Broadband Discrimination Studies
Technical rept. 1 Oct 1978-30 Sep 1979
CALIFORNIA UNIV BERKELEY BERKELEY SEISMOLOGRAPHIC STATION
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Current studies of the manner in which elastic waves are generated by buried explosions, such as the moment tensor approach, require high-quality broadband ground motion data. In order to obtain such data at distances of a few kilometers from the source, a method or recording the ground motion with force- balance accelerometers and triggered event recorders has been developed and tested. The two NTS events EMMENTHAL and FARM were recorded in the distance range 0.5 - 10 km. A few problems with the method were identified and corrected, and it now appears to be an excellent method of acquiring data from NTS explosions at small distances. The data recorded from EMMENTHAL and FARM illustrate quite clearly a phenomenon that has been observed on records of previous events but still not very well understood. This is the matter of significant energy on the transverse component of motion, some of it arriving at the time of the P wave. This appears to be an important problem worthy of further study. Its resolution could affect the interpretation of the phases that appear on the radial and vertical components of motion.