LASA ON-LINE DETECTION, LOCATION AND SIGNAL-TO-NOISE ENHANCEMENT
MASSACHUSETTS INST OF TECH LEXINGTON LINCOLN LAB
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This report describes the results of carrying out a number of seismic signal handling operations in on-line digital equipment at the Large Aperture Seismic Array Data Center in Montana. An appraisal is made of the threshold detection capability of a single LASA sensor by comparison with two well- calibrated stations nearby, UBSO and UMSO. It was found that signals average slightly higher at LASA than at these other stations. When the detection threshold of one LASA sensor is corrected for the predetection processing gain being achieved by current LASA beamformer programs, a LASA detection threshold for event detection by surveillance is established. This number is at a C. and G. S. magnitude of 3.7 for 75 detection or 3.5 for 50 detection by a single LASA for events 30 to 90 degrees away. Some further improvement is possible by more careful on-line beam processing. A combination of automatic event detection and location programs working from individual subarrays is described. This program has been used on single seismometer outputs, giving a 75 threshold for detection and location at a C. and G. S. magnitude around 4.2. Methods for lowering this by various predetection processing schemes are compared.
- Seismic Detection and Detectors