Wedge plasticity and coupled simulations of dynamic rupture and tsunami in the Cascadia subduction zone

Andrew Wilson, & Shuo Ma

Published August 9, 2019, SCEC Contribution #9407, 2019 SCEC Annual Meeting Poster #188

In an elastic dislocation model, whether or not a subduction plate boundary fault breaks the trench has a significant effect on seafloor deformation and resulting tsunami. However, when inelastic deformation of the sedimentary wedge is considered, this boundary condition is less important because large seafloor uplift can occur with little or no slip at the trench (Ma, 2012; Ma and Hirakawa, 2013). Several seismic profiles along the Cascadia subduction zone indicate that the subduction megathrust is buried by thick sediments and does not reach the trench. Lotto et al. (2018) carried out coupled dynamic rupture and tsunami simulations for a buried fault in Cascadia, incorporating realistic fault geometry, bathymetry, and velocity structure, assuming elastic dislocation. Here we extend that model by incorporating wedge plasticity. Our coupled models of dynamic rupture and tsunami show that the large amount of sediments in this accretionary prism significantly contribute to seafloor uplift and produce tsunami heights that can be twice or more as large as in purely elastic simulations, while also producing weaker acoustic waves in the ocean. Wedge plasticity plays an important role for tsunami generation in the Cascadia subduction zone, and likely for other sediment-filled subduction margins as well.

Key Words
tsunami, Cascadia, dynamic rupture, inelastic, coupled, finite element

Citation
Wilson, A., & Ma, S. (2019, 08). Wedge plasticity and coupled simulations of dynamic rupture and tsunami in the Cascadia subduction zone. Poster Presentation at 2019 SCEC Annual Meeting.

Related Projects & Working Groups
Fault and Rupture Mechanics (FARM)