Earthscope

The EarthScope project is an undertaking funded by the National Science Foundation in partnership with the USGS and NASA to characterize the geology of North America. EarthScope is composed of three projects: USARRAY, the Plate Boundary Observatory PBO and the San Andreas Fault Observatory at Depth (SAFOD).

The instrumentation of USARRAY consists of a series of portable and permanent seismometers that are being installed over a 10 year period beginning in 2004. The goal of USARRAY is primarily to gain a better understanding of the structure and evolution of the continental crust, lithosphere, and mantle underneath North America.

The Plate Boundary Observatory PBO consists of a series of geodetic instruments: Global Positioning System (GPS) receivers and borehole strainmeters that are being installed to help understand the boundary between the North American and Pacific plates. The backbone includes a network of more than 130 GPS receivers that will cover, when completed, the western continental US, including Alaska, at a receiver spacing of 200 km and the eastern US at a receiver spacing of 500 km. A series of focused dense clusters of 775 permanent GPS receivers and 175 strainmeters are being installed along fault zones and volcanoes in western North America and Alaska. These permanent networks are supplemented by a pool of portable GPS receivers that can be deployed for temporary networks, to measure the crustal motion at a specific target or in response to a geologic event. The Plate Boundary Observatory portion of EarthScope is operated by UNAVCO, Inc, a non-profit organization that supports research applications of high-precision geodesy.

The San Andreas Fault Observatory at Depth (SAFOD) consists of drilling a hole across the active San Andreas Fault at a depth of approximately 3 km. Samples collected during drilling, as well as data from instruments installed in the hole, will help to better understand the process that control the behavior of the San Andreas Fault.

Some scientific questions that are being addressed by the EarthScope project and the PBO include [National Research Council, "Review of EarthScope Integrated Science" (Washington D.C., National Academy Press, 2001). ] :
* How does accumulated strain lead to earthquakes?
* Are there recognizable precursors to earthquakes?
* How does the evolution of the continent influence the motions that are happening today?
* What happens to geologic structures at depth?
* What influences the location of features such as faults and mountain ranges?
* Is it inherited from earlier tectonic events or related to deeper processes in the mantle?
* How is magma generated? How does it travel from the mantle to reach the surface?
* What are the precursors to a volcanic eruption?

External links

Information on EarthScope

* [http://www.earthscope.org The EarthScope web page]

References