Ground Motion Simulation
Associate Professor Brendon Bradley (UC)
Rob Graves (USGS, Pasadena)
Robin Lee, Ethan Thomson (UC PhD students)
Tony Dale, Sung Bae (UC HPC)
The 2010-2011 Christchurch earthquakes produced severe ground motions, significant ground failure and structural damage. Such damage from relatively small magnitude earthquakes in the near-source region provides significant motivation to better understand the salient physical phenomena associated with the earthquake rupture, 3D wave propagation and the nonlinear response of potentially liquefiable soils in these events, and thus the likelihood of repeat occurrences in Christchurch, New Zealand, and internationally.
This study is utilizing UC’s BlueGeneP supercomputer to perform highly parallelized 3D earthquake wave propagation simulations of the major earthquakes in the 2010-2011 Canterbury sequence and major earthquakes that are expected to occur in New Zealand in the future. The simulation source code was developed by collaborater Rob Graves (USGS, Pasadena) and utilizes 4th order spatial and 2nd order temporal finite differences to solve the elastodynamic wave equation.
Typical simulations performed for the 2010-2011 earthquakes in the Canterbury region (a 3D model of dimensions 140x120x50 km3, using 840 Million finite difference grid points) require approximately 4 hours of wall clock time with 2048 cores on BlueGeneP (approximately 8000 core hours). However, the simulation source code is highly scalable within the BlueGeneP architecture. We have also performed a prototype simulation of the ground shaking from a magnitude M7.9 earthquake on the Alpine Fault over the entire South Island region (a 3D model with dimensions 800x300x100 km3, using 24 Billion grid points) which required approximately 4 days of computation on the full 8192 cores of UC’s BlueGene P (approximately 800,000 core hours).
The two animations below illustrate the peak velocity at the ground surface during the 4 September 2010 Darfield and 22 February 2011 Christchurch earthquakes .