Maps showing seismic landslide hazards in Anchorage, Alaska

By Randall W. Jibson and John A. Michael

2009

Scientific Investigations Map 3077

The devastating landslides that accompanied the great 1964 Alaska earthquake 
showed that seismically triggered landslides are one of the greatest geologic 
hazards in Anchorage, Alaska.  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 approximately 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.

This database, identified as SIM 3077, has been approved for release and publication 
by the Director of the USGS.  Although this database has been subjected to rigorous 
review and is substantially complete, the USGS reserves the right to revise the data 
pursuant to further analysis and review. 
 
Furthermore, it is released on condition that neither the USGS nor the United States 
Government may be held liable for any damages resulting from its authorized or 
unauthorized use.

Any use of trade, product, or firm names is for descriptive purposes only and does not 
imply endorsement by the U.S. Government.

Although this information product, for the most part, is in the public domain, it 
also contains copyrighted materials as noted in the text.  Permission to reproduce 
copyrighted items for other than personal use must be secured from copyright owner. 

Although these data have been processed successfully on a computer system at the U.S. 
Geological Survey, no warranty expressed or implied is made regarding the display or 
utility of the data on any other system, or for general or scientific purposes, nor 
shall the act of distribution constitute any such warranty.  The U.S. Geological 
Survey shall not be held liable for improper or incorrect use of the data described 
and/or ontained herein. 


The database can be downloaded via the web from http://pubs.usgs.gov/sim/3077/.  
ArcInfo export files and ArcGIS shapefiles may be extracted after download from 
WinZip compressed files.  Use WinZip (http://www.winzip.com/) or other programs 
to extract and decompress the files.  In addition, Adobe Portable Document Format 
(PDF) files can be downloaded for the map sheets and accompanying pamphlet, from 
which paper copies may be printed.

List of files available for download:

3077_pamphlet_508.pdf
3077_sheet1_v1-1.pdf
3077_sheet2_v1-1.pdf

3077_sheet1_dn2p50yr.met -- metadata for the grid represented on
sheet 1
3077_sheet1.zip:
    3077_sheet1_dn2p50yr.e00 -- grid showing Newmark displacement values computed 
	for earthquake shaking characterized using PGA values having 2 percent probability
	of exceedance in 50 yr for shallow landslides.

3077_sheet2_dn10p50yr.met -- metadata for the grid represented on
sheet 2 3077_sheet2.zip:
    3077_sheet1_dn2p50yr.e00 -- grid showing Newmark displacement values computed 
	for earthquake shaking characterized using PGA values having 10 percent probability
	 of exceedance in 50 yr for shallow landslides.

3077_deep_transl_ls.met -- metadata for the shapefile represented on sheets 1 and 2
3077_deep_transl_ls.zip:
    deep_transl_ls.shp -- vector shapefile representing deep, translational landslides
    deep_transl_ls.shx
    deep_transl_ls.sbn
    deep_transl_ls.sbx
    deep_transl_ls.prj
    deep_transl_ls.dbf