Geodetic Science Snapshots - Technology

A new method to measure relative sea-level rise in low-elevation coastal zones combines global navigation satellite system (GNSS) data with measurements from rod surface-elevation table–marker horizons (RSET-MHs) and satellite altimetry. Combining these measurements shows that the sediments in coastal Louisiana are subsiding faster than previously recognized and thus relative sea level is rising at a higher rate.

A new way to measure seafloor motions with Global Positioning System (GPS) in shallow seas is tested in Tampa Bay, Florida. Observations over many months indicate seafloor motions in three dimensions can be measured. The method can be applied for offshore oil operations, lakes around volcanic edifices, shallow submarine regions near the coasts that are above active subduction zones and for other applications.

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.

High-rate GPS observations over long time periods after an earthquake were compiled to resolve weaker ground motions from large events. Analysis of long duration GPS signals for the 2011 Tohoku-Oki earthquake from the Plate Boundary Observatory (PBO) network in the contiguous western U.S. identifies multiple shear wave reflections and surface waves that traverse the globe multiple times. This analysis opens up a significant new way to understand the structure of the upper mantle using geodesy.

Global Navigation Satellite Systems (GNSS) networks have been established and enhanced to provide information and warning about large earthquakes and tsunamis. The Centro Sismológico Nacional (CSN) of the Universidad de Chile can collect information about an earthquake and potential tsunami from GNSS data within seconds and provide early warning to communities in Chile and the rest of the world.

Real-time Global Navigation Satellite System (GNSS) ground-based sites can measure displacements on the Earth’s surface. Here, the benefits of including GNSS in an earthquake early warning system are outlined and three different algorithms for integrating geodetic data into the USGS’s ShakeAlert system are identified.

The Global Positioning System (GPS) constellation can be used to detect dark matter. Sixteen years of ground-based GPS receiver observations were utilized to look for dark matter passing near Earth. Although no dark matter was detected, the results refine the properties of the universe, the accuracies of atomic clocks and future searches for dark matter.

An analysis of the 2016 Iniskin earthquake shows how GPS sites in Alaska may augment earthquake early warning. For a large magnitude earthquake that originates at a shallow depth, information from GPS can provide some warning before the shaking arrives in populated areas such as Anchorage. The geodetic data can rapidly and precisely define the earthquake properties to help with response and triggered hazards such as landslides and tsunamis.

The Mosul Dam on the Tigris River in Iraq was built on weak rock that is dissolving due to water infiltration since it was built. Satellite imagery shows the dam subsiding over 6 years. The subsidence increases the risk of dam failure, which would affect more than a million people living nearby and everyone who relies on the dam for energy and water.

If you want to know everything about the methods and data analysis centers for GPS networks in North America and the Caribbean, this is the review you should read. The review describes methods for determining position time series, velocities and other parameters from 2170 stations.

Combining geodetic and seismic observations can reduce the amount of time needed to assess the tsunami intensity generated by a large magnitude thrust fault earthquake along a subduction zone. Through retrospective analysis of four tsunamigenic large earthquakes in Japan and Chile, the tsunami potential at the local coast was estimated within less than 2 minutes.

The addition of geodetic data into the Pacific Northwest Seismic Network earthquake early warning system shows important enhancement to the warning system. Tests show the Geodetic First Approximation of Size and Time (G-FAST) could determine the characteristics of the 2001 Mw 6.8 Nisqually earthquake with sufficient robustness to warn communities at risk.

Combining geodetic and seismic measurements for the moderate 2014 Mw 6.1 Napa, California earthquake shows that rapid earthquake assessment is effective, so in a future real-time implementation, early responders will have more information to know where to concentrate their efforts to mitigate losses.

Before becoming a professor of physics at the University of Nevada Reno (UNR), Dr. Friedwardt Winterberg published a paper in 1955 that proposed a direct test to investigate one of the most important theories of modern physics: general relativity.

Geodetic imaging such as InSAR combined with GPS has provided the means to view the surface deformation caused by earthquakes at a high level of detail, but currently these images require up to several days to be created by an expert.

UNAVCO has helped collect and distribute huge amounts of GPS data throughout the world, on the order of several pedabytes, providing unprecedented access to free high-quality scientific data. The next step may be the development of a Geodesy Community Workbench, which would provide a unified framework for analyzing and interpreting GPS data, according to researchers at the University of Nevada in Reno.