An OpenMP Approach to Modeling Dynamic Earthquake Rupture Along Geometrically Complex Faults on CMP Systems.
ABSTRACT Chip multiprocessors (CMP) are widely used for high performance computing and are being configured in a hierarchical manner to compose a CMP compute node in a parallel system. OpenMP parallel programming within such a CMP node can take advantage of the globally shared address space and on-chip high inter-core bandwidth and low inter-core latency. In this paper, we use OpenMP to parallelize a sequential earthquake simulation code for modeling spontaneous dynamic earthquake rupture along geometrically complex faults on two CMP systems, IBM POWER5+ system and SUN Opteron server. The experimental results indicate that the OpenMP implementation has the accurate output results and the good scalability on the two CMP systems. Further, we apply the optimization techniques such as large page and processor binding to the OpenMP implementation to achieve up to 7.05% performance improvement on the CMP systems without any code modification.
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ABSTRACT: 1] Motivated by observations in the 2008 M w 7.9 Wenchuan earthquake, we study effects of systematic changes in the principal stress orientation along the fault strike on rupture dynamics and ground motion using a 3‐D finite‐element method. Based on Anderson's theory of faulting, we set up the initial stress field with rotations in stress orientations along strike for a dynamic rupture model of a shallow dipping fault. We find that initial stress rotations along strike can cause dramatic changes in rupture speed and produce distinct patterns in slip distribution and peak ground motion. When a mismatch (unfavorable for faulting) between fault geometry and initial stress orientations is encountered, rupture can spontaneously stop. Some first‐order features in the Wenchuan event may be partially caused by rotations in the principal stress orientation along strike, such as the rupture arrest at the northeast end and two severe destruction zones in the observed seismic intensity distribution. These results may have important implications for assessing seismic hazards imposed by faults with changes in the initial stress field along strike worldwide. Citation: Duan, B. (2010), Role of initial stress rotations in rupture dynamics and ground motion: A case study with implications for the Wenchuan earthquake, J. Geophys. Res., 115, B05301, doi:10.1029/2009JB006750.Journal of Geophysical Research Atmospheres 01/2010; 115. · 3.44 Impact Factor
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ABSTRACT:  Using a hybrid MPI/OpenMP parallel finite element method for spontaneous rupture and seismic wave propagation simulations, we investigate features in rupture propagation, slip distribution, seismic radiation, and seafloor deformation of the 2011 Mw 9.0 Tohoku-Oki earthquake to gain physical insights into the event. With simplified shallow dipping (10°) planar fault geometry, 1D velocity structure, and a slip-weakening friction law, we primarily investigate initial stress and strength conditions that can produce rupture and seismic radiation characteristics of the event revealed by kinematic inversions, and seafloor displacements observed near the epicenter. By a large suite of numerical experiments aided by parallel computing on modern supercomputers, we find that a seamount of a dimension of ∼70 km by 23 km just updip of the hypocenter on the subducting plane, parameterized by higher static friction, lower pore fluid pressure, and higher initial stress than surrounding regions, may play a dominant role in the 2011 event. Its high strength stalls updip rupture for tens of seconds, and its high stress drop generates large slip. Its failure drives the rupture to propagate into the shallow portion that is likely velocity-strengthening, resulting in significant slip near the trench within a limited area. However, the preferred model suggests that the largest slip in the event occurs near the hypocenter. High-strength patches along the downdip portion of the subducting plane are most effective among several possible factors in generating high-frequency seismic radiations, suggesting the initial strength distribution there is very heterogeneous.Journal of Geophysical Research Atmospheres 01/2012; 117:05311. · 3.44 Impact Factor