The Kinnaur earthquake, Himachal Pradesh, India, of 19 January, 1975

Abstract

Determination of the fault-plane solution of the Kinnaur earthquake by first motion and amplitude data of P waves, along with other geological and geophysical data, indicates a N-S-trending and westward-dipping fault plane with purely dip-slip displacement. This plane coincides with the N-S extending zone of aftershocks, ground fissures and faults observed in the epicentral tract following the earthquake. The cumulative strain release pattern displays a characteristic release of logarithmic recovery followed by exponential recovery. The aftershocks display a notable migration in space. They also show two distinct phases of seismic activity. The main earthquake is estimated to have a fault length of 25 km, fault area of 575 km², volume of strain of ~2900 km³, displacement of 59 cm, stress drop of 36 bars, and strain release of 5.9 . 10^-5.