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Established baseline geodetic measurements to determine tectonic activity in the Rocky Mountains. Repeating these measurements in several years will quantify deformation for the first time.
One way of obtaining crustal deformation rates is by
comparing two sets of high-precision GPS measurements
taken at the same network of points at two
different times. The total errors in the two sets of
measurements must be small enough so that the
accumulated movement within the network during
the intervening time period can overcome the noise.
Our aims were two-fold: to acquire a new set of
measurements statewide in 2001 that are of the highest
possible precision using state of the art acquisition
and processing techniques using a previously
established set of control points: and to reprocess
data measured on these points 10 years earlier to
high enough precision to obtain an estimate of
crustal strain without requiring a future remeasurement.
The level of precision necessary to use GPS for tectonic
studies can only be obtained by extensive postprocessing
of data that were obtained using proper
field procedures, and if the GPS satellite orbits can be
post-processed to a high level of precision using a
global tracking network. This tracking network has
been in place and orbits calculated by the
International GPS Service since 1992, but as the original
measurements were done in 1991, we are trying
to devise our own strategy to improve the accuracy
of the satellite orbits. Furthermore, the 1991 data
were acquired by the National Geodetic Survey for
geodetic data definition and not tectonic studies, so
the potential accuracy of the reprocessed results is
reduced even further, adding to the challenge of
obtaining an immediate result. Given the anticipated
low rates of strain in the region, we must reduce the
present errors in the reprocessed data by two orders
of magnitude from its current levels if a meaningful
result is to be calculated.
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CIRES Research Theme
Geodynamics
Project Personnel
F. Blume, A.F. Sheehan
Funding Source(s)
CIRES Innovative Research Program
Publications
Blume, F., and A.F. Sheehan. 2003. Quantifying seismic hazard in the southern Rocky Mountains through GPS measurements of crustal deformation, in Engineering Geology in Colorado: Contributions, Trends, and Case Histories, Colorado Geological Survey Special Pub. 55, eds. D.D. Boyer, P.M. Santi, and W.P. Rogers, in press.
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