Inversion of seismic intensity data for the determination of three-dimensional attenuation structures in the central gap region of Himalayas

The central gap region of Himalaya, which lies in the northern part of the Indian subcontinent, is exposed to great seismic hazard. A three-dimensional attenuation structure (Q) of this region is obtained using the intensity data of four earthquakes (M 4.3–7.0) in the central Himalayan gap region and the damped least square inversion scheme. The technique is based on that given by Hashida and Shimazaki (J Phys Earth 32:299–316, 1984). The obtained Q structure explains the spatial distribution of isoseismals of the stronger earthquakes, which occurred in the recent past. The study area covers the Tehri town, which is the locale of one of the biggest earth fill dams of height 260 m. The spatial distribution of Q suggests that the Tehri town area is surrounded by lower Q medium, and hence any large earthquake in Tehri will pose great seismic hazard.