Crustal stress estimation in the Himalayan wedge
Quantitative estimates of crustal stress magnitude and orientation are hard to come by. On the other hand, geodesy is providing an increasingly accurate picture of global tectonic motions. Field and laboratory analyses contribute fault slip rates and exhumation rates. Seismology yields estimates of stress from moment tensor analyses. I am working to combine these data sources with geometrically accurate elastic boundary element models to estimate the crustal stress field and the driving forces behind those stresses – for example, mantle tractions on the base of the crust.
Currently, I am applying these methods to the Himalayan wedge in the vicinity of the 2015 Nepal earthquake. In the past, Coulomb wedge and elastic wedge models provided a qualitative picture of these stresses and the growth of mountain belts over long time scales. My work will make these models quantitative by constraining geometrically realistic wedge models with geodetic and geologic observations. An improved image of the stress in the crust will help answer several questions about active tectonics in the Himalayas. Are stress drops low or high compared to total stress? Is it reasonable that some stress in the Himalayas might be released as plastic strain rather than fault slip? What fault slip rates and directions are consistent with different hypotheses concerning the tectonic driving forces?
Principal stress orientations in a cross section of the Himalayan wedge including a frictional detachment and one internal MCT-like fault.