--> Abstract: Preliminary Study of Sea-Floor Instability in Offshore Gulf of Alaska Tertiary Province, by Paul R. Carlson, Bruce F. Molnia, Terry R. Bruns; #90972 (1976).
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Abstract: Preliminary Study of Sea-Floor Instability in Offshore Gulf of Alaska Tertiary Province

Previous HitPaulTop R. Carlson, Bruce F. Molnia, Terry R. Bruns

The northeastern Gulf of Alaska is a region of active seismicity, intense storms, and rapid sediment accumulation. Therefore, instability of the sea floor is a serious hazard to development on the outer continental shelf (OCS).

High-resolution seismic profiles (18,000 km in 1974 and 1975) and sediment samples (400 collected in 1975) from the OCS indicate several areas that are susceptible to fault displacement, ground shaking, and ground failure. Evidence of faulting at or near the sea floor has been found on Tarr Bank, around Middleton and Kayak Islands, near structural highs south of Cape Yakataga, and adjacent to Pamplona Ridge. Very few of these faults appear to cut thick Holocene sediments, but many reach the surface in areas where the Holocene sediment is lacking or extremely thin.

Seaward of the Copper River prodelta and Malaspina Glacier are areas that contain disrupted bedding and irregular topography commonly associated with submarine slides or slumps. Both areas comprise more than 1,700 sq km of thick (> 150 m) Holocene sediments on slopes of about ½°. Additional areas of hummocky topography that suggest submarine sliding are present at the edge of the shelf and upper slope.

Other parts of the OCS that have thick accumulations of underconsolidated sediments (clayey silt and interbedded mud and sand; peak-vane shear strengths 0.01-0.09 kg/sq cm) and slopes steeper than 1° are potentially hazardous; they are susceptible to ground failure when large earthquakes provide rapid ground acceleration or tsunami or storm waves disrupt the sea floor.

AAPG Search and Discovery Article #90972©1976 AAPG-SEPM Annual Convention and Exhibition, New Orleans, LA