Exploring submarine slope failures with seismic data and physical laboratory experiments

点击翻译按钮获取中文摘要

Submarine slope failures occur on margins worldwide and can lead to damaging tsunamis both locally and on distant shores. Geophysical data (bathymetric and seismic) from passive continental margins document that these failures range from thin (less than 1 m) to thick (greater than 100 m) units, may have moved 100s of km, and can behave like a fluid or a solid. These analyses combined with numerical models of submarine slope failures suggest the failures are triggered when shallowly buried sediments are perturbed by an external stress such as a change in fluid pressure or earthquake-related shaking. Existing borehole samples and geophysical data provide a snapshot of what the materials look like after failure and numerical models provide predictions of how failures started, yet there is a lack of direct observations of the failure process which affects the final deposits. This project will characterize failure deposits offshore North Carolina using existing data from the North American Margin Community Seismic Experiment. A scaled, physical model with a novel triggering mechanism will be built to create and visualize failure dynamics. The project will advance process-based modeling techniques to incorporate how initial conditions, initiation mechanism, and failure behavior are linked. As part of the broader impacts a graduate student will be trained across multiple disciplines (seismology, sedimentology, geomechanics and engineering) as part of this project. Overall, the project will contribute to society by improving risk assessment for slope failures and tsunami generation along the US coastline. This project will integrate existing field data from the GeoPRISMS-funded Eastern North American Margin Community Seismic Experiment with laboratory and numerical models allowing for a process-based analysis of slope failures that links failure type and dynamics to initial conditions and driving mechanisms including earthquake shaking and fluid pressure changes. Laboratory experiments will provide a control on initial conditions (sediment type and properties), fluid pressures (magnitudes and distribution), and earthquake sources (location and energy) while initiating slope failures and observing failure dynamics. Numerical models will simulate the processes observed in nature and provide a means to link lab-scale experiments with field-scale observations. The project will address the following hypotheses: 1) differences between seismic velocity profiles within submarine slope failure deposits and adjacent, unfailed deposits record different effective stress and strength profiles; 2) effective stress and strength of sediments at the onset of failure impact the slope failure type and mobilization behavior of failed submarine sediments; and 3) slope failure trigger mechanism impacts slope failure dynamics and evolution, which influences their tsunami-generating potential. The overall project objective is to describe and characterize links between failure type, deposits, initial conditions, and driving mechanisms, which will increase the ability to use slope failure deposits in the sedimentary record to evaluate driving mechanisms. This will improve our ability to understand the history and distribution of slope failures and their tsunami potential. The project will also provide constraints on conditions that may produce large tsunami, which can inform risk assessment for slope failure and associated tsunami hazard.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.