The speed of Pans S waves are 8.5Km/s and 5.5Km/s respectively. How far did the epicentre if the waves are detected 17 min apart?
time difference = 17 * 60 = 1020 seconds
distance P = 8.5 Tp
distance S = 5.5 Ts
same distances so 8.5 Tp = 5.5Ts
but Ts = Tp + 1020
so
8.5 Tp = 5.5 (Tp+1020)
3 Tp = 5610
Tp = 1870 seconds
1870 seconds * 8.5 km /s = 15,895 km
(opposite side of earth? check my arithmetic)