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Abstract:
We present the surface wave dispersion results from the recorded data of 16 broadband seismic stations in the Higher Himalaya region. The Higher Himalayas is seismically very active due to the convergence of the Indian Plate and the Eurasian Plate along a basal decollement known as the Main Himalayan Thrust (MHT). A portion of the area is located in the Kashmir seismic gap, which lies between the Kangra earthquake of 1905 and the Kashmir earthquake of 2005. A surface wave dispersion analysis has been carried out in order to understand the seismotectonic structure beneath the research area. The fundamental mode Rayleigh wave Green's functions have been estimated for station pairs using cross-correlation of vertical component ambient noise data. The generated group velocity maps from 2 to 15s indicate the substantial variation in crustal structure and exhibit strong relationships with well-known geological and tectonic phenomena in the studied region. We found a low-velocity zone in the middle crust of the higher Himachal Himalayas portion between 12 and 15 km deep, which may be caused by the presence of a crustal ramp structure beneath 12 to 22 km of the Main Central Thrust (MCT). Likewise, a shear wave velocity model has been obtained by inverting surface wave dispersion measurements for the Kishtwar region.
