The SCEC Community Code Verification Exercise for Simulating Sequences of Earthquakes and Aseismic Slip (SEAS)

Brittany A. Erickson, Junle Jiang, Michael Barall, Nadia Lapusta, Eric M. Dunham, Ruth A. Harris, Lauren S. Abrahams, Kali L. Allison, Jean-Paul Ampuero, Sylvain D. Barbot, Camilla Cattania, Ahmed E. Elbanna, Yuri Fialko, Benjamin Idini, Jeremy E. Kozdon, Valere R. Lambert, Yajing Liu, Yingdi Luo, Xiao Ma, Paul Segall, Pengcheng Shi, & Meng Wei

In Preparation June 1, 2019, SCEC Contribution #9066

Numerical simulations of Sequences of Earthquakes and Aseismic Slip (SEAS) have made great progress over the past decades to address important questions in earthquake physics and fault mechanics. Significant challenges in SEAS modeling remain in resolving multiscale interactions between aseismic fault slip, earthquake nucleation, and dynamic rupture; and understanding physical factors controlling observables such as seismicity and ground deformation. The increasing capability and complexity of SEAS modeling calls for extensive efforts to verify and advance these simulations with rigor, reproducibility, and broadened impact. Over the past year, we have initiated a community code-verification exercise for SEAS simulations, supported by SCEC (the Southern California Earthquake Center). Through this exercise, we aim to develop best practices, and code-verification and simulation tools for SEAS modeling that would benefit a larger community.

Here we present code comparison results from our first benchmark, designed to test the capabilities of different computational methods in correctly solving a mathematically well-defined, basic problem in crustal faulting. This benchmark is a 2D antiplane problem, with a 1D planar vertical strike-slip fault obeying rate-and-state friction, embedded in a 2D homogeneous, linear elastic half-space. The fault has a shallow seismogenic region with velocity-weakening friction and a deeper velocity-strengthening region, below which a relative plate motion rate is imposed. A periodic sequence of spontaneous, quasi-dynamic earthquakes and slow slip are simulated in the model. We have established an online platform ( for modelers to upload and compare simulation results. The comparison of ~20 models from 11 groups using different numerical methods (FDM/FEM/BEM) show excellent general agreements. We found that domain truncation and boundary conditions strongly influence interseismic fault stressing, earthquake recurrence, and coseismic rupture speed, and that agreement between models is only achieved with sufficiently large domain sizes. Building on this initial success, we are working toward more complex scenarios involving variable event sizes, a dipping fault, and a 3D problem in our upcoming benchmarks.

Erickson, B. A., Jiang, J., Barall, M., Lapusta, N., Dunham, E. M., Harris, R. A., Abrahams, L. S., Allison, K. L., Ampuero, J., Barbot, S. D., Cattania, C., Elbanna, A. E., Fialko, Y., Idini, B., Kozdon, J. E., Lambert, V. R., Liu, Y., Luo, Y., Ma, X., Segall, P., Shi, P., & Wei, M. (2019). The SCEC Community Code Verification Exercise for Simulating Sequences of Earthquakes and Aseismic Slip (SEAS). Seismological Research Letters, (in preparation).

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