Geological and geophysical synthesis of the tectonics of portions of British Columbia, the Yukon Territory, and Alaska

Abstract

The seismic activity of Alaska is associated with the Aleutian Island arc and with a line of faulting in southeastern Alaska that appears to be the northward extension of the San Andreas fault system. The activity in western Alaska is enhanced where the Aleutian Range intersects the Alaska Range. It is again enhanced where the Chugach Range intersects the Aleutian Range. The Denali fault can be traced from the Bering Sea through the Kuskokwim Mountains, past Mt. McKinley, to a point past Lake Dezadeash. Here it is joined by a line of faulting associated with a northern extension of the San Andreas system. A similar line of faulting runs from Lake Clark past Anthracite Ridge to join the faulting in southeastern Alaska. It is suggested that the major Yakutat Bay earthquakes took place on a very long, straight lateral fault running from north of Yakutat Bay to south of the Queen Charlotte Islands. The Denali fault is thought to be right lateral strike slip in habit, with over 150 miles of movement. Seismic data and geologic observations indicate that the north Pacific Basin, from Baja California to the Kurile Islands at least, is and has been for a long time, rotating counterclockwise.

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