Delineation of 3D crustal seismic structures beneath western Tibet and the Himalayan range using local earthquake tomography

This study aims to image the crustal structure of the western Tibetan Plateau by analyzing the velocity structure of elastic waves, using manually picked P- and S-wave arrival times from waveform data recorded by temporarily installed seismic stations in western Tibet. Preliminary events located using the VELEST algorithm resulted in the development of a 1-D velocity model through inversion, which was then used in the TomoDD algorithm to relocate earthquakes and generate a high-resolution 3-D velocity structure model. A significant number of events were located between the Karakoram fault (KKF), Main Boundary Thrust, and Main Central Thrust. A low P-wave anomaly of approximately ~8% is noted in the vicinity of the KKF, while a significant low P-wave anomaly is also observed in the crust beneath the western margin. A low P-wave anomaly is concentrated beneath the Lhasa block, whereas a relatively higher P-wave anomaly is evident in the Himalayan terrane. The KKF dips beneath the Tibetan plateau towards the northeast. Evidence of partial melting in the crust beneath the Tibetan plateau and mid-crustal channel flow of slower crustal material from the plateau towards the Himalayan range can also be delineated through the observed velocity structures found in the study.