| Abstract Submission No. | ABS-3.1-0226 |
| Title of Abstract | Crust and Upper Mantle Love wave Group Velocity maps of NE India |
| Authors | Nongmaithem Menaka Chanu *, Naresh Kumar , Sagarika Mukhopadhyay , Rabin Das |
| Organisation | North-East Geophysical Research Laboratory (NEGRL), Indian Institute of Geomagnetism, Shillong 793005 |
| Address | North east Geophysical Research Laboratory, IIGM, 3.5 Upper Shillong SHILLONG, Meghalaya, India Pincode: 793005 E-mail: menaka.nongmaithem@yahoo.in |
| Country | India |
| Presentation | Poster |
| Abstract | In the present study, fundamental mode Love waves with periods ranging from 6 to 60 s are used to obtain group velocity maps in Northeast India. A total of 880 ray paths are obtained using 228 local and regional earthquakes (5 Mw 7.9) recorded by 26 seismic stations. Contrasts in group velocity tomography images at different periods mirror significantly different crustal structures. In periods < 16 s, BB, IBR, EHS, the upper part of BRV, Assam syntaxis, and part of Tibet display low velocities, significantly lower than those of the Shillong Plateau, Mikir Hills, and the Eastern Himalayan Ranges (EHR). Low-velocity zones in BB and IBR systematically shift eastward toward the southern part of the IBR for 16 to 42s, and with increasing period, group velocity increases. Observed low-velocities in the upper part of BRV and within the BB, IBR, and Assam syntaxis indicate the presence of sedimentary layers in the uppermost crust. However, low velocities observed in the higher periods in the BB and IBR indicate thicker sedimentary deposits in these regions. The western part of the BB exhibits higher group velocities compared to the BB in the east, indicating an increasing basement depth from west to east. With increasing periods up to 60s, the area of highest velocity is observed in the SP, Rajmahal trap, and Singhbhum craton due to a thin crust or shield materials. Thickness of the crust increases toward the Indo-Burmese subduction in the east and the India-Asia collision in the north. At periods >50s, lower velocity is observed in the Tibetan plateau, indicating the presence of a thicker crust. The low velocity from ~27 s to 50 s in the Tibetan Plateau is an indication of partial melts in the middle-to-lower crust, which is also reported in several studies. |
| Keywords | Love wave, Dispersion curve, Tomography images, Crustal structure. |