SGER: An Exploratory Study of Surface Wave Dispersion in the Indian Ocean, Indian Subcontinent and Western China

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Two of the world's first order geophysical features are found in India and its surrounding areas. First, the Himalaya and the Tibetan plateau are by far the most outstanding topography of the Earth; based on all available evidence it is known that the northward motion of the Indian subcontinent is the root cause that led to its formation. But what were the geological processes in the interior of the Earth in this area as the subcontinent plowed northward? Furthermore, in the geoidal map of the world, the Indian Ocean basin and southern India area is marked by the largest low anomaly. This geoidal low implies that there is a relative mass deficiency under the area, but at what depth and how much? Why did it form? The mechanisms that led to their formation most probably left traces in the crust and mantle under this area. A detailed mapping of the crust and upper mantle is therefore the first step toward understanding the processes. Only recently data from high quality portable seismic stations and a permanent network came into existence and data from these networks have accumulated to a degree when significant analyses can be preformed. The proposed work here will be performed in cooperation with Dr. S.S. Rai of National Geophysical Research Institute (NGRI), Hyderabad, India. We plan in the short term to use surface waves to image the lateral variations as well as resolution of upper mantle (down to ~300 km) structures. Our longer-range plan is to conduct a comprehensive surface wave tomographic study of the area.