Large-scale Northridge Earthquake Simulation Using Octree-based Multiresolution Mesh Method

Large scale ground motion simulation in realistic basins can benefit greatly from the use of parallel supercomputing systems in order to obtain reliable and useful results within reasonable elapsed time due to its large problem size. We present a parallel octree-based multiresolution finite element methodology for the elastodynamic wave propagation problem and develop a framework for large scale wave propagation simulations. The framework is comprised of three parts; (1) a mesh generator (Euclid, Tu et al. 2002), (2) a parallel mesh partitioner (ParMETIS, Karypis et al. 2002), and (3) a parallel octree-based multiresolution finite element solver (QUAKE, Kim 2003). The octree-based multiresolution finite element method reduces memory use significantly and improves overall computational performance. The numerical methodology and the framework have been used to simulate the seismic response of the greater Los Angeles basin for a mainshock of the 1994 Northridge Earthquake, for frequencies of up to 1 Hz and domain size of 80 80 30 km . Through simulations for several models, ranging in size from 400,000 to 300 million degrees of freedom on the 3000-processors HP-Compaq AlphaServer Cluster at the Pittsburgh Supercomputing Center (PSC), we achieve excellent performance and scalability.