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Extracted text: Q.13.22 A seismic survey was carried out for a large project to determine the nature of the substrata. The results of the survey are given in Fig. i :in the form of a graph. Determine the depths of the strata. V, = 2250 m/sec D. xS x 10 Surface soil V = 750 m/sec Sand and loose gravel V, Rock AB, = 8.75 x 10' see AC, = 33.75 x 10' sec AC: = 38.75 x 10' sec d, = 2.188 m d = 22.5 m AB = 12,75 x 10 sece V = 172 m/sec 10 20 dz 30 40 50 Distance m Figure Time of first wave arrival, seconds