My research focus is theoretical & computational seismology. The quality of tomographic images of the Earth's interior is closely tied to our ability to efficiently and accurately simulate 3-D seismic wave propagation on global, regional, and local scales. For decades seismologists have attempted to use asymptotic and numerical methods to address the forward problem in seismology, i.e., given a 3-D Earth model, accurately simulate the associated ground motions. In collaboration with Dmitry Komatitsch at the University of Pau, we have facilitated simulations of 3-D acoustic, (an)elastic, and poroelastic wave propagation at unprecedented resolution and accuracy by taking advantage of modern numerical methods and harnessing parallel computers. As a result of our efforts, on a modest PC cluster one can now simulate 3-D global seismic wave propagation at periods of 20 s and longer, accounting for heterogeneity in the crust and mantle, topography, anisotropy, attenuation, fluid-solid interactions, self-gravitation, rotation, and the oceans. On the next generation petaflops machines we will able to reach a shortest period of 1 s in global simulations. The challenge now lies in harnessing these new found forward modeling capabilities to enhance the quality of images of Earth's interior and the earthquake rupture process, i.e., to address the seismological inverse problem. Our current research efforts are focused on using adjoint methods to 'image' earth structure on all scales.
