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.