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

关于固体地球结构的精确信息来自于在高度不均匀的岩石圈表面记录的地震记录。基于伴随和散射积分方法的全三维层析成像可以将这些信息吸收到弹性和非弹性结构的三维模型中。这些方法通过数值求解非均匀非弹性固体的非齐次运动方程，充分解释了波的激发、传播和相互作用的物理性质。使用伴随和散射积分方法的全三维断层扫描需要执行复杂的计算程序，这对最先进的高性能计算（HPC）系统构成了挑战。目前的研究是千万亿次；未来的研究将需要百亿亿级的能力。这个项目将建立一套可互操作的社区计算平台。垂直集成的硬件、软件和湿软件系统，将允许一个重要的研究社区使用全3d断层扫描技术来细化地球结构。两个层析成像平台将建立在高度可扩展的代码上，用于解决正演问题：AWP-ODC四阶，交错网格，有限差分代码，已广泛用于区域地震模拟和基于物理的地震危害分析，以及SPECFEM3D谱元代码，能够在从局部到全球的尺度上模拟波通过本质上任意复杂性的非球面结构的传播。第三个平台，基于南加州地震中心（SCEC）开发的统一社区速度模型（UCVM）软件，将提供一个通用框架，用于比较和综合地球模型，并将模型产品交付给广泛的地球科学家社区。这些平台将部署在NCAR-Wyoming超级计算中心（NWSC）。

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).