The integrated observing systems that comprise the EarthScope Facility can be used to address fundamental questions at all scales?from the active nucleation zone of earthquakes, to individual faults and volcanoes, to the deformation along the plate boundary, to the structure of the continent and planet. EarthScope data will be openly available to maximize participation from the national and international scientific community and to provide ongoing educational outreach to students and the public.
The intellectual merit of the EarthScope Facility is derived from its link to the support of fundamental research throughout the earth sciences. Through an ambitious data collection scheme and broad geographic coverage, the EarthScope Facility will provide the observational resources to encourage cross-disciplinary investigations and stimulate the next generation of research scientists. The design and implementation plan for EarthScope was developed through extensive, decade-long engagement with the scientific and educational communities. Through numerous workshops and working groups, the research community, along with federal and state partners, defined the data and tools required for geoscience to take the next step in exploring the fundamental processes that shape the structure and evolution of our continents. As the MREFC- supported construction stage for the EarthScope Facility nears completion, exciting results are already emerging from the analysis of new EarthScope data, confirming the enhanced resolution provided by this powerful new suite of observational tools.
The broader impacts of EarthScope will be achieved through an integrated education and outreach program and applications in hazard assessment, land use, and resource management. While EarthScope is a national program, it is being operated and maintained at local levels through interactions with hundreds of universities, schools, and organizations across the nation. As EarthScope collects data and makes it available, students and the public will be introduced to key unanswered scientific questions and the role that their region or discipline plays in understanding the evolution of the North American continent and the active processes driving deformation and volcanic activity. Improved understanding of the natural environment is the first step toward improved land use, environmentally sound development, and resiliency to natural hazards. With over 3,000 geographical locations, the broad distribution of EarthScope facilities will engage traditionally under-represented groups, particularly students in rural areas that have under-resourced schools and Native Americans on tribal lands (where some of the EarthScope stations will be installed). EarthScope will provide a unique opportunity for students and the public to observe geological processes in real time and to measure geological change within the time frame of an academic school year. EarthScope is providing the public with practical examples of how science advances, as they see new data being collected and watch new theories being formulated and tested.
As of September 30, 2014, UNAVCO operated and maintained 1127 GPS stations (1100 PBO core, 27 other), 75 borehole strainmeters, 79 borehole seismometers (74 strainmeters from core, 1 from a NSF Continental Dynamics project and 78 seismometers from core, 1 from a NSF Continental Dynamics project), 6 laser strainmeters (LSM) operated by the University of California, San Diego (UCSD) under a subaward from UNAVCO, 25 tiltmeters (out of 26 possible holes) and 145 meteorological stations (118 core, 27 NOAA) as part of the Plate Boundary Observatory (PBO). UNAVCO was also responsible for the management of the San Andreas Fault Observatory at Depth (SAFOD) as the SAFOD Management Office (SMO), which includes the management of a vertical laser strainmeter (VSM) in the SAFOD Main Hole and curation of all SAFOD core and cuttings. Texas A&M University (TAMU) was responsible for the management of the SAFOD core as a subaward from UNAVCO through December 31, 2013 and TAMU took over full management of the SAFOD core and related materials after October 1, 2013. UCSD was responsible for management of the VSM in the SAFOD Main Hole through April 30, 2014. UNAVCO also collects and distributes high-rate (1 Hz), low-latency (<1 s) GPS data streams (RT-GPS) from 391 stations in PBO, including 282 stations upgraded as part of the NSF-funded ARRA Cascadia initiative. Over the entire PBO O&M Phase I reporting period (2008-2014), all data types exceeded data return targets; all data types exceeded quality metric targets except for pore pressure, which remains based on the recording of M2 solid Earth tidal signal. Over the entire PBO O&M Phase I reporting period (2008-2014), PBO/SAFOD archived 48.4 TB of digital data and delivered 130.1 TB of data to the community; since PBO’s inception in 2004, 84.5 TB of data have been archived and 176.0 TB data have been delivered. In addition, more than 15,869 unique users downloaded data from PBO over the O&M Phase I period. The spatial density and temporal resolution of GPS observations, in particular from networks like the PBO have allowed us to resolve how strain varies across the plates and at plate boundaries in both in space and in time. These plate-scale measurements have been critical in constraining how the lithosphere responds to glacial loading and unloading, defining where strain occurs within the plate boundary zone interiors, the recognition of displacement and strain transients within several subduction zones [Dragert and Wang, 2011] as well as the tidal modulation of slow slip [Hawthorne and Rubin, 2010], and how plate boundary forces are accommodated within zones of diffuse deformation such as [Kreemer et al., 2012]. In addition, earthquake coseismic slip results in stress changes that can be used as energy sources for experiments that probe the rheology of the lower crust and upper mantle. In the months and years following an earthquake, nearby regions relax by viscous flow, transferring stress back to the seismogenic crust and the surface, causing post-seismic surface displacements [Pollitz et al., 2012]. These examples show how innovative applications of GPS can yield unexpected discoveries about the interactions between the solid earth and ocean. Geodetic observations are enabling us, for the first time, to follow the motion of water within Earth’s system at continental and global scales. We can now characterize changes in terrestrial groundwater storage ranging from continental-scale changes in water storage using GRACE, to regional and local changes using InSAR, GNSS for example from continuous networks like PBO, leveling, and relative gravity measurements of surface deformation accompanying aquifer-system compaction. Modeling these changes provides an understanding of the physics that drives the system and the implications of the changes on the regional aquifers. As groundwater levels continue to be drawn down to new lows, the storage capacity of the aquifer system is reduced, primarily in the fine-grained units. Quantifying the global mass flux and volume of groundwater in storage at both the local and continental scales is needed to fully characterize the water redistribution process. For example, the application of reflected GNSS signals for measuring snow depth change over time could provide a new measurement source to help understand regional snow pack [Larson et al., 2012]. In addition, the vertical displacements from the PBO network reflect in part the Earth’s elastic response to hydrological loading and these observations can be used to infer equivalent water storage [Argus et al., 2014; Borsa et al. 2014].
