Hazard Curve Files for 2002 National Seismic Hazard Maps, April 2004

These files contain the hazard curves used to make the 2002 national seismic hazard maps, for a grid spacing of 0.1 degrees in latitude and longitude. The 2002 maps used a denser grid spacing of 0.05 degrees, but we are distributing the curves for a coarser grid spacing to reduce the file size. These hazard curves incorporate the revisions made in April and October 2003 (see “gridded values 2003” section of website for explanation of revisions).

The file names are:

USpgadec.haz         peak ground acceleration (PGA)

US010dec.haz         0.1 sec spectral acceleration (S.A.), 5% critical damping

US020dec.haz          0.2 sec S.A.

US030dec.haz          0.3 sec S.A.

US050dec.haz          0.5 sec S.A.

US100dec.haz          1.0 sec S.A.

US200dec.haz          2.0 sec S.A.

The third line in each file is the period in seconds, with zero indicating PGA

After the third line is the set of ground motion values used to make the hazard curves, with one value per line. These values are in units of g.

Following this set of numbers are the hazard curves, one line per site.

Each line contains the latitude and longitude of the site and the values of the annual frequency of exceedance for the hazard curve at that site. These values of the annual frequency of exceedance correspond to the ground motion values given near the top of the file, in order.

We caution about the use of the hazard curves in the western U.S. for annual frequencies of exceedance less than 1 x 10 ^{–4 style="VERTICAL-ALIGN: baseline"> .} In some areas there are very long recurrence time faults that are not included in the hazard calculation.