Geodetic constraints on earthquake source parameters and continental deformation in India and Tibet

The studies contained herein are divided into two groups. First, I devise methods for combining historical data from the Great Trigonometrical Survey of India (GTS) with Global Positioning System (GPS) data to determine rupture parameters of two large Indian earthquakes and quantify intraplate deformation on rift basins in western India. I confirm that the Mw 7.6 Bhuj 2001 earthquake was a high stress-drop event on a relatively small rupture (25 km x 15 km); the region may suffer future similar earthquakes. With the same methods, I provide weak constraints on the rupture of the Mw 7.8 Kangra 1905 earthquake and prove that previous interpretations of a rupture length of >200 km are incorrect, and a large segment of the plate boundary may rupture in future major events. I also attempt to quantify strain over long baselines that span paleorifts in western India. While the GTS data reveal apparent shortening across the Kachchh and Narmada Rifts, GPS velocities show there is little relative motion across the rifts; the GTS data are likely contaminated by errors.; Second, I examine the continental deformation of Tibet in two different studies. To address the question of whether Tibet is best described as a continuum of regionally distributed deformation or a series of rigid blocks bounded by large, quickly slipping fault systems, I measure a GPS profile across the Altyn Tagh strike-slip fault. The results confirm a slip rate of 9+/-4 mm/yr, consistent with other geodetic estimates and supporting the description of Tibet as a continuum in which most of the India-Asia collision is accommodated by regionally distributed deformation. Finally, I examine the rheology and strength of the lithosphere by considering the deformation field around the eastern Himalayan syntaxis in the context of the thin viscous sheet deformation model. The Moho temperature beneath Tibet must be 75°-200°C warmer than beneath Eurasia to reproduce the observed deformation field, and the rheology is consistent with deformation that is limited by the strength of the viscous upper mantle rather than that of the brittle, faulted upper crust.