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The Potential for Sediment Transport During Earthquake-Tsunami Multi-Hazards

Description: 

During strong earthquake shaking, sand beds may liquefy. Then, after strong shaking ceases, the sand beds resediment as excess pore water pressures dissipate. During ensuing tsunami attack, sediment transport occurs (onshore during runup and offshore during drawdown), and during tsunami drawdown, the sand may also re-liquefy. During the preceding process, sediment transport potential may either increase or decrease based on the size of the earthquake motion, the duration of the quiescent period, and the tsunami inundation time series. To understand the foregoing physics, we developed a model in the finite element framework OpenSees to estimate the pore water pressure response during and after earthquake shaking, and tsunami attack. We used a finite difference scheme to estimate tsunami loading along the Pacific Northwest shoreline given different rupture scenarios, and we used an earthquake motion recorded during the 2011 Great East Japan Earthquake to estimate the pore water pressure response in the sand bed during earthquake loading. The results show that the pore water pressure response during earthquake loading has a significant effect on the pore water response during the subsequent tsunami attack. Furthermore, the duration of the quiescent period, i.e., the time between the end of strong earthquake shaking and beginning of tsunami attack, has a significant impact on the pore water pressure response during tsunami loading. During the correct physical circumstances (e.g., small hydraulic conductivity, large tsunami flow height with quick drawdown velocity), the sand also liquefies during tsunami drawdown, which exacerbates sediment transport potential. To capture the significance of the results, we developed a modified Sleath parameter, to incorporate the pore water pressure response in sand beds during tsunami loading. The results and modified Sleath parameters have implications for engineers who design and retrofit coastal infrastructure, as well as paleoseismologists who retrodict the size of previous earthquakes based on observations of historic tsunami deposits.

Session: The Future of Tsunami Science, Preparedness and Response

Type: Oral

Date: 4/19/2023

Presentation Time: 04:30 PM (local time)

Presenting Author: Ben Mason

Student Presenter: No

Invited Presentation: 

Authors