Large thrust faults accommodate the convergence between India and Tibet along the
southern margin of the Himalaya and have a history of producing great earthquakes
that cause widespread damage. Along most parts of the Himalaya, there is geomorphological
evidence that these thrusts can rupture to the surface in M-w >8 earthquakes. However,
in the Himalayan state of Jammu & Kashmir (NW India), the thrust faults are blind
and large-scale folding is the only expression of active deformation at the surface,
making it difficult to assess the seismic hazard in this region. In this paper, we
use field, satellite, and seismological observations to determine the fault geometry
in Jammu & Kashmir. We then estimate the ground motions from potential earthquakes
in the region using models of the seismic wavefield that would be generated if the
thrust fault beneath Jammu & Kashmir were to rupture. We find that earthquakes that
rupture the buried, shallow part of the locked Main Himalayan Thrust could generate
peak ground velocities that are >3 times larger than earthquakes of the same magnitude
on its deeper portions. We also model the ground motions that would result from the
thrust fault geometries representative of different parts of the Himalayan arc. These
simulations show that even seemingly minor variations in the shallow fault geometry
can lead to large differences in the expected ground motions, highlighting the importance
of accurately determining the shallow geometry of thrust faults along the margins
of mountain ranges for estimating seismic hazard.
