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Dynamic Earthquake Rupture Simulations with SeisSol

Within the ASCETE project we will investigate in Tsunamis caused by Earthquakes. To this end, a fundamental understanding of the earthquake rupture propagation is important as the resulting ocean bottom displacement causes the corresponding sea level disturbance and, thus, the potential generation of a tsunami. Therefore, a strong emphasis of the ASCETE project is on the development of advanced earthquake simulators that have the potential to answer basis key questions of earthquake physics. Of particular interest is rupture propagation on complex fault geometries, e.g.

  • on rough fault surfaces that radiate high frequency waves,
  • on subduction faults with shallow dip angles in combination with splay faults,
  • and the interaction of those faults with the free surface or bathymetry.

The geometrical complexity of the geological settings lead to high requirements for available modeling tools. Other challenges are to solve the underlying mathematical problem of the earthquake faulting and the subsequent seismic wave propagation with high accuracy under realistic conditions. Especially the faulting process or frictional sliding can lead to spurious unphysical oscillations in the numerical solutions.

The ASCETE project will focus on the software package SeisSol. SeisSol is a high-order accurate Discontinuous Galerkin (ADER-DG) solver implemented on unstructured tetrahedral meshes. The use of tetrahedral elements simplifies the model generation process and is capable to include complex geometries. A further unique advantage is that the ADER-DG scheme does not produce any artificial noise neither during the rupture process nor during the wave propagation. This way, the dynamic rupture process as well as the seismic wave propagation can be modeled with the same tool while keeping numerical errors as low as possible.

Previous publications (de la Puente et al. 2009, Pelties et al. 2012) show SeisSol’s advantages incorporating complex fault geometries like the Landers ‘92 fault system (see figures). During the project duration we will port the framework to subduction earthquake faults including splay faults that can potentially cause tsunamis.

Illustration of a complex three-dimensional fault system (vertical planes) inspired by the Landers fault system that ruptured in 1992 with a magnitude of 7.2. The fault is discretized by a fine triangular grid in order to resolve the fault physics accurately. With increasing distance to the fault mesh coarsening is applied to save computational costs as the wave propagation allows for larger elements.
Illustration of a complex three-dimensional fault system
Development of the ground velocity field with time. The topography is scaled by a factor of 3. v represents the absolute particle velocity in m/s. The viewing direction is roughly from southeast to northwest. A directivity effect can be clearly observed.
Development of the ground velocity field with time
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