The Trans Alaska Pipeline data provided by Alyeska have been revised for
the 20021023 11:27 UTC Mw 6.7 Nenana, Alaska earthquake (lat 63.626, lon
-148.016).

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 "20021023_1" to "20021023_1127".

  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