Summit and Theta are two of the newest, most powerful high-performance computers in the U.S.

SCEC is a leader in research that integrates science results and new technologies into broad impact products to improve seismic hazard assessment. For instance, by designing and building CyberShake, our physics-based probabilistic seismic hazard analysis (PSHA) software, we have redefined the state of the art for understanding and anticipating low-frequency (0–1 Hz) strong motions across most of California. We continue to take our SCEC physics-based computational software, including CyberShake, to the next level by extending its capabilities to resolve shaking estimates and related uncertainties across a broadband range of frequencies of engineering interest (i.e., 0–20 Hz). We conduct research as we implement new physical models and tools into software, and regularly validate our results against empirical datasets. 

To conduct this research and run CyberShake require extensive compute time on high-performance computers (HPC). SCEC obtains time to run on some of the largest systems in the world by a process of competitive proposals to various programs from DOE and NSF. The proposals are evaluated for their scientific merit as well as for the ability of the software team to carry out computations on these highly complex machines. Our research teams have been successful in obtaining time on two Department of Energy systems: 300,000 node-hours on Summit and 500,000 node-hours on Theta for 2020. It’s difficult to make sense of these large numbers, but it’s about the equivalent of running on your laptop for 1100 years. That’s a lot of compute power to the service of SCEC research. And we’ll use it all! 

Summit, at the Oak Ridge National Laboratory in Oak Ridge, Tennessee, is the world’s largest open-science supercomputer.  In the year Summit has been available, SCEC researchers have used it to run the CyberShake platform, perform large-scale wave propagation simulations, and integrate topography, small-scale crustal velocity perturbations and nonlinear effects (see Figure below) into our codes.

Theta, at the Argonne National Laboratory outside of Chicago, contains more than 280,000 cores.  Using Theta, SCEC researchers performed dynamic rupture simulations incorporating complex fault geometry and roughness, improving the accuracy of the models. Link to Argonne’s story: https://www.alcf.anl.gov/science/projects/extreme-scale-simulations-advanced-seismic-ground-motion-and-hazard-modeling

Example of large-scale simulations including advanced nonlinear material behavior (Roten et al. 2019). We implemented the parallel-series nonlinear (hysteretic) Iwan model into the scalable finite-difference code AWP-ODC, and used the code to model a M7.8 ShakeOut-type scenario on the southern San Andreas fault. Comparison of (left) linear and (right) nonlinear ground motion simulations show a significant reduction in spectral accelerations at 3s (3s-SAs) near the fault and at station rus, where waveguide focusing is amplifying the waves radiated from the SAF. The nonlinear simulation results are in better agreement with empirical ground motion models than those from the linear simulation. 

References 

Roten, D., K.B. Olsen, and S. M. Day (2019). 3D Simulation of Large San Andreas Scenario Earthquakes Using a Multi-Surface Plasticity Model, Seism. Res. Lett. 90, 2B, 943.

Roten, D., Olsen, K. B., Day, S. M., & Cui, Y. (2019, 08). An Iwan-type Plasticity Model for 3D Simulations of San Andreas Scenario Earthquakes. Poster Presentation at 2019 SCEC Annual Meeting.