Seasonal motions and interseismic strain measured by continuous GPS throughout the Transverse Ranges, CA

Hannah E. Krueger, Scott T. Marshall, Susan E. Owen, Gareth J. Funning, & Jack P. Loveless

Published August 11, 2016, SCEC Contribution #6626, 2016 SCEC Annual Meeting Poster #167

Tectonic continuous GPS velocity estimates are complicated by quasiperiodic motions that arise due to seasonal variations in atmospheric conditions and/or anthropogenic activity. In southern California, a dense GPS network, large seasonal motions, and seasonally variable tropospheric conditions make the region ideal for characterizing seasonal and anthropogenic motions. In this study, we utilize data from 347 permanent GPS sites in the Plate Boundary Observatory network. We calculate periods and amplitudes of seasonal motion on detrended GPS time series for each station. We find that seasonal ground motions at stations near known groundwater extraction sites, oil extraction, and other anthropogenic activity have significantly different characteristics than the surrounding stations. This suggests that identification of anomalous annual phases and/or amplitudes in GPS time series may help to identify GPS stations with signals contaminated by nontectonic sources. Based on this analysis, we identify and discard numerous contaminated sites from the data set and present an improved tectonic velocity model for southern California. Then, to isolate deformation in the Ventura and Los Angeles regions, we remove interseismic deformation associated with the San Andreas, San Jacinto, and Garlock faults using a dislocation model. The residual velocities are then inverted for strain rates highlighting zones of interseismic strain accumulation throughout the Transverse Ranges region.

Citation
Krueger, H. E., Marshall, S. T., Owen, S. E., Funning, G. J., & Loveless, J. P. (2016, 08). Seasonal motions and interseismic strain measured by continuous GPS throughout the Transverse Ranges, CA. Poster Presentation at 2016 SCEC Annual Meeting.

Related Projects & Working Groups
Tectonic Geodesy