Shear Strength of Sediment Offshore Southern Alaska

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The Ohio State University

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The Surveyor Fan is the fourth largest submarine fan in the world and located in the Gulf of Alaska. The Surveyor Fan receives very high rates of sedimentation from the rapidly eroding St. Elias Mountains. Drilling during the Integrated Ocean Drilling Program (IODP) Expedition 341 in 2013 recovered 3240 m of sedimentary record from five sites within the Surveyor Fan. This project uses the shear strength data of the uppermost 100 meters to quantify the present-day slope stability of the fan. Shear strength is a measure of the sediment strength to withstand certain amounts of shear stress before it fails as a submarine landslide. Submarine landslides are capable of creating tsunamis. The Surveyor Fan is situated on an active seismic margin, therefore it is important to understand the risks and consequences of a submarine landslide because submarine landsliding events have happened in the recent past. Submarine landslides were generated by the magnitude-9.2 1964 Great Alaska earthquake at Valdez. The earthquake and submarine landslides created several tsunamis that ultimately killed 131 people as far away as California. This study shows a normal relationship of shear strength with depth, however the Surveyor Fan also has abnormally low values of shear strength for an active margin. This could be a major indicator that the Surveyor Fan is at high risk of slope failure.



geohazards, marine geology, submarine landslides, shear strength, Surveyor Fan