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Professional Paper 544–B

Effects of the March 1964 Alaska Earthquake on the Hydrology of the Anchorage Area

By Roger M. Waller

Thumbnail of and link to report PDF 2.3 MB)Abstract

The Anchorage hydrologic system was greatly affected by the seismic shock. Immediate but temporary effects included increased stream discharge, seiche action on lakes, and fluctuations in ground-water levels. Generally, ground-water levels were residually lowered after the initial period of fluctuation. This lowering is attributed either to changes in the discharge zones offshore or to a change in the permeability of the aquifers by seismically induced strain.

Water supplies were disrupted temporarily by snowslides on streams and by sanding or turbidity in wells. Saltwater encroachment to wells on Fire Island seems to have increased. The approximate 3.7-foot lowering of land level and the diminished artesian head may permit further salt-water encroachment.

Increased pore pressure in the Pleistocene Bootlegger Cove Clay led to liquefaction in silt and sand lenses that contributed to the disastrous bluff landslides. Measurements after the earthquake indicate that most pore pressures are declining, whereas some remain high or are increasing.

Subsidence in the area was caused principally by tectonic readjustment, but differential compaction within the Bootlegger Cove Clay contributed to subsidences estimated to be as much as 0.6 foot beneath Anchorage.

First posted October 23, 2012
Revised August 21, 2013

For additional information:
Contact Information, Menlo Park, Calif.
   Office—Earthquake Science Center
U.S. Geological Survey
345 Middlefield Road, MS 977
Menlo Park, CA 94025
http://earthquake.usgs.gov/

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Suggested citation:

Waller, R.M., 1966, Effects of the March 1964 Alaska earthquake on the hydrology of the Anchorage area: U.S. Geological Survey Professional Paper 544–B, 18 p., 1 sheet, scale 1:61,680, https://pubs.usgs.gov/pp/0544b/.



Contents

Abstract

Introduction

Changes in the Hydrologic System

Ground Water in the Bootlegger Cove Clay

Subsidence

Conclusions

References Cited

One plate


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