Submarine Landslide Exploration through Scientific Drilling, Seismic Data, and Numerical Modeling
Abstract
Scientific ocean drilling provides unprecedented access to submarine slides, which are some of the largest sedimentary deposits on Earth and can generate tsunamis putting coastal communities at risk. We provide a snapshot of knowledge gained from IODP drilling in slide-prone regions: the Mississippi Fan, the Nankai subduction zone, the Lesser Antilles volcanic islands, and the Hikurangi margin. IODP Expedition 308 targeted a succession of slide deposits in the Mississippi Fan, northern Gulf of Mexico. Key to the evolution of this system is a sand-rich basin-floor fan rapidly buried by lower permeability silts and clays. In situ pressure measurements documented overpressure starting at 50 m below sea floor. Modeling concluded that overpressures required additional earthquake forcing to initiate failure that then evolved retrogressively. IODP Expeditions 316 and 333 provided access to sediments of the megasplay fault zone system and slides of the Nankai subduction zone. 3D seismic data combined with sediment analyses constrain three discrete episodes of fault activity and reveal how slope oversteepening, dynamic stress regimes, and fluid pressure associated with fault activity can precondition the slope for failure. This primes the system for repeat slope failures driven by individual tectonic or hydrogeologic events. IODP Expedition 340 was the first scientific drilling of volcanic island-arc slide deposits. Results show that large mass-wasting deposits around volcanic islands can comprise large volumes of seafloor sediment, which has significant implications for tsunami generation. In some cases that slope failure is an ongoing, creep-like process. IODP Expedition 372 analyzed a creeping slide along the Hikurangi margin. Data document two slide masses, and geotechnical data suggests that the base of the upper slide is extremely weak allowing for creep-like behavior and deformation. Beyond dedicated expeditions, analysis of legacy data from drilling across tectonic regimes and geologic environments has provided insights on the role that seismic activity plays in strengthening sediments and altering slope stability. Future drilling programs can address failure evolution and morphology and their feedback to tsunami potential and thus increase geohazard knowledge.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2020
- Bibcode:
- 2020AGUFMOS026..02D
- Keywords:
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- 3344 Paleoclimatology;
- ATMOSPHERIC PROCESSES;
- 0448 Geomicrobiology;
- BIOGEOSCIENCES;
- 8137 Hotspots;
- large igneous provinces;
- and flood basalt volcanism;
- TECTONOPHYSICS;
- 8155 Plate motions: general;
- TECTONOPHYSICS