23-25 September 2013
GEOMAR East shore
Europe/Berlin timezone
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Dynamics of Submarine Landslides in an Active Margin from Analysis of Particle Size, 3D Seismic, and Logs: IODP Expedition 338, Nankai Trough, offshore Japan

Presented by Mr. Zachary MOORE on 23 Sep 2013 from 17:15 to 19:15
Type: Poster presentation
Session: Poster session
Track: Poster presentations

Content

The deposits of two submarine landslides were cored at Site C0021B in the Nankai Trough during Integrated Ocean Drilling Program (IODP) Expedition 338. Mass transport deposits (MTDs) are identified at 94-117 meters below seafloor (mbsf) and 133-176 mbsf by decreased porosity, tilted bedding, and semi-transparent seismic facies. Grain size analyses documented that sediment samples from 0-194 mbsf consist of two distinct lithologies: sediments from 0 - 155 mbsf are composed of approximately > 75% silt-sized, 15% clay-sized, and 5% sand-sized particles. Sediments between 155 - 194 mbsf have increased sand content (approximately 65% silt-sized, 15% clay-sized, and 20% sand-sized particles). The shallow MTD is composed of silt, while the deeper MTD is comprised of two zones: (1) silt from 133 - 155 mbsf and (2) sandy-silt from 155 – 176 mbsf. We are conducting a detailed 3D seismic and core-log correlation of MTDs to characterize slope geometry and deposit morphology of the failures. We use slope geometry, runout distance, and deposit morphology to address whether the slope failure was a relatively rapid-moving, low-viscosity failure or relatively slow-moving, high-viscosity failure. Preliminary results from seismic data indicate that MTDs are thick, blocky, and relatively viscous flows. However, given the high silt and sand content especially with high seismicity in the region, we would assume a landslide would have a high velocity, low viscosity behavior. One potential mechanism to explain this observation is seismic strengthening in which repeated shaking from non-failure earthquakes progressively dewater and thus strengthen the sediment and increase slope stability. Understanding the dynamics of failures is integral in evaluating slide-induced tsunami amplitude and landslide effects on subsea infrastructures

Place

Location: GEOMAR East shore
Address: Wischhofstr. 1-3 / D-24148 Kiel
Room: Lithothek

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