Accession Number : ADA328331

Title :   Earthquake Focal Mechanisms in Northeastern China and Korea Determined by the Grid Search Algorithm.

Descriptive Note : Scientific rept.,

Corporate Author : PHILLIPS LAB HANSCOM AFB MA

Personal Author(s) : Cipar, John J.

PDF Url : ADA328331

Report Date : 29 AUG 1996

Pagination or Media Count : 31

Abstract : The grid search algorithm for determining earthquake focal mechanism and depth is tested by inverting regional-distance seismograms for a suite of five earthquakes in northeastern China and Korea. An improved crustal model for the region is used to compute the synthetic Green's functions for the eight fundamental fault types. To account for uncertainty in timing, location, and crustal structure, the synthetics are time shifted during the inversion to produce the best match. This process is repeated at a range of source depths. The focal mechanisms and depths for the earthquakes studied in this report are broadly consistent with teleseismic measurement of earlier large events in the region. The average time delays at each station and for each event provide a measure of the uncertainty in origin time and velocity structure. Either crustal velocity variations of 1-2 percent, or incorrect event locations of about 10 km, could explain the observed delays.

Descriptors :   *EARTHQUAKES, *EARTH MODELS, *STRUCTURAL GEOLOGY, VELOCITY, ALGORITHMS, TIME INTERVALS, MEASUREMENT, UNCERTAINTY, GRIDS, VARIATIONS, EARTH CRUST, SEISMIC WAVES, KOREA, CHINA.

Subject Categories : Seismology

Distribution Statement : APPROVED FOR PUBLIC RELEASE