Fault length and fracture velocity for the Kyushu, Japan, earthquake of October 3, 1963

The long-period P waves from the Kyushu, Japan, earthquake of October 3, 1963 (h = 33 km, M = 6½) are analyzed for a propagating source effect on their temporal behavior. The time duration of the first half-period is shown to be azimuthally patterned but distance independent. Preservation of the wave form character at the World-Wide Standard Seismographic Network (WWSSN) stations is shown. Distortion of the pulse emitted by the source is shown to be more probable for the PcP phase than for the pP phase. Matching the observed wave forms with theoretical P wave seismograms leads to an estimate of the fault length as 25 km, the faulting pattern as bilateral, and the average fracture velocity as 3 km/sec. The observed data (first half-period of the P waves) are matched to propagating-source theory with a standard deviation of 0.6 sec.