Accession Number : AD0776089

Title :   Long Period Results from the International Seismic Month.

Descriptive Note : Technical note,

Corporate Author : MASSACHUSETTS INST OF TECH LEXINGTON LINCOLN LAB

Personal Author(s) : Filson ,J. R.

Report Date : 04 MAR 1974

Pagination or Media Count : 51

Abstract : Using a list of nearly 1,000 epicenters and a list of some 15,000 concurrent long period detections, an attempt is made to assign reliable surface wave magnitudes (M(s)) to the events through automatic association and magnitude determination routines. An association scheme using an average group velocity curve and a rather wide group velocity association window is ultimately used, though more elaborate schemes, such as one employing path dependent group velocities, are considered. The M(s) determination method of Marshall and Basham is extended to cover wider distance and period ranges in order to make use of very long period detections at high gain stations. Although the routines developed are not yet considered optimum, the long period network used realizes 90% cumulative thresholds of M(s) determination at body wave magnitudes of 5.3 world wide and 4.6 for shallow events in Asia. (Author)

Descriptors :   *SEISMOLOGICAL STATIONS, *SEISMIC DETECTION, *UNDERGROUND EXPLOSIONS, EARTHQUAKES, NUCLEAR EXPLOSIONS, SEISMIC WAVES, SURFACE WAVES, TABLES(DATA)

Subject Categories : Seismology
      Seismic Detection and Detectors

Distribution Statement : APPROVED FOR PUBLIC RELEASE