Plate Boundary Observatory and related networks: GPS data analysis methods and geodetic products

Abstract

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.

GPS Vertical Land Motion Corrections to Sea‐Level Rise Estimates in the Pacific Northwest

“…Figure shows GPS vertical position time series over a 15 year window computed by PANGA (green) and, for comparison, time series for the same stations generated by the EarthScope Plate Boundary Observatory GAGE analysis centers (Herring et al, ) using the GAMIT‐only solution (PBO‐NMT product) rather than the combined GIPSY‐GAMIT solution. The GAGE GPS product (blue) is a merged position product comprising point‐positioned and double‐differenced GPS positions weighted approximately equally and only containing Cascadia stations operated by Plate Boundary Observatory (Herring et al, ). The overall structure of each time series is similar, showing nearly identical geophysical signals (e.g, amplitude of seasonal signal, net long‐term velocity).…”

A Long‐Term View of Episodic Tremor and Slip in Cascadia

“…For this study I combine separate sets of processed daily GNSS time series for monuments in the Cascadia region. The first is PBO daily position time series obtained from UNAVCO in the nam08 stable North America reference frame (Herring et al, 2016 Nevada-Reno geodesy laboratory in the NA12 stable North America reference frame, hereafter referred to as the UNR time series (Blewitt et al, 2018). I select stations between 38.95 • N and 54 • N latitude and −130 • W to −117 • W longitude, which have at least 1,460 daily observations (4 years if continuous) with no gaps exceeding 1/2 year in duration.…”

A Geodetic Strain Rate and Tectonic Velocity Model for China

“…With such an adjustment of the editing scheme, 26 more sites are included (nine sites in the Yutian earthquake affected area and 17 in the Nepal earthquake). (5) The radius of influence of an earthquake is approximated using the empirical formula (Herring, Melbourne, et al, ), where M is the magnitude of the earthquake as reported by the U.S. Geological Survey National Earthquake Information Center. All stations within d km of the epicenter are then edited with the aforementioned processing strategies and rechecked visually.…”