Vertical Deformation Dependency on Spatially Variable Elastic Plate Thickness

Lauren Ward, Bridget R. Smith-Konter, Xiaohua Xu, & David T. Sandwell

Published August 14, 2019, SCEC Contribution #9555, 2019 SCEC Annual Meeting Poster #198

Monitoring interseismic crustal deformation of the San Andreas Fault System (SAFS) through geodetic techniques provide key constraints of fault loading over a range of temporal and spatial scales. Historically, these contributions have been limited to the largely consistent record of horizontal crustal motions, yet vertical motions are now emerging as a powerful third-dimensional constraint of crustal dynamics. While vertical tectonic motions are typically attributed to normal/thrust faulting, along a transform plate boundary, contributions from elastic plate flexure (caused by bending moments applied at the ends of locked strike-slip faults) can also play an important role. To investigate strike-slip-induced vertical deformation of the SAFS plate boundary, we have developed a 4-D semi-analytic viscoelastic deformation model that simulates both the elastic and time-dependent viscoelastic response of body force dislocations embedded in an elastic plate overlying a viscoelastic half-space. A new aspect of this model is the ability to simulate lateral variations in elastic plate thickness. We use both horizontal and vertical geodetic velocities from the CGM and GNSS, along with Sentinel-1 InSAR line–of-sight velocities, and perform a joint inversion seismic moment rate to investigate the significance of spatially variable rheology on vertical deformation. We also compare modeled vertical velocities across active fault zones for a homogeneous elastic plate thickness, which in itself produces variations in vertical deformation as a function of fault locking depth and local strike with respect to the overall plate boundary. As a demonstrative case of vertical motion sensitivity to elastic plate thickness, we also utilize recent vertical geodetic observations from the M7.1 Ridgecrest earthquake.

Key Words
San Andreas Fault System, geodesy, Earthquake cycle model

Citation
Ward, L., Smith-Konter, B. R., Xu, X., & Sandwell, D. T. (2019, 08). Vertical Deformation Dependency on Spatially Variable Elastic Plate Thickness. Poster Presentation at 2019 SCEC Annual Meeting.

Related Projects & Working Groups
Stress and Deformation Over Time (SDOT)