A semiautomatic calibration method applied to a small-aperture Alaskan seismic array

摘要

Small-to-medium aperture (25 km or less) seismic arrays are of great importance for event location and characterization. Effective use of these arrays requires calibration, preferably with large numbers of events, to account for local and distant structural and propagation effects. We implement a cross-correlation method as a semiautomatic procedure applicable to any small array, able to process thousands of events with several days of computer time on a Sun Blade 1000 workstation. We analyze a database of 1228 P and PcP arrivals recorded between 1997 and 1998 at a 19-element Alaskan seismic array. The arrivals are picked by the Prototype International Data Centre for events well located by the United States Geological Survey. Backazimuth and horizontal-velocity residuals are calculated for all events. Complicated geology beneath the elements and elevation differences among the array stations make static corrections necessary. We use 328 core phases (including PcP, PKiKP, PKP, PKKP) to determine the static corrections. We present first-order structural interpretations of our calibration results, including a Moho discontinuity dipping to the north with a 10.5 degrees dip angle and a strike of 109 degrees. Our method allows for resolution of phase arrivals within 2-3 see and has potential to be used as an automatic detector of primary and secondary seismic phases.