A study of the Earth's crust near Gauribidanur in Southern India

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Abstract
A hypothetical two-layered model has been evolved for the Earth's crust near Gauribidanur. The model is found to be consistent with the local earthquake and rockburst data obtained at Gauribidanur seismographic array. Sixty-seven well-recorded seismic events have been studied for this purpose. First arrival conditions for some of the phases in a “near-source” (epicentral distance Δ ≦ 10°) seismogram have been derived and subsequently made use of in establishing the nature of the first arriving phases pertaining to the available data. Thickness of the top granitic layer and the depth of Moho below this layer are found to be about 16 km and 19 km, respectively. Observed velocities are 5.67, 6.51 and 7.98 km/sec for P phases, and 3.46, 3.96 and 4.61 km/sec for the corresponding S phases. Values of the crustal parameters given by this study have been used in estimating the relative differences in travel times corresponding to various observed phases. These travel times may improve the precision with which earthquakes in this region could be located. Typical geographical and geological features of the region are also briefly described.