Department of Civil and Environmental Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801.
Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, IL 61801.
Proc Natl Acad Sci U S A. 2021 May 11;118(19). doi: 10.1073/pnas.2025632118.
Tsunami generation from earthquake-induced seafloor deformations has long been recognized as a major hazard to coastal areas. Strike-slip faulting has generally been considered insufficient for triggering large tsunamis, except through the generation of submarine landslides. Herein, we demonstrate that ground motions due to strike-slip earthquakes can contribute to the generation of large tsunamis (>1 m), under rather generic conditions. To this end, we developed a computational framework that integrates models for earthquake rupture dynamics with models of tsunami generation and propagation. The three-dimensional time-dependent vertical and horizontal ground motions from spontaneous dynamic rupture models are used to drive boundary motions in the tsunami model. Our results suggest that supershear ruptures propagating along strike-slip faults, traversing narrow and shallow bays, are prime candidates for tsunami generation. We show that dynamic focusing and the large horizontal displacements, characteristic of strike-slip earthquakes on long faults, are critical drivers for the tsunami hazard. These findings point to intrinsic mechanisms for sizable tsunami generation by strike-slip faulting, which do not require complex seismic sources, landslides, or complicated bathymetry. Furthermore, our model identifies three distinct phases in the tsunamic motion, an instantaneous dynamic phase, a lagging coseismic phase, and a postseismic phase, each of which may affect coastal areas differently. We conclude that near-source tsunami hazards and risk from strike-slip faulting need to be re-evaluated.
地震引起的海底变形产生的海啸一直被认为是沿海地区的主要灾害。走滑断层通常被认为不足以引发大型海啸,除非引发海底滑坡。在此,我们证明了走滑地震产生的地面运动在相当普遍的条件下有助于产生大型海啸(>1 米)。为此,我们开发了一个计算框架,该框架将地震破裂动力学模型与海啸生成和传播模型集成在一起。从自发动态破裂模型得出的三维时变垂直和水平地面运动用于驱动海啸模型中的边界运动。我们的结果表明,沿走滑断层传播的超剪切破裂,穿过狭窄而浅的海湾,是产生海啸的主要候选者。我们表明,动态聚焦和走滑地震的大水平位移,是长断层上走滑地震的特征,是海啸灾害的关键驱动因素。这些发现指出了走滑断层产生大量海啸的内在机制,而不需要复杂的震源、滑坡或复杂的水深。此外,我们的模型确定了海啸运动中的三个不同阶段,即瞬时动力阶段、滞后同震阶段和震后阶段,每个阶段都可能对沿海地区产生不同的影响。我们得出结论,需要重新评估走滑断层的近源海啸灾害和风险。