by K.Silpa and Anil Earnest

Kinematic source process models using tele-seismic waveform inversion of three stable continental region (SCR) earthquakes from India (1993 Mw 6.2 Latur, 1997 Mw 5.8 Jabalpur and 2001 Mw 7.6 Bhuj) are presented in this paper to demonstrate the slip evolution and stress drop. These finite-fault models are methodologically unique to constrain the source dimensions, compared with assumptions and quasi-observations around blind faults. Our results show that these events do have a compact zone of singular asperity breakage within the Indian crust. Whereas the Bhuj and Jabalpur events have their rupture majorly restricted within the lower crustal regions. The Latur event ruptured a very shallow crustal asperity. The estimated rupture velocities are in the range of 2.6–3.2 km/s, Bhuj event the slowest and lengthiest. Our results do not favour an updip shallow component of asperity breakage for the Bhuj earthquake, as evident from lack of surface ruptures. Study also indicates that the 1993 Latur event occurred on a fault with high stress concentration which indicates stronger fault asperities or slip within a newer fault. Models on 1997 Jabalpur event imply higher frictional strength and very brittle nature at the lower crustal regions of the Indian slab, indicating a mechanically very strong lower crust. We conclude that an event like Latur can occur anywhere within continental interiors of Indian SCR, or elsewhere globally, and is an underestimated seismic hazard.

Source:https://doi.org/10.1016/j.quaint.2020.12.035