LARGE APERTURE SEISMIC ARRAYS
GENERAL ATRONICS CORP PHILADELPHIA PA
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Theoretical derivations and calculated array patterns are presented for the following seismic arrays the existing LASA-Montana, a random array with an aperture comparable to LASA-Montana 200 km, and continental-size array with an aperture of several thousand kilometers. The use of LASA-Montana for determining epicenters of seismic events is discussed and results are presented that indicate errors on the order of 60 kilometers. Data on the correlation across LASA of various portions of seismograms are presented, and the implications for array processing gains are briefly discussed. Two tests for identifying earthquakes with depths between 10 and 40 km are introduced, and experiments on approximately 40 seismic events, on which both tests performed quite well, are summarized. The possibility of using DIMUS processing on a seismic array is discussed. Calculations are presented based on the conventional DIMUS processing as well as on a modified DIMUS scheme that appears to be significantly better. Calculations based on several seismic events show a significant amount of signal energy in the spectral region of 4 Hz in most of the records resulting from surface-focus events. Calculations based on records from deep Fiji Island earthquakes suggest an upper mantle Q of less than 500 for that region.