SCEC Award Number 19128 View PDF
Proposal Category Individual Proposal (Integration and Theory)
Proposal Title Development and Optimization of Iwan Model in Discontinuous Mesh Finite Difference Code AWP-ODC-GPU
Investigator(s)
Name Organization
Daniel Roten San Diego State University Kim Olsen San Diego State University Steven Day San Diego State University Yifeng Cui University of California, San Diego
Other Participants
SCEC Priorities 4a, 4b, 4c SCEC Groups GM, CS, Seismology
Report Due Date 04/30/2020 Date Report Submitted 06/10/2020
Project Abstract
 The scope of SCEC project 19128 was to finalize the implementation of Iwan-type nonlinearity in the discontinuous mesh finite difference code AWP-ODC-DM. The long-term goal of the re- search is to capture the hysteretic stress-strain relationship in shallow sediments in high-resolution 3D finite difference simulations of strong shaking. The Iwan model method had already been im- plemented in the computationally less efficient CPU version of AWP-CPU-Iwan during previous SCEC-funded projects, and its accuracy has been verified against independent nonlinear 1D and 2D wave propagation code. In this project, the implementation of the main Iwan stress and velocity update kernels in AWP-GPU-DM was completed. Using simple 1D site response benchmarks, the accuracy of these routines was verified against the CPU version of AWP and independent codes. Several algorithmic changes were required with respect to the implementation in AWP-CPU-Iwan to preserve the computational and memory efficiency of the GPU code.
Intellectual Merit This project directly addresses the question of how strong ground motions depend on the complexities and nonlinearities of earthquake systems, one of the five basic questions outlined in
SCEC5. Implementation of realistic soil nonlinearity into the efficient, discontinuous mesh finite difference code provides the community with a powerful tool to model the dynamics of the source, wave propagation and site response in a single step. The performed research aligns with SCEC5's goal to depart from an isolated treatment of source, site and path effects, and to consider surface ground motions as the nonlinear response of soils and rocks from source to surface.
Broader Impacts The scenario of a large earthquake on the southern San Andreas fault dominates the hazard for high-rise buildings in the Los Angeles region. Our result show that more accurate predictions of long-period ground motions during such event can be simulated with advanced plasticity models. Ongoing research aims to include such nonlinear effects in the Cybershake simulations, which will result in more accurate physics-based seismic hazard maps.
Exemplary Figure Figure 2: Surface velocity time series at KiK-net site KSRH10 obtained from Iwan-type nonlinear simulation using the GPU and CPU versions of AWP. The linear solution is shown for reference. Nonlinear predictions using the Iwan model were obtained using 10 yield surfaces.