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Unraveling earthquake dynamics through large-scale multi-physics simulations

Alice-Agnes Gabriel, Stephanie Wollherr, Thomas Ulrich, Elizabeth H. Madden, Kenneth Duru, & Duo Li

Published August 15, 2018, SCEC Contribution #8629, 2018 SCEC Annual Meeting Poster #292

Earthquakes are highly non-linear multiscale problems, encapsulating the geometry and rheology of propagating shear fractures that render the Earth’s crust and emanate destructive seismic waves.
Using physics-based earthquake scenarios, modern numerical methods and hardware specific optimizations sheds light on the dynamics, and severity, of earthquake behaviour. This is enabled by the open-source software SeisSol (www.seissol.org) that couples seismic wave propagation of high-order accuracy in space and time (minimal dispersion errors) with frictional fault failure, off-fault inelasticity and visco-elastic attenuation. SeisSol exploits unstructured tetrahedral meshes to account for complex geometries, e.g. high resolution topography and bathymetry, 3D subsurface structure, and complex fault networks. The achieved degree of realism and accuracy is enabled by recent computational optimizations targeting strong scalability on many-core CPUs and a ten-fold speedup owing to an efficient local time-stepping algorithm (Uphoff, C., Rettenberger, S., Bader, M., Madden, E.H., Ulrich, T., Wollherr, S., and A.-A. Gabriel, SC’17).

The potential of in-scale earthquake rupture simulations for augmenting earthquake source observations is demonstrated in two recent examples: i) The 2016 $M_w$7.8 Kaikoura, New Zealand earthquake, considered the most complex rupture observed to date and causing surface rupture of at least 21 segments of the Marlborough fault system. High resolution dynamic rupture modeling unravels the event's riddles in a physics-based manner (Ulrich, T., A.-A. Gabriel, J.-P. Ampuero and W. Xu, https://eartharxiv.org/aed4b/); ii) The 2004 Mw 9.1-9.3 Great Sumatra-Andaman Earthquake challenged from a lack of near-source observations. We account for complex megathrust-splay fault geometries in the largest-scale dynamic earthquake rupture simulation to date. The interplay of complex fault geometry and simple pre-stress yields good agreement of ground-deformation and long-period teleseismic data.

Lastly, we will discuss future directions for exploiting expected exascale computing infrastructure with the ExaHyPE high-performance engine for hyperbolic systems of PDEs (www.exahype.eu). Specifically, we aim to represent complex geometries with novel geometric transformations and diffuse interfaces on adaptive cartesian meshes (Duru et al., arXiv:1802.06380; Tavelli et al., arXiv:1804.09491), thus avoiding manual meshing.

Key Words
rupture dynamics, computational seismology, high-performance computing, complex fault zones, Sumatra, Kaikoura

Gabriel, A., Wollherr, S., Ulrich, T., Madden, E. H., Duru, K., & Li, D. (2018, 08). Unraveling earthquake dynamics through large-scale multi-physics simulations. Poster Presentation at 2018 SCEC Annual Meeting.

Related Projects & Working Groups
Computational Science (CS)