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

关于固体地球结构的准确信息来自高度不均匀的岩石圈表面记录的地震图。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同化为弹性和非弹性结构的三维模型。这些方法通过数值求解非均匀非弹性固体的运动方程，充分考虑了波的激发、传播和相互作用的物理过程。使用伴随和散射积分方法的全3D层析成像需要执行复杂的计算程序，这对最先进的高性能计算(HPC)系统提出了挑战。目前的研究是千万亿级的；未来的研究将需要亿级级能力。该项目将建立一套可互操作的社区计算平台--硬件、软件和湿件的垂直集成系统，使大量社区研究人员能够使用全3D层析成像技术来完善地球结构。两个层析成像平台将建立在高度可伸缩的代码上，用于求解正演问题：AWP-ODC四阶交错网格有限差分程序，已广泛用于区域地震模拟和基于物理的地震危险性分析；以及SPECFEM3D谱单元程序，它能够在从局部到全球的尺度上模拟基本上任意复杂的非球面结构中的波传播。第三个平台以南加州地震中心(SCEC)开发的统一社区速度模型(UCVM)软件为基础，将提供一个共同框架，用于比较和综合地球模型，并向广泛的地球科学家社区提供模型产品。这些平台将部署在NCAR-怀俄明州超级计算中心(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).