The relationship between active deformation, stratigraphic architecture, and submarine slope failure in the Santa Barbara Channel, southern California

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Author(s): Wright, A.; Brothers, D. S.; Kluesner, J.; Dugan, B.; Johnson, S. Y.
Author Affiliation(s): Primary:
U. S. Geological Survey, Pacific Coastal and Marine Science Center Santa Cruz, Santa Cruz, CA, United States
Colorado School of Mines, Geophysics, Golden, CO, United States
Pacific Science Center, Seattle, WA, United States
Volume Title: AGU 2017 fall meeting
Source: American Geophysical Union Fall Meeting, Vol.2017; American Geophysical Union 2017 fall meeting, New Orleans, LA, Dec. 11-15, 2017. Publisher: American Geophysical Union, Washington, DC, United States
Note: In English
Summary: Multiple submarine landslides are documented along the slope of the seismically active Santa Barbara Basin and are proposed to have been capable of generating tsunamis with ≈2 - 20 m wave heights. Questions remain as to what factors preconditioned sections of the continental slope for failure and whether adjacent slopes are at risk for future failure. For example, the Gaviota landslide (0.01 - 0.02 km3) and Goleta landslide complex (3 - 4 km3) are surrounded by sections of intact slope sediment, but show signs of incipient failure, emphasizing the need for detailed hazard assessment of the region. Past studies have had to rely on legacy 2D seismic reflection datasets to analyze the regional framework geology and these data did not provide the necessary resolution to identity active faults and folds beneath the slope. Here we integrate 3D multichannel seismic (MCS) reflection volumes (acquired in 1995) as well as high-resolution 2D MCS and multibeam bathymetry datasets (acquired in 2016) to analyze the relationships between slope failure and near-surface deformation, stratigraphic architecture, and substrate fluid flow. The new high-resolution data reveal evidence for active deformation along a previously undocumented network of en echelon faults striking ≈25° counterclockwise to the dominant structural grain of the region. We observe a locally uplifted zone beneath the Gaviota slide that evidently deforms ≈90 ka sediment. Analogous patterns of deformation are identified beneath adjacent sections of intact slope, suggesting these areas may be preconditioned for failure. Thinning and onlap of fluid-saturated basin strata occurs above zones of active uplift and fault-propagation folding. We present a conceptual model for differential compaction that induces a lateral pressure gradient and updip migration of fluids, which creates a mid-slope zone of overpressure (i.e., reduced shear strength) along the axis of folding and explains the positioning of the Gaviota slide and adjacent incipient failures (tension fissures). Finally, we present preliminary results of 2D compaction and fluid flow modeling of the slope surrounding the Gaviota slide based on boundary conditions derived from the new geophysical data and nearby ODP Site 893.
Year of Publication: 2017
Research Program: ODP Ocean Drilling Program
Key Words: 07 Marine Geology and Oceanography; California; Cores; Deformation; East Pacific; Leg 146; Marine sediments; Mass movements; North Pacific; Northeast Pacific; ODP Site 893; Ocean Drilling Program; Pacific Ocean; Santa Barbara Basin; Santa Barbara Channel; Sediments; Slumping; Southern California; United States
Coordinates: N341715 N341715 W1200211 W1200212
Record ID: 2019068119
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