We use teleseismic data from the Jammu and Kashmir Seismological NETwork, to perform P-wave receiver function spatial and common-conversion-point (CCP) stacks, and joint inversion with Rayleigh-wave group-velocity dispersion, to construct 3D Vs model of the Jammu and Kashmir (J&K) Himalaya. 2D-CCP and Vs profiles reveal increasing crustal thickness from the foreland-to-hinterland, and an under-thrust Indian crust beneath J&K. The Moho positive impedance-contrast boundary is at ∼45 km depth beneath Sub-Himalaya and deepens to ∼70 km beneath Higher-to-Tethyan Himalaya, with an overall gentle NE dip. The Main Himalayan Thurst (MHT) forms a low velocity layer (LVL) with negative impedance contrast, and has a flat–ramp geometry. The flat segment is beneath Sub-to-Lesser Himalaya at 6–10 km depth, and dips ∼4◦. The mid-crustal (frontal) ramp is beneath Kishtwar Higher-Himalaya and Zanskar Ranges at 10–16 km depth, and dips ∼13–17◦. Significant along-arc variation in crustal structure is observed between east (Kishtwar) and west (Kashmir Valley) segments. Beneath the Kishtwar Window we image a Lesser Himalayan duplex (LHD) bound between MHT sole-thrust and MCT roof-thrust. LHD horses dip at high angle to the bounding structures and are illuminated by moderate seismicity. Beneath the Pir-Panjal Ranges and Kashmir Valley, the underthrust crust is ∼10 km thicker, has higher crustal Vs , and a shallower flat MHT at ∼10 km depth. The westward shallowing of the MHT occurs through a lateral ramp beneath Kishtwar Himalaya. Aftershocks of the 2013 Kishtwar earthquake concentrate on the MHT frontal and lateral ramp intersection, and possibly marks the down-dip locked-to-creep transition.

Nepal is an actively deforming region due to its tectonic setting that hosts many destructive earthquakes including the recent 2015 Mw 7.8 Gorkha earthquake. To better understand the physics of earthquakes and their precise location as well as monitoring of seismicity and real-time seismic hazard in the region, a highly resolved 3-D structure of the crust is essential. This study presents a new 3-D S-wave velocity structure of the crust using ambient noise tomography (ANT). This study further constrains the discontinuities beneath Himalaya Nepal using teleseismic P-wave coda autocorrelation. The results from the P-wave coda autocorrelation identify major seismic discontinuities in the crust including the Main Himalayan Thrust (MHT). The MHT with two ramps correlates well with a low S-wave velocity layer obtained from the ANT. The first ramp agrees with the duplex structure in the MHT beneath Lesser Himalaya while the second connects flat low velocity beneath High Himalaya to a broad low-velocity zone beneath South Tibet. The geometry and extent of the High Himalaya low-velocity layer mimics the decollement coupling zone inferred from GPS data with widths of 50-70 km north of the nucleation of the 2015 Mw 7.8 Gorkha earthquake and 90-100 km north of the source of the Mw 8.4 1934 earthquake. The occurrence of millenary Mw>9.0 earthquakes in Central and Eastern Nepal would require either a wider coupling low velocity zone compared to the ones identified in this work or the involvement of southernmost Tibet low velocity decoupling zone so to store enough elastic energy.