Earthquake impact on submarine slopes: Subtle erosion versus significant strengthening

phys.org | 6/26/2019 | Staff
JimmyJoe (Posted by) Level 3
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Active margins, where an oceanic plate slides under a continental plate, may cause earthquakes and tsunamis. Further, they are known for shifting sediments from margin slopes into deep ocean trenches. Geologists now found evidence of earthquake-triggered surface sediment erosion on a submarine slope close to the area of the 2011 Tohoku-Oki earthquake.

Whereas most previous research assumed that sediment transport by earthquakes only happened by sliding of sediment packages (i.e. submarine landslides), that are several meters thick, the recently-discovered process of surficial remobilization involves the stripping of only a thin veneer of sediment over an extensive area. At first view a few missing centimeters of sediment do not look very spectacular. However, the fact that it affects a vast area has tremendous implications for all studies based on the remobilization of marine sediment by earthquakes, such as research on pre-historical earthquakes, deposition of organic carbon into the deep ocean and even the potential tsunami hazard by submarine landslides. "Surficial remobilization was hypothesized based on studies of basin deposits. However, to really understand this important process it is crucial to investigate the place where it takes place: the submarine slopes," explains Jasper Moernaut, Assistant Professor at the Department of Geology.

Researchers - Chemical - Analyses - Centimeter - Scale

The researchers combined chemical and physical analyses to detect small centimeter scale gaps in the sediment taken from a slope offshore Japan. Subsequent dating then revealed the potential of the gaps being caused by seismic shaking. "We were...
(Excerpt) Read more at: phys.org
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