THE EFFECT OF THE NUMBER AND SPACING OF ELEMENTS ON THE EFFICIENCY OF LASA BEAMS
Abstract
LASA short-period recordings of 8 teleseismic earthquakes were prefiltered and beamsteered on P-wave arrivals across the 200 km. aperture to establish the relationship between sensor spacing and beam efficiency in terms of noise reduction, signal loss, and S/N ratio improvement. Results show that the combined effect of increasing the number of elements in a beam while simultaneously reducing inter-sensor spacing is to produce progressively less rms noise reduction and S/N gain relative to N to the 1/2 power. The study further shows that beamforming each of the events in two ways, e.g., with 51 and 525 inputs, produces an average signal loss of approximately 4 db. Moreover, beaming the samller number of traces reduces rms noise and improves S/N only about 1 db less than the 525-element beam. For the 51-element beam, the minimum sensor spacing was 6 km., the distance at which the short-period noise at LASA becomes incoherent.
Document Details
- Document Type
- Technical Report
- Publication Date
- Dec 21, 1967
- Accession Number
- AD0824795
Entities
People
- R. A. Hartenberger
Organizations
- Teledyne Technologies