysis, and (5) automatic phase association and event location. Using vertical components only, broadband f-k array analysis enables correct phase identification (P-type og S-type phase) in 95 percent of the cases, and gives S-wave azimuths with a root-mean-square (RMS) deviation of 13.9 degrees from the estimates of the full NORESS array. It is particularly significant that the small array eliminates the need for introducing particle motion models, which creates ambiguities in 3-component analysis of secondary phases when interfering SH and SV phases occur.
- Publication:
-
Report
- Pub Date:
- May 1991
- Bibcode:
- 1991rncs.rept.....K
- Keywords:
-
- Arrays;
- Data Processing;
- Seismographs;
- Apertures;
- Azimuth;
- Broadband;
- Collimation;
- Detection;
- Root-Mean-Square Errors;
- S Waves;
- Geophysics