ABSTRACT


The March 27, 1964, earthquake was accompanied by over 110,000 square miles of crustal deformation which included warping, faulting, and horizontal distortion. Regional uplift and subsidence occurred mainly in two parallel zones, approximately 600 miles long and almost 250 miles wide that lie along the continental margin. From the earthquake epicenter in Northern Prince William Sound, the deformation extended eastward nearly 190 miles and southwestward more than 400 miles. It extended across the two zones from the chain of active volcanoes in the Aleutian Range and the Wrangell Mountains probably to the Aleutian Trench axis.

Uplift that averaged 6 feet over broad areas occurred mainly along the coast of the Gulf of Alaska, on the adjacent continental shelf, and probably on the continental slope. This uplift attained a maximum on land of 38 feet on Montague Island in southwestern Prince William Sound. Two faults exposed on Montague Island are northwest dipping reverse faults along which the northwest blocks were upthrown relative to sea level. To the north and northwest of the uplift zone, subsidence that centered over the Kodiak-Kjenai-Chugach Mountains averaged 2 1/2 feet with a maximum of 7 1/2 feet in the southwest coast.

Regional vertical deformation generated a score of destructive seismic sea waves in the Gulf of Alaska and at points far distant from Alaska. Warping resulted in permanent tilting of large lake basins and temporary reductions in the discharges of major rivers. The uplift and subsidence relative to the sea level caused extreme changes in the shoreline morphology and catastrophic effects on native fauna.

The primary fault was not exposed at the surface on land. Studies, when considered in conjunction with the pattern of deformation and seismic event, suggested a complex thrust fault dipping at a small angle from the vicinity of the Aleutian Trench. Movement was then accompanied by reverse faulting within the upper plate.

Fault scarp

All photos courtesy of Peter Haeussler, U.S. Geological Survey.

http://www.geolsoc.org.uk/template.cfm?name=Denali2

The belt of seismic activity and major zones of tectonic deformation associated with this earthquake, to a large extent, lie between and parallel to the Aleutian Volcanic Arc and the Aleutian Trench. Geologic data suggests that the earthquake related movements were but the most recent episodes of deformation that began in the late Pliocene time and has continued intermittently.

Table of Contents

Main

Abstract

Introduction

Time and Magnitude

Epicenter

Duration and Extent

Aftershocks

Deformation

Liquefaction

Tsunamis
References