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Sedimentation, sediment strength, and origin of Tuaheni landslide complex, Hikurangi margin, offshore North Island New Zealand
Vick, Travis J.
Vick, Travis J.
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2022
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Abstract
We investigate the origin of the Tuaheni Landslide Complex (TLC) by high sedimentation rates and fluid flow at deposition using core sample and log data from International Ocean Discovery Program (IODP) Expedition 372 Site U1517. Understanding how submarine landslides develop failure zones and weaken with time is important for identifying the potential for future failure that can impact infrastructure, generate tsunamis, and affect human life. In this study we construct a 1-D sedimentation-fluid flow model to simulate the pressure evolution within the sedimentary column through time. We focus on pressures in previously identified zones of weakness to investigate if overpressure (pressure over hydrostatic) was sufficiently high to cause failure. Our analysis includes comparing the overpressure to the onset of failure estimated with an infinite slope factor of safety approach. To better understand sediment properties after failure we run direct simple shear (DSS) tests on five core samples at different depths in and below the TLC. Based on our integrated modeling and experimental approach, we find that the high sedimentation rates during the deposition of the sediments at the failure zone produced enough overpressure to cause failure. Our DSS experiments constrain strain weakening and pore pressure generation within these sediments during failure. When we put this together, we define a way for a homogeneous system to fail at deposition, weaken with failure and strain, and experience creeping deformation.
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