Basement Configuration of the Area West of Koyna (India) from the Analysis of Aeromagnetic Data

An aeromagnetic map of the area west of Koyna (lr23' N, 73°45' E), bounded between latitude 17°5' Nand 17°35' N and longitude 73°15' E and 73°40' E, is spectrally analysed to derive a basement relief model. The model reflects structural heterogeneity conforming well with the existing estimates of trap thickness from other geophysical methods. Two prominent structural features-one near Chatnali and the other to the west of Durga Dongar-are observed which indicate fault-like structures. Between south of Alore and northeast of Mutagaon, a body with high reverse magnetization with its top lying at a depth of about 1200 m is also indicated. These results seem to indicate a limited triggering role of reservoir-induced seismicity in the region and point to the existence of pre-reservoir instability of the Koyna zone.