Steady and time-dependent strain rate maps of California from inversion of GPS time series

Robert McCaffrey

Submitted August 12, 2016, SCEC Contribution #6666, 2016 SCEC Annual Meeting Poster #142

The GPS displacement time series from the Plate Boundary Observatory (PBO), Crustal Motion Model 4 (Shen et al., 2011), the Pacific Northwest (McCaffrey et al., 2013), University of Nevada Reno (UNR) and others are used to estimate time-dependent deformation of California from 1992 to the present (2016.5). The time series are initially fit by estimating the parameters of transient sources and a steady slope (site velocity). The sources include all large earthquakes since 1992 plus after-slip for many of them and several volcanic sources. The parameters are estimated by least-squares fit to the time series. (Also estimated are seasonal terms and offsets due to equipment changes and other non-tectonic causes.) Compared to other methods where earthquake offsets are estimated independently at each site and component, this approach requires the offsets to be derived from just a few source parameters and hence imposes a spatial correlation on the offsets (and therefore on the site velocities). This helps improve the estimates of velocities at sites with few observations, like campaign or short-duration continuous sites. Combined with a smoothed grid model to represent the steady motion (based on the estimated time series slopes), both the steady and time-dependent deformation can be estimated. This deformation model is used to calculate strain rates and Coulomb stress changes anywhere and at any time in the model domain. This work is funded by SCEC and supports its Community Geodetic Model effort.

McCaffrey, R. (2016, 08). Steady and time-dependent strain rate maps of California from inversion of GPS time series. Poster Presentation at 2016 SCEC Annual Meeting.

Related Projects & Working Groups
Tectonic Geodesy