Using New Constraints on Stress and Strength in Dynamic Rupture Models of the M 9.1-9.3 2004 Sumatra-Andaman Earthquake
Abstract
The influence of the initial stress, friction and fault geometry on earthquake rupture propagation has been shown in numerous studies. However, getting these conditions right for specific earthquakes remains a challenge. In addition, the close relationships between fault geometry, strength and tractions makes their unique determination difficult. Here, we present a series of 3D dynamic ruptures along the plate interface that hosted the 2004 M 9.1-9.3 Sumatra-Andaman earthquake. First, we constrain initial absolute stresses, dynamic strength and rock composition using a 2D seismo-thermo-mechanical (STM) model simulating the long-term earthquake cycle at the latitude of the earthquake's hypocenter. Slip instabilities that approximate earthquakes arise spontaneously in the STM model at different locations along the subduction zone interface. Thus, the STM model produces a range of initial conditions that are used to model several dynamic rupture events along the megathrust. The dynamic rupture models are performed with SeisSol, a software package based on an ADER-Discontinuous Galerkin scheme for solving the dynamic fault rupture and wave propagation problems with high-order accuracy in space and time. Use of an unstructured tetrahedral mesh allows for a realistic representation of the non-planar slab interface and bathymetry. The results emphasize the influence of stress and strength on rupture extent and propagation speed. Second, we fix the input parameters as those that best re-produce the earthquake's hypocentral location, magnitude, speed, and rupture extent along strike, but incorporate more complex fault geometry. The 30 m tsunami wave height reported near northern Sumatra suggests slip on landward and possibly also seaward dipping splay faults near the epicenter. This is supported by forethrust and backthrust imaging and mapping from deep seismic reflection surveys, bathymetric data and relocated seismicity. Rupture propagation and final surface displacements for models with different splay fault geometries are compared. This comparison is critical to future work to couple the dynamic rupture output from these models with tsunami wave propagation models in the context of the ASCETE project, "Advanced Simulation of Coupled Earthquake and Tsunami Events".
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2016
- Bibcode:
- 2016AGUFM.S21B2725M
- Keywords:
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- 7209 Earthquake dynamics;
- SEISMOLOGYDE: 7215 Earthquake source observations;
- SEISMOLOGYDE: 8118 Dynamics and mechanics of faulting;
- TECTONOPHYSICSDE: 8163 Rheology and friction of fault zones;
- TECTONOPHYSICS