Estimation of travel time of P- and S-waves in and around Sylhet and Mat faults in Surma Basin, northeast India


A regional seismicity map for Surma valley and the adjoining region, covering the area bounded by longitudes 90-95°E and latitude 22-26°N was prepared covering the period between 1969-2009 over the generalized tectonic map of the region. The best estimation ofhypocentral parameters form the prime input for the estimation of travel time of P- and S- waves of any region. The Riznichenko diagrams clearly show the change in shape of the travel time versus distance with increasing focal depth, indicative of both a geometrical effect and an increasing P-wave velocity. The Wadati diagrams show systematic decrease in ts/tp, suggesting that the velocity for shear waves increases faster than that for the compressional waves in the upper levels of the crust.

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