Radiation pattern of Rayleigh waves from the southeast Alaska earthquake of July 10, 1958

Abstract

Long-period Rayleigh wave data obtained during the IGY are used in this paper to measure the initial phases and amplitudes of Rayleigh waves as a function of azimuth for the Southeast Alaska earthquake of July 10, 1958. This study indicates that the radiation pattern bears a simple relation to the fault motion, showing four sectors of initial phase and a four-lobed pattern of amplitudes. The symmetry of the radiation pattern is in agreement with the motion on the fault as determined by a fault.-plane solution and by field observation of the direction of faulting. The symmetry differs radically from that expected from explosions. It is concluded that this simple technique can be used to study focal mechanism from surface wave data for most of the larger earthquakes when instrumentation is improved and regional variations in phase velocity for shorter periods are known.