Lithosphere Viscosity Variations in Southern California

William E. Holt, Laurent G. Montesi, & Alireza Bahadori

Published August 15, 2018, SCEC Contribution #8736, 2018 SCEC Annual Meeting Poster #162

We combine stress estimates from geodynamic models and predictions of lithosphere rheology based on various SCEC community models to generate an integrated view of the strength of the lithosphere at regional scale. We use RHEOL to calculate the vertically-integrated strength of the lithosphere on a grid covering Southern California based on crustal thickness (Shen and Ritzwoller, 2016). Models assume either dry or wet rheologies for the lower crust and the mantle. In alternative model realizations, grain size is either fixed to 1cm or adjusted to satisfied piezometric relations (Twiss, 1977; van der Wal, 1993). The thermal structure is based on an analysis of shear wave velocity in the mantle and extrapolated into the crust. We compare these models with viscosity estimates obtained from geodynamic models constrained by lithosphere structure and topography along with mantle flow (Flesch et al., 2007; Klein et al., 2009; Ghosh and Holt, 2012). Our goal is to use discrepancies between the two models to guide refinements in the rheological model and include, for example, reduced strength shear zones. In this way, the refined view of lithospheric-scale rheology, using depth-dependent viscosity and heterogeneity, will be useful to understand the characteristics of long-term loading of faults in Southern California.

Key Words
rheology, crustal structure, stress, viscosity, dynamics

Citation
Holt, W. E., Montesi, L. G., & Bahadori, A. (2018, 08). Lithosphere Viscosity Variations in Southern California. Poster Presentation at 2018 SCEC Annual Meeting.

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