Elevated shear strength of sediments on active margins: Evidence for seismic strengthening

Earthquakes are a primary trigger of submarine landslides, yet some of the most seismically active areas on Earth show a surprisingly low frequency of submarine landslides. Here we show that within the uppermost 100 m below seafloor (mbsf) in previously unfailed sediment, active margins have elevate...

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Bibliographic Details
Published in:Geophysical research letters 2015-12, Vol.42 (23), p.10,216-10,221
Main Authors: Sawyer, Derek E., DeVore, Joshua R.
Format: Article
Language:English
Subjects:
Active margins
Compaction
Depth
Earth
Earthquakes
Energy
Landslides
Landslides & mudslides
Lithology
Low frequency
Marine
mass transport deposits
Mechanical stimuli
Ocean floor
Passive margins
Sea beds
Sediment
Sediments
Seismic activity
Seismic engineering
Seismic stability
seismic strengthening
Shear
Shear strength
Slope
Slope stability
Slopes
Strengthening
Stresses
submarine landslides
Surveying
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Summary:Earthquakes are a primary trigger of submarine landslides, yet some of the most seismically active areas on Earth show a surprisingly low frequency of submarine landslides. Here we show that within the uppermost 100 m below seafloor (mbsf) in previously unfailed sediment, active margins have elevated shear strength by a factor of 2–3 relative to the same interval on passive margins. The elevated shear strength is seen in a global survey of undrained shear strength with depth as well as a normalized analysis that accounts for lithology and stress state. The enhanced shear strength is highest within the uppermost 10 mbsf. These results indicate that large areas of modern day slopes on active margins have enhanced slope stability, which may explain the relative paucity of landslides. These findings lend support to the seismic strengthening hypothesis that the repeated exposure to earthquake energy gradually increases shear strength by shear‐induced compaction. Key Points Active margin sediments have higher undrained shear strength than passive margins The enhanced shear strength is highest within the first 10 m below seafloor The mechanism of enhanced strength may be related to earthquake energy
ISSN:0094-8276
1944-8007
DOI:10.1002/2015GL066603