Ground Motion Characteristics of Subshear and Supershear Ruptures in the Presence of Sediment Layers

Mohamed Abdelmeguid, Ahmed E. Elbanna, & Ares J. Rosakis

Published September 8, 2024, SCEC Contribution #13950, 2024 SCEC Annual Meeting Poster #149

Our study examines how sediment layers affect ground motion during subshear and supershear earthquake ruptures. We find that sediments can potentially cause localized supershear propagation, particularly influencing ground motion in the direction parallel to the fault. Unlike in uniform material models, when sediments are present, a larger fault-normal velocity jump compared to fault-parallel doesn't necessarily rule out shallow supershear propagation but may indicate deeper subshear propagation. Conversely, a larger fault-parallel jump suggests a supershear propagation in both sediment and bedrock (global supershear).

We find that shallow sediment layers have a complex, non-linear impact on supershear transition and ground motion. During global supershear propagation, sediments tend to amplify fault-parallel velocity pulses while minimally affecting the fault-normal component. In cases of global supershear propagation, we observed localized supersonic propagation within sediments, significantly altering surface velocity patterns and creating both dilatational and shear Mach cones.

Notably, all our sediment models showed substantial increases in vertical ground velocity. This finding could have important implications for hazard assessments, particularly for linear infrastructure and tsunami generation potential. Overall, our research highlights the critical need to incorporate heterogeneous material distributions in physical models, as they can dramatically influence earthquake source physics.

Citation
Abdelmeguid, M., Elbanna, A. E., & Rosakis, A. J. (2024, 09). Ground Motion Characteristics of Subshear and Supershear Ruptures in the Presence of Sediment Layers. Poster Presentation at 2024 SCEC Annual Meeting.

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