Community Computational Platforms for Developing Three-Dimensional Models of Earth Structure

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Precise information about the structure of the solid Earth comes from seismograms recordedat the surface of a highly heterogeneous lithosphere. Full-3D tomography based on adjoint andscattering-integral methods can assimilate this information into three-dimensional models of elastic andanelastic structure. These methods fully account for the physics of wave excitation, propagation, andinteraction by numerically solving the inhomogeneous equations of motion for a heterogeneous anelasticsolid. Full-3D tomography using adjoint and scattering-integral methods requires the execution ofcomplex computational procedures that challenge the most advanced high-performance computing(HPC) systems. Current research is petascale; future research will require exascale capabilities. This project will establish an interoperable set of community computational platforms?verticallyintegrated systems of hardware, software, and wetware that will allow a significant community ofinvestigators to employ the techniques of full-3D tomography to refine Earth structures. Two tomographicplatforms will be built on highly scalable codes for solving the forward problem: the AWP-ODC 4th-order,staggered-grid, finite-difference code, which has been widely used for regional earthquake simulation andphysics-based seismic hazard analysis, and the SPECFEM3D spectral element code, which is capable of modeling wave propagation through aspherical structures of essentially arbitrary complexity on scales ranging from local to global. A third platform, based on the Unified Community Velocity Model (UCVM) software developed by the Southern California Earthquake Center (SCEC), will provide a common framework for comparing and synthesizing Earth models and delivering model products to a wide community of geoscientists. These platforms will be deployed at the NCAR-Wyoming Supercomputing Center (NWSC).