SCEC Award Number 17120 View PDF
Proposal Category Collaborative Proposal (Data Gathering and Products)
Proposal Title Construction of the Geologic Framework for the Community Rheology Model
Name Organization
Michael Oskin University of California, Davis John Shaw Harvard University
Other Participants Andreas Plesch and Alex Morelan
SCEC Priorities 1a, 1c, 3b SCEC Groups CME, SDOT, Geology
Report Due Date 06/15/2018 Date Report Submitted 11/14/2018
Project Abstract
We commenced construction of a geologic framework (GF) model for southern California, based on major lithotectonic blocks. Block boundaries are defined by faults or tectonic suture zones contained within the SCEC Unified Structural Representation (USR). For this first stage of the GF, rock compositions of each block are defined as 1-D columns averaged over the block extent. A fully 3-D framework is the subject of future work. Block boundaries are drawn from faults within the SCEC USR, where intersecting the top of basement surface. For this first year, we focused on gathering lithologic information relevant to understanding the rheology of the Mojave province. This included digitizing over 1000 rock compositions from the deeply exhumed southern Sierra Nevada batholith, and compiling mineralogy and expected metamorphic transformations of underplated schist. These results were presented at the 2017 SCEC annual meeting, and form the basis for ongoing development of the GF.
Intellectual Merit Lithology is one of the primary controls on rheology. The Geologic Framework describes the profound lithologic variation across southern California at a scale appropriate for physics-based simulation of the fault system. This will better inform the physical conditions for earthquake rupture, increase understanding of the depth extent of shear zones, and constrain post-seismic deformation and stress transfer.
Broader Impacts This is an open community model that contributes to key SCEC initiatives. A U.C. Davis graduate student, Alex Morelan, was supported by this project to digitized mineralogy data. Alex will be a co-author of a short publication describing this dataset and its implications for faulting in southern California.
Exemplary Figure Figure 2. Average modal mineralogy over 5 km depth window for the Sierra Nevada batholith from point-counting of mineral phases. The composition of the batholith is remarkably uniform from 5 to 25 km depth, becoming enriched in feldspar and hornblende below 25 km. Quartz is preset as an abundant weak phase throughout.