Geothermal and seismic evidence for the fluids in the crust beneath Koyna,India

The presence of fluids in the crust beneath Koyna region has been examined, by computing the isochoric thermal pressure, pore fluid pressure and pore fluid factor at the pressure-temperature beneath the area. A reduction of 0 .2 km/s in compressional wave velocity in the depth range from 6 to 11.5 km beneath Koyna region as revealed by DSS studies is not an unequivocal cons traint about the existence of fluids in the shallow crystalline crust. Ther efore, these data along with the geothermal seismicity of the region and ot her relevant data have been considered and isochoric thermal pressure (19 t o 21 bar/degrees C) and pore fluid factor (0.78 to 0.83) were analysed to e valuate the possible presence of fluids. These results indicate the existen ce of sialic low velocity layer enriched in fluids beneath Koyna area.