On relation between seismicity and tectonic features of Idukki region, Southwestern India

Abstract

The detailed investigations of the lineament and seismicity data of Idukki area have been carried out in connection with the location of June 7, 1988 earthquake and its associated significant aftershocks. The analysis of lineament data has indicated three major lineaments namely Idamalayar, Periyar and Kambam which have influenced the entire lineament fabric of the Idukki area. The study has indicated that the June 7, 1988 earthquake was associated with Periyar lineament in Nedumkandam area which has been found to be located at a distance of 22 km off Idukki. It has been observed that the isoseismals pertaining to maximum intensity VI MM and above show unidirectional elongation in WNW-ESE while lower intensity isoseismals have bi-directional elongation in WNW-ESE and NE-SW. The Periyar lineament trending WNW-ESE and NE-SW trending Kambam lineament have served as conduits for the propagation of seismic energy over long distances since its transmission is more efficient along rupture zones than in the transverse direction.