The Tectonic Model beneath the Northwest Himalaya Region Analyzed by Seismic Data
Speaker: Yeh Ren-jie
Abstract
The Tibetan plateau is formed by the collision of the Indian Plate and Eurasian Plate, and there the Indian Moho and the partial melt in the upper-middle crust of the Northwest Himalaya region are two focused point in this talk today. By using teleseismic data, they plotted and inverted receiver functions in order to analyze the Moho depth. Then they joined the Rayleigh wave group velocity and inverted to determine the Moho depth. According to the results, the Indian Moho deepen from the Himalaya foredeep (~ 40 km depth) to the Karakorum Fault in Ladakh (~ 75 km depth) and the Indian plate may penetrate as far as the Bangong Suture even the Altyn Tagh. Another one is the partial melt. We can find that there is a low-velocity-layer of shear wave in this region. Shear wave velocities are sensitive to the partial melt so that could be used to decide the presence of partial melt. They used a multiple filter technique to calculate the fundamental mode Rayleigh wave group velocity dispersion and inverted one-dimension models show a continuous low-velocity-layer from the Tethyan Himalaya to the Tibetan plateau. And the low-velocity-layer shows a good fitting with the low resistivity observation from magnetotelluric studies along the same profile. Some studies observed the temperature here is above the solidus of magma implies that probably a channel flow over there.
Reference
S. S. Rai, K. Priestley, V. K. Gaur, S. Mitra , M. P. Singh, M. Searle, 2006. Configuration of the Indian Moho beneath the NW Himalaya and Ladakh. Geophysical Research Letters, Vol. 33, L15308, 2006.
Warren B. Caldwell, Simon L. Klemperer, Shyam S. Rai, Jesse F. Lawrence, 2009. Partial melt in the upper-middle crust of the northwest Himalaya revealed by Rayleigh wave dispersion. Tectonophysic, Vol. 477, 58-65, 2009.