EarthScope: observatories and findings
Research Review By:
Holt, William Department of Geosciences, Stony Brook University, Stony Brook, New York.
- EarthScope facility
- Plate Boundary Observatory
- San Andreas Fault Observatory at Depth
- Scientific discovery facilitated by EarthScope data
- Additional Readings
Along the western margin of North America lies a complex system of faults that accommodate the relative motions of the Pacific, North American, and Juan de Fuca plates. Sudden release of accumulated elastic strains via slip along faults produces earthquakes. Networks of EarthScope geodetic instrumentation (Fig. 1) are capturing these strains before, during, and after earthquakes. EarthScope also contains dense arrays of seismometers (Fig. 1) that record body and surface waves emitted by earthquakes around the world. The timing and shape of these seismic waveforms yield vital information about the structures that lie below the Earth's surface, much like medical computed tomography (CT) scans can show detailed structural variations within the human body. Ongoing detailed subsurface imaging, waveform analysis, fault-zone monitoring, and strain measurements through the EarthScope facility are revealing new insights about the Earth. Examples include the recent discovery of silent slip events (or slow-slip earthquakes) accompanied by seismic tremor activity along subduction-zone faults beneath parts of the United States, Canada, and other regions of the world, stunning images of three-dimensional geometry of subducted plates and foundering mantle drips, crustal stress changes preceding earthquakes, and samples of the San Andreas Fault brought up from nearly 3 km depth. These core samples and ongoing monitoring of the San Andreas Fault are providing the first-ever measurements of chemical and structural features of a major plate-bounding fault zone at seismogenic depths, providing scientists with an opportunity to obtain a better understanding of the physics of the nucleation, propagation, and arrest of earthquake-associated slip. EarthScope is funded by the National Science Foundation in partnership with NASA and the U.S. Geological Survey (USGS.). An EarthScope national office is responsible for the coordination of scientific, educational, and outreach activities. More information about EarthScope science, data, education, and outreach activities can be obtained through its office.
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