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Monitoring evolution of Pacific-North America plate boundary through GPS observations in Joshua Tree National Park
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INTRODUCTION
The San Andreas Fault (SAF) is not the only zone along the Pacific-North American plate boundary that accommodates movement between the two plates. In the 1990's geologists studied a series of earthquakes that occurred in the Mojave Desert, San Bernardino Mountains, and Little San Bernardino Mountains that suggested that strain is transferred from the San Andreas Fault near the Salton Trough northward to the Eastern California Shear Zone (ECSZ), which extends up through Owens Valley on the eastern side of the Sierra Nevada Mountain range. The geoscientific community does not yet fully understand the mechanism of this transfer or rates of strain that are accommodated by the ECSZ. Joshua Tree National Park (JTNP) is a part of this shear zone, therefore our understanding of the plate boundary as a whole depends on geophysical and geologic studies conducted within the park. One method used to study the distribution and rate of strain along faults is the Global Positioning System (GPS). In many cases it is more useful than standard geologic or seismic methods because it can detect strains that occur aseismically or strain along unmapped faults, or deep strain that does not break the surface. GPS measurements from within the park over the next five to ten years could be particularly useful because the data obtained from them can be integrated with data from the Plate Boundary Observatory (PBO), a National Science Foundation GPS project that consists of many hundreds of sites across the western U.S. This wealth of data will allow scientists from numerous institutions to develop move unified theories about the evolution of the Pacific-North American plate boundary. We hope to use these data to investigate several questions about the tectonics of the SAF and the ECSZ: 1) What is the distribution and rate of horizontal crustal movements within western JTNP , and therefore the path of strain through the ECSZ? 2) Is aseismic creep and/or triggered slip a significant mode of strain within the ECSZ? 3) Is there significant uplift within JTNP and how does this relate to uplift further west associated with the SAF? |
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Overview (multi-page) The monuments (photos) Photo Gallery
LINKS: Plate Boundary Observatory | UNAVCO | Earthscope | Geosciences Department | University of Arizona
Last modified: 9/28/2005 by Megan Anderson (anderson@geo.arizona.edu)