Kinematics of Crustal Deformation along the Central Himalaya

Abstract

Using an updated set of GPS surface velocities, the present study provides fault locking behavior and slip rate distribution of the Main Himalayan Thrust (MHT) along the central Himalaya. The two-dimensional velocity field is inverted through Bayesian inversion to estimate fault geometry and kinematic parameters of the MHT along the central Himalaya. The modeling results reveal that: (1) MHT is fully locked in the upper flat (0-9 km), partially locked along the mid-crustal ramp (15-21 km), and it is creeping in the deeper flat (> 21 km); (2) there is an insignificant slip rate of MHT along the locked-to-creeping transition zone, indicating its partially coupled/locked behavior; (3) along the deeper flat of the MHT, the estimated creeping rate is ~16.3 mm/yr, ~14.7 mm/yr, and ~14.3 mm/yr along western, central, and eastern Nepal, respectively; and (4) along the MHT on the upper crust, the modeled locking width turns out to be 97 km, 106 km, and 129 km in the western, central, and eastern Nepal, respectively. In addition, the posterior probability distribution of the locking width exhibits a bimodal Gaussian distribution coinciding with the two ramp geometry of the MHT along the western Nepal. Along the foothills of the Higher Himalaya, the inferred locking line is also aligned to the estimated maximum shear strain concentration and observed seismicity along the central Himalaya. With a general agreement to the previous geodetic results, geological estimates, and background seismicity, our findings provide a promising avenue of the contemporary crustal deformation along the Nepal Himalaya. The estimated inversion results in a Bayesian framework exhibit updated fault kinematics of the MHT and hence provides valuable inputs for seismic hazard assessment along the central Himalaya.