SCEC Award Number 07071 View PDF
Proposal Category Collaborative Proposal (Integration and Theory)
Proposal Title A 3-D visco-plastic model of instantaneous lithospheric deformation in southern California
Name Organization
Thorsten Becker University of Southern California Eugene Humphreys University of Oregon
Other Participants post-doc: TBA
SCEC Priorities A11, A3, A2 SCEC Groups CDM, LAD
Report Due Date N/A Date Report Submitted N/A
Project Abstract
This proposal is for work on a three-dimensional (3-D), visco-plastic model of instantaneous deformation in southern California. The main expected benets for SCEC are new insights into fault and crustal stress levels and rheology, as well as fault interactions with the lower crust (i.e. the long-term behavior). We
will integrate the effect of mantle and lithospheric density anomalies and explore which rock rheologies, fault strengths, and boundary conditions satisfy the observations. This model of the tectonic state over timescales
of several earthquake cycles addresses SCEC science objectives A3 and A11, the nature of interaction between the faulted upper crust, the ductile crust, and mantle. We aim to arrive at a seismology-based (and gravity-consistent) density structure (viz. the Transverse Ranges drip, basic crustal structure, and the deep Farallon slab anomaly) and compile auxiliary information, such as heat ow observations. These data will be incorporated into a mechanical model for hypothesis testing by matching stress and strain constraints (from GPS, geology, and anisotropy). The main new contributions are the use of, 1), diverse constraints to reduce non-uniqueness, 2), mantle-based tractions, and, 3), fully 3-D, visco-plastic rheology, as required for
quantitative tests of lithospheric behavior, e.g. with regard to vertical coupling. This overall research goal is to be achieved with a multi-year project; we describe the rst stage: the construction of a simple forward model of the present-day. At a later stage, we wish to run this forward model in a formal inverse mode and incorporate the temporal evolution of the study area over the last ~ 20 Ma.