Integrated Array and 3-Component Processing Using a Seismic Microarray
Abstract
A microarray as defined in this paper is modeled on a subgeometry of the NORESS array (Mykkeltveit al., 1990), 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 (a) multiple-band filtering, (b) coherent and incoherent beamforming, (c) STA/LTA threshold detection, (d) broadband frequency-wavenumber (f-k) analysis and (e) 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 per cent 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.
Document Details
- Document Type
- Technical Report
- Publication Date
- May 31, 1991
- Accession Number
- ADA240139
Entities
People
- F. Ringdal
- T. Kvaerna
Organizations
- Royal Norwegian Council for Scientific and Industrial Research