Earthquake origin time is found from the P-S arrival time interval using the P and S wave velocities: the S-P interval is proportional to distance, and dividing by (Vp - Vs) gives travel time, which is subtracted from the P arrival time.
S-P interval = 8:31:16 - 8:30:04 = 72 s. With Vp:Vs = 1.6:1, the P travel time from origin equals (S-P interval) x Vs/(Vp-Vs) =...
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