Thermophysical Structure of the Crust Beneath the US Intermountain West from Multi-Observable Probabilistic Inversion

Monday, 14 December 2015
Poster Hall (Moscone South)
Mehdi Tork Qashqai, Macquarie University, ARC Centre of Excellence for Core to Crust Fluid Systems, Department of Earth and Planetary Sciences, Sydney, NSW, Australia, Juan Carlos Afonso, Macquarie University, GEMOC ARC National Key Centre, Sydney, NSW, Australia, Yingjie Yang, Macquarie University, ARC Centre of Excellence for Core to Crust Fluid Systems and GEMOC, Sydney, Australia and Derek Schutt, Colorado State University, Geosciences, Fort Collins, CO, United States
The evolution and present-day structure of tectonic provinces within the western portion of U.S remains the subject of much debate. Despite significant recent progress towards its geophysical characterisation and deformation styles, numerous competing hypotheses exist about the origin and focusing of deformation, evolution of topography, crustal composition, mantle contributions to high elevations, etc. For instance, in the Southern Rocky Mountains, mutually exclusive isostatic mechanisms have been proposed and the relative roles of felsic material vs partial melting/hydration of the lower crust in focusing deformation remain controversial. Here, we use a novel multi-observable inversion method (Afonso et al.,2013a;b) to gain insights into the processes that drive major tectonic deformations in these regions. To obtain a well-constrained crustal model, we jointly invert surface wave dispersion curves from ambient noise and earthquake data, geoid anomalies, gravity anomalies, receiver functions, surface heat flow and elevations. The internally-consistent use of these key constraining datasets, all with different sensitivities and linked through a thermodynamic formalism, ascribes to our method a unique sensitivity to the internal structure of the crust, and to its thermal and chemical signatures that are otherwise difficult to assess unambiguously. Additionally, the probabilistic formalism offers a natural platform from which to estimate representative model uncertainties. We find substantial local and regional variations in crustal properties among tectonic provinces, especially in the Southern Rocky Mountains. These findings provide important insights into the physical processes responsible for tectonic deformations in the Intermountain West region and can be used to test proposed evolutionary models and deformation mechanisms.


- Afonso et al.(2013a), . J.Geophys.Res.,doi:10.1002/jgrb.50124

- Afonso et al.(2013b), . J.Geophys. Res,doi:10.1002/jgrb.50123