Testing the Presence of Fluids/Crustal Melts in the India-Asia Collision Zone Using Rayleigh Wave Dispersion Analysis
A network of 15 broadband seismographs in an approximately 500 km long, N-S array recorded 12 months of data in 2002-2003 (Rai, S S, et al., Configuration of the Indian Moho beneath the NW Himalaya and Ladakh, GRL 33). The array traverses the NW Himalaya, from the Indian plain in the south, across the Indus-Tsangpo suture and the Tso Morari Dome, to the southern flank of the Karakoram in the north. Magnetotelluric (MT) studies in this region reveal low-resistivity zones which may be indicative of fluids, graphite, or partial melts in the mid-crust. We test this hypothesis by creating 1-D models of crustal velocity structure, which should contain low-velocity zones if partial melts or fluids are present. Our models are obtained by inverting group and phase velocity dispersion curves of fundamental mode Rayleigh waves in the period range of roughly 8 to 30 s. Numerous magnitude 4 events, several magnitude 5 events, and one magnitude 6 event occurred 900 km or less from the array. Current results reveal, as expected, demonstrably different crustal structure in the Indian shield and collisional zone, and preliminary results suggest that a low-velocity zone is present in the collisional zone.
AGU Fall Meeting Abstracts
- Pub Date:
- December 2007
- 7205 Continental crust (1219);
- 7255 Surface waves and free oscillations;
- 8108 Continental tectonics: compressional