An Assessment of Global Positioning System Velocity Uncertainty in California

Abstract

Global Navigation Satellite System (GNSS) instruments and processing techniques provide measurements with sufficient precision to quantify subcentimeter geologic deformation (e.g., Argus et al., 2020; Dixon, 1991). The technological capabilities of GNSS spurred efforts to design a permanent network for continuous monitoring of the tectonic plate boundary in the western U.S. (Silver et al., 1998), ultimately realized by the construction of the Plate Boundary Observatory (PBO) between 2002 and 2012 that is now incorporated into the Network of the Americas (NOTA). The PBO network contains about 1,100 continuously recording global positioning system (GPS) stations and contributes most of the regional geodetic observations used by the scientific community. Daily positions and long-term velocities for these stations are freely available (Blewitt et al., 2018; Herring et al., 2016), eliminating the need for user processing of raw data and expanding data access across multiple disciplines (Jackson et al., 2007; UNAVCO, Inc., 2007). Increasing the diversity of GNSS data users justifies the existence of the NOTA and demonstrates the value of the GNSS infrastructure for scientific, government, and commercial activities (Leveson, 2009). More than a decade of daily continuous GPS observations from the PBO network have provided high-precision time series that constrain short-and long-term crustal motions in the western U.S. The dataset is

Repeating Nontectonic Seasonal Stress Changes and a Possible Triggering Mechanism of the 2019 Ridgecrest Earthquake Sequence in California

“…To correct these offsets, we follow the methodology of Johnson et al. ( 2021 ). For instance, we first model a discontinuous step with the difference between the median positions of the 14 days before and after the step, and then subtract the modeled step from the position time series.…”

“…Using metadata provided by the NGL (http://geodesy.unr.edu/NGLStationPages/steps.txt), we also find discontinuous steps pertaining to equipment changes in cGPS horizontal position time series data. To correct these offsets, we follow the methodology of Johnson et al (2021). For instance, we first model a discontinuous step with the difference between the median positions of the 14 days before and after the step, and then subtract the modeled step from the position time series.…”

Integration of DInSAR Time Series and GNSS Data for Continuous Volcanic Deformation Monitoring and Eruption Early Warning Applications

“…We used the ordinary kriging in-31 -33] supported by an exponential distribution model to construct rom the 48 GNSS station data. nown for its high precision in the horizontal directions (east and rtical motion have a larger uncertainty [34,35]. On the other hand, e range of 18.3° to 46.8°, DInSAR sensors are most sensitive to verd can help to improve ground velocity estimates in the up direction ō volcano caused widespread pressurization in the volcano, driving magma into the lower, eastern flank.…”

“…While GNSS is known for its high precision in the horizontal directions (east and north), estimates of vertical motion have a larger uncertainty [34,35]. On the other hand, with an incidence angle range of 18.3 • to 46.8 • , DInSAR sensors are most sensitive to vertical displacements and can help to improve ground velocity estimates in the up direction [20,35].…”

“…We used the ordinary kriging in--33] supported by an exponential distribution model to construct the 48 GNSS station data. wn for its high precision in the horizontal directions (east and cal motion have a larger uncertainty [34,35]. On the other hand, ange of 18.3° to 46.8°, DInSAR sensors are most sensitive to veran help to improve ground velocity estimates in the up direction Ō 4 of 33 into, and subsequent eruption from, the Puʻu ʻŌʻō crater (collotion, Figure 1) and Kilauea's lower East Rift Zone (ERZ) (Yellow den changes in lava lake levels, increased micro-seismicity around deformation along the NE strike of the ERZ were all precursory y the Hawaiian Volcano Observatory (HVO) that an impending [10,25].…”