The July 2019 Ridgecrest sequence was observed in exquisite detail by the National Science Foundation ?s (NSF) Geodetic Facility for the Advancement of Geoscience (GAGE) Network of the Americas (NOTA), which has a dense array of continuously observing Global Navigation Satellite System (GNSS) stations and subarrays of strain and seismic borehole networks in southern California. Two hundred and eighteen GNSS and 10 borehole NOTA stations within 250 km of the epicentral area recorded the sequence. Special downloads of high-rate data from sites within a specified radius of each earthquake were initiated by the GAGE Facility for the time period of 1.5 days before and 1.5 days after each event to ensure transient deformation was captured at a high-temporal resolution. Rapid field deployments of temporary GNSS stations were carried out by UNAVCO in support of NSF-funded investigators and U.S. Geological Survey activities. The data recorded by the permanent network are available from the GAGE Facility's Data Center at UNAVCO, data recorded at the temporary campaign sites will also be made available on completion of data collection. The OpenTopography project, of which UNAVCO is a partner, released a preliminary pre-event digital surface model of the area covering the Ridgecrest earth- quake sequence to support the ongoing imaging efforts to measure the deformation from these events. In this article, we document the significant amount of detailed, open-access geodetic data available from GAGE to study this sequence and advance our understanding of earthquake processes, the geodynamics of the California eastern shear zone, and our capacity to respond to damaging earthquakes for research.

The Geodesy Advancing Geosciences and EarthScope (GAGE) Facility, operated by UNAVCO, provides a diverse suite of geodetic data, derived products and cyberinfrastructure services to support community Earth science research and education. GPS data and products including decadal station position time series and velocities are provided for 2000+ continuous GPS stations from the Plate Boundary Observatory (PBO) and other networks distributed throughout the high Arctic, North America, and Caribbean regions. The position time series contain a multitude of signals in addition to the secular motions, including coseismic and postseismic displacements, interseismic strain accumulation, and transient signals associated with hydrologic and other processes. We present our latest velocity field solutions, new time series offset estimate products, and new time series examples associated with various phenomena …

The Geodesy Advancing Geosciences and EarthScope (GAGE) Facility Global Positioning System (GPS) Data Analysis Centers produce position time series, velocities, and other parameters for approximately 2000 continuously operating GPS receivers spanning a quadrant of Earth's surface encompassing the high Arctic, North America, and Caribbean. The purpose of this review is to document the methodology for generating station positions and their evolution over time and to describe the requisite trade-offs involved with combination of results. GAGE GPS analysis involves formal merging within a Kalman filter of two independent, loosely constrained solutions: one is based on precise point positioning produced with the GIPSY/OASIS software at Central Washington University and the other is a network solution based on phase and range double-differencing produced with the GAMIT software at New Mexico Institute of Mining and Technology. The primary products generated are the position time series that show motions relative to a North America reference frame and secular motions of the stations represented in the velocity field. The position time series themselves contain a multitude of signals in addition to the secular motions. Coseismic and postseismic signals, seasonal signals from hydrology, and transient events, some understood and others not yet fully explained, are all evident in the time series and ready for further analysis and interpretation. We explore the impact of analysis assumptions on the reference frame realization and on the final solutions, and we compare within the GAGE solutions and with others.

New GPS measurements demonstrate tectonic segmentation of the South Shetland Islands platform, regarded as a microplate separating the Antarctic Peninsula from the oceanic portion of the Antarctic plate. King George, Greenwich, and Livingston islands on the central and largest segment are separating from the Antarctic Peninsula at 7–9 mm/a, moving NNW, roughly perpendicular to the continental margin. Smith and Low islands on the small southwestern segment are moving in the same direction, but at 2.2–3.0 mm/a. The Elephant Island subgroup in the northeast moves at ∼7 mm/a relative to the Peninsula, like the central group, but toward the WNW. This implies that it is presently coupled to the Scotia plate on the northern side of the South Scotia Ridge transform boundary; thus the uplift of these northeasternmost islands may be caused by Scotia‐Antarctic plate convergence rather than by subduction of thickened oceanic crust.

When kinematic GPS processing software is used to estimate the trajectory of an aircraft, unless the delays imposed on the GPS signals by the atmosphere are either estimated or calibrated via external observations, then vertical height errors of decimeters can occur. This problem is clearly manifested when the aircraft is positioned against multiple base stations in areas of pronounced topography because the aircraft height solutions obtained using different base stations will tend to be mutually offset, or biased, in proportion to the elevation differences between the base stations. When performing kinematic surveys in areas with significant topography it should be standard procedure to use multiple base stations, and to separate them vertically to the maximum extent possible, since it will then be much easier to detect mis‐modeling of the atmosphere.