Research Interests

As a geologist and geophysicist, I am interested in the processes and forces responsible for deformation of the Earth's crust. In conjunction with my colleague Mark Zoback, I developed methodologies for determining the present-day distribution of forces in the earth's crust from a wide array of geologic and seismologic information in combination with analysis of downhole data from wells. This work demonstrated that broad regions of the Earth's crust in the United States were subjected to a uniformly oriented stress field which was relatively constant with depth and resulted from large-scale tectonic processes. Later, in collaboration with 40 scientists from 30 different countries, I extended the stress data compilation to the entire globe and found that broad regions (with dimensions of more than 1000 km in some cases) within the tectonic plates forming the Earth's outer shell were subjected to a relatively uniform stress field, both in magnitude and orientation. We demonstrated that these broad-scale "first-order" stress regimes could be predicted from the geometry of the plate and broad-scale compressional forces driving plate motion. In addition, we showed that local perturbations to the regional stresses ("second-order stresses") could be explained by superimposed stresses related to plate flexure or gravitational potential energy derived from lateral variations in density. The amount of local stress rotation was used to constrain the relative magnitude of the local stress compared to the regional stress. The stress data and understandings gained from this global study have been applied to a wide array of studies from seismic hazard analysis to constraining mantle convection.

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Primary Section

Section 15: Geology

Secondary Section

Section 16: Geophysics