Abstract

Pore pressures higher than hydrostatic correspond to localised reductions of the level of stress required to induce lateral mass movement in a slope, and therefore play a key role in preconditioning submarine landsliding. In this paper, we investigate whether multi-channel seismic reflection data can be used to infer potentially destabilising pore-pressure levels at a resolution and sensitivity useful for in-situ slope stability characterisation. We simulate the continuous deposition of sediment on consolidating slopes in two scenarios, with combinations of sedimentation rate and permeability distribution leading to disequilibrium compaction. Ultra-high-frequency (UHF; 0.2-2.5 kHz) seismic reflection data are computed for each model and a stochastic full waveform inversion (FWI) method is used to retrieve the sub-seabed properties from the computed seismograms. These are then interpreted as time-depth variations in the effective stress (σ') regime, and therefore local overpressure ratio and factor of safety, using a combination of p-wave velocity to σ' transforms. The results demonstrate that multi-channel UHF seismic data can provide valuable constraints on the physical properties distribution in the top 50 m below seabed at a sub-metric scale, and with a sensitivity useful to infer destabilising excess pore pressure levels.

Thematic collection: This article is part of the ‘Measurement and monitoring’ available at: https://www.lyellcollection.org/cc/measurement-and-monitoring

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