Project Details
Projekt
Global relevance of gas hydrate filled fractures for slope stability
Applicant
Judith Elger, Ph.D.
Subject Area
Palaeontology
Geophysics
Geophysics
Term
from 2018 to 2021
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 408178787
Submarine landslides destroy infrastructure mounted on the seafloor and have the potential to generate devastating tsunamis, e.g. the Storegga Slide off Norway. Amongst other possible destabilization mechanisms, e.g. oversteepening or overpressure generation by elevated sedimentation rates, the dissolution of gas hydrates has been widely discussed. All over the world landslides correlate spatially with the occurrence of gas hydrates which led to the prevalent hypothesis that these slope failures are caused by the dissociation of gas hydrates at times of falling sea level or increasing bottom water temperature. Dissociation would remove the cementing hydrate from the pore space and release free gas that would provide overpressure Although this process has been shown to be realistic in numerical modelling, thirty years of research could not provide any geological or geophysical proof that it actually plays a role in submarine slope stability (. The fact that many submarine landslides are retrogressive and originated at the middle or lower continental slope suggest that other hydrated related processes favor slope failure. Nevertheless, there is no doubt that gas hydrates drastically change the geotechnical properties of the hosting sediment. Therefore, it is necessary to further study the influence of hydrates on slope stability and to test alternative hypothesis how slope stability and hydrates are linked. The overall research idea of this project is to (1) assess the global relevance of gas hydrate filled fractures for slope stability and (2) to understand the impact of shear strength variations on fault propagation and stress feature development in boreholes. Deciphering the relationship between gas hydrates and slope stability has thus far been hampered by the lack of geotechnical, geological and geophysical data from a single area in which unstable slopes are influenced by hydrates. After Leg 372 this has changed entirely. We have Logging-While-Drilling data and whole round samples from IODP Expedition 372, and 3D high-resolution seismic data that we acquired with the GEOMAR P-Cable system in 2014. For the first time, there are high-resolution 3D seismic data, high-quality sediment cores, and high-quality logging while drilling data available from one site that has demonstrably been affected by submarine slope failure. These datasets in combination with state of the art triaxial shear tests in the advanced high-pressure triaxial shear test setup at GEOMAR that allow monitoring the deformation with a 4D X-ray Micro meter-CT provide an unprecedented opportunity to make a step increase in linking gas hydrates and submarine slope stability.
DFG Programme
Infrastructure Priority Programmes
Co-Investigators
Professor Dr. Christian Berndt; Dr.-Ing. Christian Deusner; Dr. Matthias Haeckel
