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Scientific Investigations Map 3077

Maps Showing Seismic Landslide Hazards in Anchorage, Alaska

By Randall W. Jibson and John A. Michael

Abstract

Thumbnail of map and link to downloads directory

The devastating landslides that accompanied the great 1964 Alaska earthquake showed that seismically triggered landslides are one of the greatest geologic hazards in Anchorage. Maps quantifying seismic landslide hazards are therefore important for planning, zoning, and emergency-response preparation. The accompanying maps portray seismic landslide hazards for the following conditions: (1) deep, translational landslides, which occur only during great subduction-zone earthquakes that have return periods of ≈300–900 yr; (2) shallow landslides for a peak ground acceleration (PGA) of 0.69 g, which has a return period of 2,475 yr, or a 2 percent probability of exceedance in 50 yr; and (3) shallow landslides for a PGA of 0.43 g, which has a return period of 475 yr, or a 10 percent probability of exceedance in 50 yr. Deep, translational landslide hazard zones were delineated based on previous studies of such landslides, with some modifications based on field observations of locations of deep landslides. Shallow-landslide hazards were delineated using a Newmark-type displacement analysis for the two probabilistic ground motions modeled.

Revised November 12, 2009

First posted June 11, 2009

For additional information contact:

Science Center Chief Scientist,
USGS Geologic Hazards
Box 25046, Mail Stop 966
Denver, CO 80225
http://geohazards.cr.usgs.gov/

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Suggested citation:

Jibson, R.W., and Michael, J.A., 2009, Maps showing seismic landslide hazards in Anchorage, Alaska: U.S. Geological Survey Scientific Investigations Map 3077, scale 1:25,000, 11-p. pamphlet. [Available at URL http://pubs.usgs.gov/sim/3077]


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