The amount of continuous GPS data available both through EarthScope and from around the world is growing dramatically. Routine processing of these data is generating time-series of daily site positions and secular site velocities with incredible success. However, analysis techniques that explore the time dependence of crustal velocity are lacking. We are developing a method to characterize the four-dimensional crustal velocity field using continuous GPS in a systematic manner appropriate for routine processing. Time dependent crustal velocities can be used to study time dependent strain fields associated with viscous relaxation processes, aseismic slip events, and volcano deformation, and many other applications. Our method models crustal velocity using smooth continuous splines. The splines are fit to continuous position time series. This spline approach has several advantages 1) it does not assume a functional form for deformation a priori, 2) observations need not be regularly spaced in time, 3) it provides an easy decomposition of white noise and time-variable signal, and 4) it provides a continuous representation of time-variable site motion. Our time series model presently consists of an initial position, a secular velocity term, a time dependent velocity function, and white noise. The variability of the time dependent velocity function and the variance of the residual white noise are controlled by an empirically determined damping factor. The algorithm is highly configurable and appropriate for studies of both long-term and short-term signals. We demonstrate the technique using example time series from long-running continuous GPS stations in the western US and elsewhere.
AGU Fall Meeting Abstracts
- Pub Date:
- December 2007
- 1207 Transient deformation (6924;
- 1209 Tectonic deformation (6924);
- 1213 Earth's interior: dynamics (1507;
- 1236 Rheology of the lithosphere and mantle (7218;