Earthquake Rupture on Multiple Splay Faults and Its Effect on Tsunamis
van Zelst, I.; Rannabauer, L.; Gabriel, A.-A.; van Dinther, Y.
(2022) Journal of Geophysical Research: Solid Earth, volume 127, issue 8, pp. 1 - 20
(Article)
Abstract
Detailed imaging of accretionary wedges reveals splay fault networks that could pose a significant tsunami hazard. However, the dynamics of multiple splay fault activation during megathrust earthquakes and the consequent effects on tsunami generation are not well understood. We use a 2-D dynamic rupture model with complex topo-bathymetry and six
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curved splay fault geometries constrained from realistic tectonic loading modeled by a geodynamic seismic cycle model with consistent initial stress and strength conditions. We find that all splay faults rupture coseismically. While the largest splay fault slips due to a complex rupture branching process from the megathrust, all other splay faults are activated either top down or bottom up by dynamic stress transfer induced by trapped seismic waves. We ascribe these differences to local non-optimal fault orientations and variable along-dip strength excess. Generally, rupture on splay faults is facilitated by their favorable stress orientations and low strength excess as a result of high pore-fluid pressures. The ensuing tsunami modeled with non-linear 1-D shallow water equations consists of one high-amplitude crest related to rupture on the longest splay fault and a second broader wave packet resulting from slip on the other faults. This results in two episodes of flooding and a larger run-up distance than the single long-wavelength (300 km) tsunami sourced by the megathrust-only rupture. Since splay fault activation is determined by both variable stress and strength conditions and dynamic activation, considering both tectonic and earthquake processes is relevant for understanding tsunamigenesis.
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Keywords: dynamic rupture, earthquake, numerical modeling, splay fault, subduction zone, tsunami, Geophysics, Geochemistry and Petrology, Earth and Planetary Sciences (miscellaneous), Space and Planetary Science
ISSN: 2169-9313
Note: Funding Information: The authors would like to thank the Editor Satoshi Ide, the anonymous Associate Editor, and two reviewers. From a previous submission to GRL, the authors would like to thank the Editor Germán Prieto, the Associate Editor Victor Tsai, reviewer Kenny Ryan, and an anonymous reviewer. Their feedback has greatly helped to shape and improve this work. The authors warmly thank Stephanie Wollherr, Thomas Ulrich, Casper Pranger, Luca Dal Zilio, and Andreas Fichtner for sharing their expertise on the SC and DR models. The authors also thank the Tectonics Group at the University of Leeds for helpful comments and discussion that improved this manuscript. The authors are much obliged to Sebastian Rettenberger, who originally wrote the tsunami code. The authors use scientific color maps by Crameri ( 2018b ) to prevent visual distortion of the data and exclusion of readers with color‐vision deficiencies (Crameri, 2018a ). The authors used the computational resources of the ETH cluster Euler. This work was part of the ASCETE‐II project (Advanced Simulation of Coupled Earthquake‐Tsunami Events) funded by the Volkswagen Foundation Grant 88479. Additionally, I. van Zelst was funded by the Royal Society (UK) through Research Fellows Enhancement Award RGF\EA\181084. I. van Zelst also acknowledges the financial support and endorsement from the DLR Management Board Young Research Group Leader Program and the Executive Board Member for Space Research and Technology. A.‐A. Gabriel acknowledges support from the European Union's Horizon 2020 Research and Innovation Program (TEAR ERC Starting Grant No. 852992; ChEESE project, Grant Agreement No. 823844), the German Research Foundation (DFG) (projects GA 2465/2‐1 and GA 2465/3‐1), and the National Science Foundation (NSF; Grant No. EAR‐2121666). Open Access funding enabled and organized by Projekt DEAL. Funding Information: The authors would like to thank the Editor Satoshi Ide, the anonymous Associate Editor, and two reviewers. From a previous submission to GRL, the authors would like to thank the Editor Germán Prieto, the Associate Editor Victor Tsai, reviewer Kenny Ryan, and an anonymous reviewer. Their feedback has greatly helped to shape and improve this work. The authors warmly thank Stephanie Wollherr, Thomas Ulrich, Casper Pranger, Luca Dal Zilio, and Andreas Fichtner for sharing their expertise on the SC and DR models. The authors also thank the Tectonics Group at the University of Leeds for helpful comments and discussion that improved this manuscript. The authors are much obliged to Sebastian Rettenberger, who originally wrote the tsunami code. The authors use scientific color maps by Crameri (2018b) to prevent visual distortion of the data and exclusion of readers with color-vision deficiencies (Crameri, 2018a). The authors used the computational resources of the ETH cluster Euler. This work was part of the ASCETE-II project (Advanced Simulation of Coupled Earthquake-Tsunami Events) funded by the Volkswagen Foundation Grant 88479. Additionally, I. van Zelst was funded by the Royal Society (UK) through Research Fellows Enhancement Award RGF\EA\181084. I. van Zelst also acknowledges the financial support and endorsement from the DLR Management Board Young Research Group Leader Program and the Executive Board Member for Space Research and Technology. A.-A. Gabriel acknowledges support from the European Union's Horizon 2020 Research and Innovation Program (TEAR ERC Starting Grant No. 852992; ChEESE project, Grant Agreement No. 823844), the German Research Foundation (DFG) (projects GA 2465/2-1 and GA 2465/3-1), and the National Science Foundation (NSF; Grant No. EAR-2121666). Open Access funding enabled and organized by Projekt DEAL. Publisher Copyright: © 2022. The Authors.
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