DETERMINATION OF LASA DETECTION AND LOCATION ABILITY USING KURILE ISLANDS EVENTS
MASSACHUSETTS INST OF TECH LEXINGTON LINCOLN LAB
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The Kurile Islands Ocean Bottom Seismographic Experiment of late 1966 provided a source of epicenters for small regional and local events in a seismic region. Epicenters obtained from ocean bottom seismometer data and from the U. S. Coast and Geodetic Survey were used to evaluate the Montana LASA epicenter location ability. Epicenters determined by a plane wave approximation method gave mislocation errors, relative to the CGS locations, that averaged about 60 km. The same events were mislocated an average of 80 km when the epicenters were determined by a closely spaced grid of beams. Although the beam epicenter locations were worse than those of the plane wave method, the beam location method was able to produce epicenters for magnitudes well below the threshold of the plane wave method. The events in this experiment represent a sufficiently large population on which beam detection thresholds can be evaluated. The detection thresholds that were obtained confirm earliest predictions based on extrapolation from a single sensor. The detection results indicate that a 90- percent cumulative detection on a LASA beam will occur at about magnitudes 3.85 and 4.15 for a seismicity curve with a slope of 0.75 and 1.0, respectively.
- Physical and Dynamic Oceanography