Ground Motion in Delhi from Future Large/Great Earthquakes in the Central Seismic Gap of the Himalayan Arc

Abstract We estimate ground motions in Delhi from possible future large/great earthquakes in the central seismic gap in the Himalayan arc. The closest distance from the rupture areas of such postulated earthquakes to Delhi may be about 200 km. We have used two methods to synthesize the expected ground motions. In the first, recordings in Delhi (three on soft sites and one on a hard site) of the 1999 Chamoli earthquake (Mw 6.5; epicentral distance, 300 km), which was located in the gap, are used as empirical Green’s functions (EGFs). The ground motion during the target event is synthesized by random summation of the EGFs. In the second, the stochastic method, the motions have been estimated from the expected Fourier spec-trum of the ground motion in Delhi through the application of Parseval’s theorem and results from random vibration theory. We apply two versions of the stochastic method: the first assumes a point source while the second considers the source to be finite. The predictions from the two methods are in reasonable agreement for Mw 7.5. For Mw 7.5 events, the finiteness of the source becomes important. Several rupture scenarios are considered in the application of the finite-source stochastic