| Abstract Submission No. | ABS-3.1-0013 |
| Title of Abstract | Velocity variations across the Moho beneath the Northwest Himalaya |
| Authors | Chinmay Haldar*, Narendra Kumar, Dilip Kumar Yadav, Parveen Kumar |
| Organisation | Wadia Institute of Himalayan Geology |
| Address | Wadia Institute of Himalayan Geology Dehradun, Uttrakhand, India Pincode: 248001 E-mail: chinmay@wihg.res.in |
| Country | India |
| Presentation | Oral |
| Abstract | To accurately evaluate seismic risk and comprehend the tectonic activity in the Himalayan region, it is essential to have comprehensive knowledge of the structure of the crust and shear wave velocity contrast across Moho (δβM). Measurements of δβM are conducted using seismological data recorded at 26 BBS located in the Himalayan region. To estimate δβM, a novel technique that utilizes P-to-s converted wave amplitude data was applied. The values of δβM range from 0.7 km/s to 1.3 km/s across the area under investigation. The δβM values beneath the Himalaya region vary from 0.7 to 1.0 km/s, whereas with the presence of sedimentary layers, it jumps up to 1.3 km/s. This indicates that the presence of sediments influences the δβM values. The Moho depth has been taken from the published results below these stations. The crustal thickness (H) varies in the Himalayan region from 44 to 63 km. In the presence of sediments, H varies from 44 to 54 km below the 5 stations. The scaling relation between δβM and H is positive, which indicates the thick crust associated with a high δβM meaning that the presence of a low-velocity material may be fluid at the lower crust beneath the Himalayan region. It is proposed that the fluid, connected with the weak zone, may have activated pre-existing faults, leading to the generation of earthquakes. It is suggested that the accumulation of strain in the crust-mantle transition zone, which is rich in fluid, might be sufficient to generate seismicity in the lower crust. The identification of such a velocity contrast could allow tracking of temperature-pressure conditions responsible for the genesis of the crust-mantle boundary and their evolution. |
| Keywords | Crust, Moho, Himalaya, Receiver functions, Shear Wave velocity |