Applying Campaign GPS Data to Monitoring Extension in the Basin and Range of Arizona | Austin Holland, Geosciences, University of Arizona

Continuous GPS data show that Arizona is extending at a slower rate than the northern Basin and Range.  Unfortunately, the network of continuous GPS stations in Arizona lacks the spatial density and duration of operation necessary to determine where or if strain is concentrated within the broad extensional zone of the southern Basin and Range.  Knowing the distribution of strain could prove useful in identifying fault systems now accumulating strain, which in turn has important implications for seismic hazard analysis.

Semi-continuous GPS site TNSS and campaign measurement of TUC 1987 benchmark; Photograph by Jason Ninneman.

To address the shortcomings of the existing GPS data, campaign GPS data were collected at benchmarks throughout Arizona.  These benchmarks were previously observed by the National Geodetic Survey (NGS) using GPS in 1992 and more recently in 1998 through 1999.  Originally, these sites were observed by the NGS to establish survey control points, but the data are sufficient to establish contemporary strain rates.  By re-observing these benchmarks we can determine precisely how much the site has moved since previous observations.  If the motion is not the same for all the sites then strain is accumulating between these sites.

With assistance from the Arizona Geological Survey and two undergraduate students, we observed nearly 30 benchmarks in May 2009.  The benchmarks were broadly dispersed from the Four Corners to near Yuma, Arizona.  The data from this GPS campaign will be combined with that from 20 other sites previously observed; for a total of 50 geodetic sites observed in Arizona.   Data processing is underway and we hope to have new results from this work shortly.  More information can be found at the project’s homepage:

Austin Holland
Graduate Research Associate
Dept. of Geosciences, University of Arizona

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