HR: 15:15h
AN: T53D-07    [Abstracts]
TI: Crustal flow in the India-Asia collision constrained by earthquakes
AU: * Androncos, C L
EM: andron@utep.edu
AF: Department of Geological Sciences, The University of Texas at El Paso, 500 W University Ave , El Paso, Tex 79968 United States
AU: Velasco, A A
EM: velasco@geo.utep.edu
AF: Department of Geological Sciences, The University of Texas at El Paso, 500 W University Ave , El Paso, Tex 79968 United States
AU: Hurtado, J M
EM: hurtado@geo.utep.edu
AF: Department of Geological Sciences, The University of Texas at El Paso, 500 W University Ave , El Paso, Tex 79968 United States
AB: Continent-continent collision is one of the fundamental processes in the plate tectonic cycle and is critical to understanding crustal evolution. The India-Asia collision provides the opportunity to investigate the mechanics of continent-continent collision in a modern setting avoiding many of the uncertainties inherent in studying ancient mountain belts. A fundamental problem in understanding the India-Asia collision is what drives deformation in the Tibetan Plateau. Seismic activity provides one of the best constraints on the stresses responsible for mountain building and how that stress is distributed. We have examined earthquakes distributed throughout the Indian foreland, the Greater Himalaya and the Tibetan Plateau. We focus on earthquakes with well-controlled depths, and use the Harvard Centroid Moment Tensor (CMT) catalog to map brittle deformation and stress orientations in the region. We find that deep earthquakes within the Indian Plate dip beneath an aseismic wedge. This aseismic wedge extends north from beneath the Himalaya to the Tibetan Plateau. In most of Tibet earthquakes are restricted to the upper 35 km of the crust until the Kunlun fault is reached. At the Kunlun fault seismicity extends to depths as great as 50 km. The region between the Himalaya and the Kunlun fault deforms by transtension. This coincidence of transtension with a thick aseismic lower crust is consistent with the lower crust beneath Tibet deforming as a plastically flowing channel.
DE: 8010 Fractures and faults
DE: 8102 Continental contractional orogenic belts
SC: Tectonophysics [T]
MN: 2004 AGU Fall Meeting