SCEC Award Number 15191 View PDF
Proposal Category Collaborative Proposal (Integration and Theory)
Proposal Title A Community Thermal Model (CTM) of the Southern California Lithosphere
Investigator(s)
Name Organization
Wayne Thatcher United States Geological Survey Colin Williams United States Geological Survey Elizabeth Hearn Consulting Geophysicist
Other Participants David Chapman
SCEC Priorities 1b, 1d, 2e SCEC Groups SDOT, CME, USR
Report Due Date 03/15/2016 Date Report Submitted 03/02/2016
Project Abstract
 We seek to develop a SCEC “Community Thermal Model” (CTM) to supply a standard reference point from which to make future refinements and corrections and provide a uniform starting point for construct- ing models that depend on temperature, thus removing the effects of differing starting assumptions. We constrain this model with observations of surface heat flow, bounds on thermal conductivity and radio- genic heat production in the crust and uppermost mantle and compute a series of 1D conductive geo- therms consistent with available data. With 2015 SCEC support we have made some preliminary calcu- lations of southern California steady-state geotherms using observational constraints on relevant control- ling parameters along the LARSE I seismic transect. The intersection of a geotherm with asthenosphere melting curves is then an estimate of lithospheric thickness and lithosphere-asthenosphere boundary (LAB) temperature Ta. These depths are in rough agreement with the seismic receiver function results of Lekic et al. (2011) that show values of 70-75 km in imaged LAB depth along the LARSE I profile. Es- timates of Ta range from 1100 to 1500 ̊C.
Intellectual Merit The thermal structure of the lithosphere is centrally important to earthquake science in general and the goals of SCEC in particular. Laboratory studies of fault slip behavior in the brittle/elastic upper crust and plastic deformation of the ductile lithosphere have shown the temperature dependence of these pro- cesses and have been widely applied to model and better understand them.
Broader Impacts Eventual application of thermo-mechanical models to better understand and quantify earthquake hazard in southern California
Exemplary Figure Fig 1: Results of preliminary calculations aimed at building at SCEC Community Thermal Model (CTM)