Topography effects in the near field for a dislocation point source: A comparison of the FEM-HERCULES code and the 3D IBEM

Edilson F. Salazar Monroy, Leonardo Ramirez-Guzman, Marcial Contreras-Zazueta, & Francisco J. Sanchez-Sesma

Submitted August 15, 2016, SCEC Contribution #6888, 2016 SCEC Annual Meeting Poster #295

We analyze a staircase and slope-dependant meshing strategy for modeling topographical features using the HERCULES finite element toolchain (Tu et al., 2006). We compare the Finite Element solution against the Integral Boundary Element Results using an ellipsoidal Gaussian shape as a benchmark and an irregularity of the free boundary in an elastic half-space, subjected to incident waves generated by a dislocation. The staircase approach analyzed here is based on a slope-dependent variable mesh which we tailored to follow the free surface, naturally fulfilling the free boundary condition. The IBEM, our reference solution, is based on an integral representation of auxiliary force densities. This approach allows low-cost and accurate computations for 3D configurations, as we only discretized the free boundary and used Stokes' analytical solution for the Green’s function of the full elastic space. Our cross-verification uses ground motions computed at the free surface using both numerical schemes. The results indicate that elements with an average of 10 to 12 points per wavelength, together with a few smaller ones, provide accurate solutions when a low-pass filter is applied to remove high frequencies associated with spurious eigenvalues of the discretized dynamic system. Finally, we discuss advantages and limitations of these numerical approaches.

Key Words
Ground Motion Simulation, Finite Element Method, Integral Boundary Element, Numerical Modeling

Citation
Salazar Monroy, E. F., Ramirez-Guzman, L., Contreras-Zazueta, M., & Sanchez-Sesma, F. J. (2016, 08). Topography effects in the near field for a dislocation point source: A comparison of the FEM-HERCULES code and the 3D IBEM. Poster Presentation at 2016 SCEC Annual Meeting.


Related Projects & Working Groups
Ground Motion Simulation Validation (GMSV)