3D investigation of controls on slope failure in the western Santa Barbara Channel
Abstract
We use 3D multichannel seismic-reflection (MCS) data, high-resolution 2D MCS profiles, multibeam bathymetry data, and core logs from ODP site 893 to investigate the structural controls on submarine slope failure along the northwestern Santa Barbara Channel, California. The slope hosts multiple offshore hydrocarbon platforms and contains several submarine landslides as well as evidence for incipient failure. We find strong correlations between slope failure and along-strike variations in the tectonostratigraphic framework. Splay faulting within the broad uplift above the north-dipping North Channel-Pitas Point (NCPP) fault system coincides with a distinct zone of compressional uplift and onlapping patterns of steeply dipping Quaternary strata. The deformation trend and zone of onlap spatially correlate with east-west trending seafloor fissures between the headwalls of the Gaviota and Goleta landslides. Attribute analyses of 3D MCS data reveals an intricate system of shallow en echelon reverse faults that offset Plio-Pleistocene stratigraphic units. Localized zones of uplift are located between the en echelon faults, one of which underlies the Gaviota Landslide headscarp. Uplift increases to the east, producing a zone of steeply dipping strata that underlies the extent of the Goleta Landslide complex. Based on material properties in Quaternary sediments at ODP Site 893, we predict a trend in compaction and porosity reduction that drives pore fluids updip toward the zone of onlap above the NCPP trend, thus reducing sediment shear strength and promoting failure. This interplay between tectonic, sedimentary, and fluid-flow processes along the splays of the NCPP fault system has created a confluence of preconditioning factors, distinguishing the Gaviota and Goleta landslides from the surrounding slopes solely by their position above zones of localized deformation within the regional uplift. Earthquakes along the NCPP fault and in the broader region likely act as triggers for failure along the preconditioned sections of the slope. The proximity of potentially unstable sections of slope to offshore infrastructure highlights the need for further investigation of the marine geohazards in the Santa Barbara Channel.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFMOS53A..03K
- Keywords:
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- 3045 Seafloor morphology;
- geology;
- and geophysics;
- MARINE GEOLOGY AND GEOPHYSICS;
- 3070 Submarine landslides;
- MARINE GEOLOGY AND GEOPHYSICS;
- 4313 Extreme events;
- NATURAL HAZARDS;
- 7221 Paleoseismology;
- SEISMOLOGY