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Progress toward a Community Rheology Model of Southern California

Elizabeth H. Hearn, Michael E. Oskin, Wayne R. Thatcher, Greg Hirth, Whitney M. Behr, & Mark R. Legg

Published August 15, 2018, SCEC Contribution #8696, 2018 SCEC Annual Meeting Poster #152

The principal goal of the SCEC Community Rheology Model (CRM) TAG for SCEC5 is to develop a three-dimensional description of the rheology of southern California’s lithosphere. Though the CRM is intended as a resource for developing realistic and internally consistent model-based products for SCEC5, synthesizing constraints on temperature, composition and rheology from diverse fields has led to new insights and targets for continuing research. Since our 2017 workshop, which focused on developing a pilot CRM for the Mojave region, our TAG has made significant advances toward its next goal: delivering a preliminary CRM for all of southern California and adjacent regions.

The CRM comprises the Community Thermal Model (CTM), a Geologic Framework (GF), and a set of rheologies for the main GF rock types (including both low-strain rocks and shear zones). The CTM, which is also a stand-alone SCEC community model, will soon be available in draft form. It is currently being refined (1) using constraints from P/T conditions of erupted lavas and xenoliths sourced in the upper mantle, and (2) by accounting for transient thermal processes such as slab-free window effects and lower lithosphere foundering. The preliminary GF comprises 21 lithotectonic provinces, with boundaries registered to the CFM, and each represented with a 1D lithologic column. Whole-rock ductile flow laws for common GF rock types are being developed using mixing laws together with modal mineralogy, where available, such as from the exhumed crustal section of the Southern Sierra Nevada. These will be complimented by independent estimates of rheology based on seismic velocity data. Guidance on how to represent the geometry and rheology of viscous shear zones will also be a feature of the interim CRM. Efforts are underway to develop a web interface for sharing the model.

Key Words
Community Models, rheology

Hearn, E. H., Oskin, M. E., Thatcher, W. R., Hirth, G., Behr, W. M., & Legg, M. R. (2018, 08). Progress toward a Community Rheology Model of Southern California. Poster Presentation at 2018 SCEC Annual Meeting.

Related Projects & Working Groups
SCEC Community Models (CXM)