2012 IRIS Workshop

Constraining Lithospheric Geotherms through Joint Inversion of Surface Heatflow and Pn Temperatures

Derek Schutt: Colorado State University, Janine S. Buehler: University of California at San Diego, Anthony R. Lowry: Utah State University, Ken:

(a) Isotropic Pn velocities in the western U.S. obtained from USArray data. (b) Pn velocities are converted to estimated temperatures (with errors--not shown) using the approach of Faul and Jackson [2005], and estimated crustal thickness of Lowry and Perez-Gussinye [2011]. (c) Results of inversion showing estimated temperatures at 60 km depth. The Pacific Coast, Wyoming, and Colorado show evidence of non-steady state geotherms or compositional anomalies.

Full-resolution graphics file in original format: 0105.png

Using a grid search approach, we identify all conductive geotherms that satisfy Pn velocities, crustal thickness, and surface heatflow to map out lithospheric geotherms in the western U.S. An important advantage of this technique is that we do not have to assume a particular level or depth-distribution of crustal heat production -- rather we test all reasonable values. Regions in which the Pn velocities mapped to temperature and the surface heatflow do not match well indicate areas where the geotherm is not in a steady state, or where Pn velocities are not solely modulated by temperature.

Keywords: lithosphere, temperature, anelasticity

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