Interseismic Coupling on the Main Himalayan Thrust, Implications for Extreme Earthquakes

Abstract:

We expand on the work of Ader et al. (2012) using GPS, levelling data, InSAR and microseismicity to determine the pattern of coupling on the Main Himalayan Thrust along the entire range front. We show that the convergence velocities are perpendicular to the curvature of the arc, and decrease to the west and increase towards the east. Motion in the east is complicated due to intraplate deformation of India which we account for using a block model. We find that the fault is fully locked along its complete length, with no resolvable creeping patches in the 0-20km seismogenic depth range. We estimate the deficit of seismic moment which accumulates in the interseismic period and investigate how this moment could be released. Analysing the current seismic catalogue of this region, we find that a significant proportion of the moment building up has not been released seismically. We suggest various reasons for this and discuss possible solutions to close the slip budget. This study places constraints on the frequency-magnitude of the most exterme events which could occur in the Himalaya.