S/P Travel Time Ratio in Central Asia
Annual rept. 1 Oct 1973-30 Jun 1974
TELEDYNE GEOTECH GARLAND TX
Pagination or Media Count:
The SP travel time ratio for intermediate depth Hindu-Kush earthquakes and shallow earthquakes in the Hindu-Kush, Pamir, and Tien Shan regions is investigated, using S and P arrival times at 6 World Wide Standard Seismograph Network stations and 19 other close-in stations. For intermediate depth earthquakes, station mean values of the ratio average 1.78, ranging from 1.76 to 1.81. The ratio increases slowly with increasing distance over the range 4.5 to 13 degrees and increases rapidly with decreasing distance for distances less than 4.5 degrees. Variation of the ratio with focal depth is weak. For shallow earthquakes, station mean values of the SP travel time ratio average 1. 78, ranging from 1.75 to 1.83. For the distance range 6.5 to 14 degrees, variation of the ratio with distance is weak, and for distances less than 6.5 degrees the ratio increases with decreasing distance. The SP travel time ratio increases with increasing focal depth, the depth dependence being stronger at closer distances.