Researchers: Jessica R. Murray, Benjamin A. Brooks, Emily Montgomery- Brown, Mark H. Murray, Ingrid Johanson, and Valerie Thomas, U.S. Geological Survey; Noel Bartlow, University of California, Berkeley; Yehuda Bock, University of California, San Diego; James Foster, University of Hawaii; Jeffrey Freymueller, Michigan State University; William C. Hammond, University of Nevada, Reno; Kathleen Hodgkinson, Dörte Mann, Glen S. Mattioli, David Mencin, UNAVCO; Alberto López- Venegas, University of Puerto Rico; Timothy Melbourne, Central Washington University; and Robert Smalley, University of Memphis.
Written by Linda Rowan
16 March 2020
Global Navigation Satellite Systems (GNSS) networks in the Americas provide useful observations of Earth processes and help with earthquake, volcano, tsunami and other hazard preparedness, response and mitigation. The networks consist of thousands of ground-based sites that provide high precision measurements of Earth motions and atmospheric conditions, in real time or through daily download. As receiver technology advances and more satellites are available for tracking, the GNSS observations will grow in value for research, hazard risk reduction, resource management, navigation, timing, surveying and other applications.
The United States’ Global Positioning System (GPS) was launched in 1978 and now consists of 31 satellites in orbit providing global coverage to the world for navigation and timing. Other nations and organizations have initiated satellite systems, such as Russia’s GLONASS, China’s Beidou and the European Union’s Galileo. Together these systems are known as the GNSS.
In the 1980s, geodesists began using GPS to precisely measure plate tectonic motions of millimeters per year. Early work involved taking large, heavy and expensive receivers into the field for short observational campaigns. Over time the number of receivers and research applications expanded, and the U.S. Geological Survey and the National Science Foundation led efforts to build GPS networks that could continuously measure Earth motions, crustal deformation, atmospheric conditions, water resources and much more. Today, UNAVCO with the support of the National Science Foundation operates the Network of the Americas (NOTA) with over a thousand sites in the U.S., Mexico, the Caribbean and some other regions in the Americas. The U.S. Geological Survey, universities and some state entities manage other regional networks in the U.S., focused on volcanic and seismic areas. These networks are being enhanced over time, so that many sites operate in real time for hazard risk reduction and many receivers are fully GNSS capable for more and better observations.
The authors provide an overview of the networks, partnerships and some research advances gained from years to decades of observations. The density and amount of time the networks have been observing improves the precision of the measurements, and the expansion of GNSS further enhances positioning and timing. Together, the networks and GNSS have greatly expanded our understanding of Earth processes and crustal deformation.
Regional GNSS networks have resolved aseismic fault slip, constrained earthquake slip estimates, tracked crustal deformation, enhanced our understanding of earthquake and volcano processes, and constrained the crustal deformation caused by earthquakes and other Earth processes. Real time GNSS measurements are advancing hazard mitigation by enhancing warnings about earthquakes, volcanic unrest, tsunamis and landslides. The continuous sensing of the atmosphere via GNSS allows for measurements of the electron content in the ionosphere and precipitable water vapor in the troposphere. Such real time GNSS measurements in the atmosphere can be used to forecast solar storms, severe weather, hurricane paths and wildfire potential.
Murray, J. R., N. Bartlow, Y. Bock, B. A. Brooks, J. Foster, J. Freymueller, W. C. Hammond, K. Hodgkinson, I. Johanson, A. López- Venegas, et al. (2019). Regional Global Navigation Satellite System Networks for Crustal Deformation Monitoring, Seismol. Res. Lett. 91, 552–572, doi: 10.1785/0220190113.
GNSS Network, crustal deformation, ionosphere, troposphere
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Last modified: 2020-03-30 14:27:22 America/Denver