The Trans Alaska Pipeline data provided by Alyeska have been revised for
the 20021103 22:12 UTC Mw 7.9 Denali, Alaska earthquake (lat 63.517, lon
-147.525).

Important note to users of these data (posted 05/22/2003:
The information in the headers of these files is revised from that in the
headers of the files originally served by the USGS.  Changes include:

1) Revised information about the nominal filter characteristics, as
determined from an analysis of a circuit diagram for the filter.  Note in
particular that the highpass corner is at 0.1 Hz, not 0.01 Hz as was
indicated in the files originally provided by Alyeska, and that the
highpass and lowpass filters each have 2 poles rather than 1.  Details of
the nominal filter characteristics are provided in the headers.

Due to uncertainties in the instrument response, only uncorrected
acceleration time series data are currently being served.  Results from
bench tests using components similar to those deployed in the field show
deviations from nominal characteristics that could produce variations of up
to 20% in displacements determined by double integration of the
acceleration time series. The USGS is working with Alyeska to determine
more accurate calibrations, and any new information will be released as
soon as it is available.

2)        The make and model of the digitizer, along with estimates of the
digitizing accuracy and precision are included.

3)        Additional information about the baseline correction applied to
the data.

The folders (directories) and filenames for this earthquake have been
changed from "20021103_1" to "20021103_2212".

Regards,

Kent Fogleman
____________________________________________________
Kent A. Fogleman
U.S. Geological Survey
National Strong-Motion Data Center
345 Middlefield Rd., MS 977
Menlo Park, CA 94025

office: 650-329-4745
e-mail: fogleman@usgs.gov
web:    http://nsmp.wr.usgs.gov