University of Washington: Project Overview – Our program used five temperature-salinity-turbidity instruments and 20 temperature loggers as add-on sensor packages to Ocean Bottom Seismometers (OBS) in order to further our understanding of turbidity flows on the SE Alaskan margin.  These sensor packages would be added to existing OBS deployment frames as part of the marine component of the EarthScope/GeoPRISM program for the Alaskan margin.  The recovered sensor data would be used to examine correlations betwe (...)

University of Washington: Project Overview – Our program used five temperature-salinity-turbidity instruments and 20 temperature loggers as add-on sensor packages to Ocean Bottom Seismometers (OBS) in order to further our understanding of turbidity flows on the SE Alaskan margin.  These sensor packages would be added to existing OBS deployment frames as part of the marine component of the EarthScope/GeoPRISM program for the Alaskan margin.  The recovered sensor data would be used to examine correlations between recently-triggered turbidity currents that envelop the OBS instruments and local/distant seismic events. Possible external correlations may also include storms, near-bottom water column behavior, and spontaneous slope failures as possible triggering mechanisms for sediment slope failures. Recent studies of Cascadia, Costa Rica, Sumatra and Tohoku margins have shown that sediment gravity flows on continental margins occur far more frequently than previously assumed, and these flows can have both local and distant triggering sources. The relatively high occurrence intervals of these turbidity flows, with multiple events per year detected on several globally-distributed margins, suggests the need to make these observations on the Alaskan margin as a valuable experiment-of-opportunity.

Evaluating the frequency, geographical scale, and geological environment of these gravity-driven slope failures on an active and diverse continental margin such as Alaska has major impact on our understanding of (a) the source-to-sink sediment migration component of the global carbon cycle, (2) the tsunami-genic potential of steep sediments on unstable slopes that overlie an active subduction zone, and (3) the ability to use of turbidite frequency in sediment cores as indicators of the recurrence intervals for great mega-thrust earthquakes.  Data to be interpreted in this proposal include (a) temperature, (b) salinity, (c) water column turbidity, and also (d) seismic accelerations from the OBS instruments.  Additional data required to evaluate correlations include (a) meteorological data, for example to determine the timing and intensity of storms, (b) satellite altimetry and temperature data to document upper-ocean eddies in the water column that may extend into the deep ocean, (c) earthquake seismic data from global networks and (d) from adjacent Transportable Array instruments, and (e) geodesy data from local GPS stations that can identify slow slip events.