Observation of Geodetic and Seismic Deformation with the Global Positioning System

Abstract

Geophysical ground motion occurs over a broad temporal spectrum, ranging from very high frequency seismic oscillations (>100 Hz) to very long period tectonic deformation at geologic time scales (millions of years). This dissertation focuses on motions that can be observed geodetically with continuous position measurements from the Global Positioning System (GPS). The work is divided into two sections: a low frequency analysis using the longest available spans of continuous GPS data (11 years), and a high frequency analysis using data with short time increments (30 s). For the low frequency analysis, GPS phase observations from archived stations were collected from Scripps Orbit and Permanent Array Center and new daily receiver coordinates, satellite orbits, and Earth Orientation Parameters were generated for the period January 20, 1991-January 12, 2002 with uniform software, measurement models, and global reference frame. From resulting position time series, a linear trend, annual and semi-annual oscillations, and offsets are simultaneously estimated. Global fiducial sites have postfit root-mean-square (rms) scatters of 2-3 mm (north), 3-5 mm (east), and 8-10 mm (up). For the Southern California Integrated GPS Network, additional model parameters include coseismic offsets and postseismic exponential decays and rate changes where appropriate. Regional stacking is used to eliminate global errors and reduce noise by a factor of 2; postfit noise rms scatter is nearly 1 mm (horizontally) and 3.5 mm (vertically). All parameters are estimated with full white noise + flicker noise covariances. The high frequency analysis is performed using a new processing technique called "instantaneous positioning", in which integer-cycle phase ambiguities are resolved every 30 s with only single epochs of dual-frequency phase and pseudorange data. Temporal stacking is used to reduce multipath noise by a factor of 2. Horizontal precision of single-epoch coordinate solutions for intermediate length baselines (tens of kilometers) is <1 cm, regardless of receiver sampling rate, making it a valuable tool for measuring ground motions at even higher frequencies. To demonstrate, instantaneous positioning is used to observe dynamic ground motions from the Mw 7.1 Hector Mine earthquake along a 200 km profile in southern California.