Seismic refraction studies off the coast of Alaska: 1956-1957

Abstract

Seismic refraction profiles in the Gulf of Alaska and Bering Sea in 1956 and 1957 provide data for some tentative conclusions about sea-floor structure. The Alaskan Abyssal Plain is a wedge of sedimentary material lying over normal deep-sea floor. Deep-ocean crustal structure continues beneath the sediment to a point close to the foot of the continental slope; the possible presence of a “buried trench” at the foot of the slope needs to be checked. The eastern part of the Aleutian Trench has a greater filling of sediment than other Pacific trenches. The shelf areas near Kodiak and Unimak have thick layers of sediments over a crust that has a velocity approaching continental values; near Dixon Entrance the sediment fill is less and of extremely variable thickness. Oceanic crust is at shallow depths in Dixon Entrance and northeast of Kodiak. The Aleutian Basin differs from normal oceanic structure in having thicker sediments and a thicker “second layer” and possibly lower-than-normal mantle velocity. The Aleutian Ridge has the appearance of a volcanic mass resting atop crustal material of normal oceanic velocity but greater-than-normal thickness.