Seismic-Hazard Maps for Alaska and the Aleutian Islands

This map is intended to summarize the available quantitative information about
seismic ground motion hazard in Alaska from geologic and geophysical sources.

Probabilistic seismic hazard maps were prepared for Alaska portraying peak
horizontal ground acceleration and horizontal spectral response acceleration
for 0.2, 0.3, and 1.0 second periods with probabilities of exceedance of 10% in
50 years and 2% in 50 years. This particular data set is for horizontal
spectral response acceleration for 0.3 second period with a 10% probability of
exceedance in 50 years. All of the maps were prepared by combining hazard
derived from spatially- smoothed historic seismicity with hazard from
fault-specific sources. The acceleration values contoured are the random
horizontal component. The reference site condition is firm rock, defined as
having an average shear-wave velocity of 760 m/sec in the top 30 meters
corresponding to the boundary between NEHRP site classes B and C.

This data set represents the results of calculations of hazard curves for a
grid of points with a spacing of 0.1 degrees in latitude and longitude. The
grid of points were contoured to produce the final representation of the
seismic-hazard.

A description of how the underlying geologic and geophysical data were prepared
as well as the methodology used in calculating hazard for a geographic location
can be found in the following report:

Wesson, Robert, Frankel, Arthur, Mueller, Charles, and Harmsen, Stephen, 1999,
Probabilistic Seismic Hazard Maps of Alaska: U.S. Geological Survey Open-File
Report 99-36, 48 p.