Towards Earthquake System Science: Constraining Basal Mantle Stress Partitioning Within the Lithosphere and Crust
Abstract
Earthquake system science entails 3D characterization of deformation related physical properties - including elastic properties, density, temperature and rheology in the ductile regime, as well as frictional properties and state on faults - and incorporating these in realistic numerical models of solid-Earth dynamics. Our work builds on recent modeling of mantle flow driven lithospheric stress loading rates in the western U.S. (Becker et al., 2015), and their relation to seismicity and geodetically-inferred deformation of the region. We use EarthScope imaging of U.S. seismic and electrical conductivity structure (USArray and PBO data) to develop 3D datasets of density, temperature, and rheological structure beneath North America. Then using the NSF-CIG community code for mantle convection, ASPECT, we develop a hierarchical set of 2D/3D instantaneous thermomechanical models of increasing complexity and realism in order to understand the relationship between lithospheric/crustal stress-rates and the present-day seismicity and geodetic deformation in the western U.S. Initial intuition building layered models investigate the partitioning of basal mantle stresses into lithospheric bending and membrane stresses for different rheologies - viscous vs. visco-plastic vs. visco-elasto-plastic. Specifically, we assess how the stress partitioning influences the spatio-temporal distribution of crustal and lithospheric strain-rate. We then investigate successively more realistic models by assimilating one or more of the above 3D datasets into the numerical models by assessing the consistency between predicted near-surface strain-rates and principal stress orientations to geodetic velocities and seismicity patterns in the Intermountain Seismic Belt. Ultimately, we aim to quantify the relative contributions of long-term (viscous/plastic) vs. short-term (elastic) deformation from the inferred heterogeneous rheological structure beneath the western U.S. to the observed overall near-surface deformation field. Our results suggest that regional geodynamic data assimilation modeling studies should move beyond the assumption of purely diffusion-creep rheology for the upper boundary layer and uppermost mantle in explaining the geologically inferred long term surface topography evolution.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.T43G0506K
- Keywords:
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- 7208 Mantle;
- SEISMOLOGYDE: 8120 Dynamics of lithosphere and mantle: general;
- TECTONOPHYSICSDE: 8125 Evolution of the Earth;
- TECTONOPHYSICSDE: 8159 Rheology: crust and lithosphere;
- TECTONOPHYSICS