Plate Motions and Stresses from Global Dynamic Models

Abstract

Delineating the driving forces behind plate motions is important for understanding the processes that have shaped Earth throughout its history. However, the accurate prediction of plate motions, boundary-zone deformation, rigidity, and stresses remains a difficult frontier in numerical modeling. We present a global dynamic model that produces a good fit to such parameters by accounting for lateral viscosity variations in the top 200 kilometers of Earth, together with forces associated with topography and lithosphere structure, as well as coupling with mantle flow. The relative importance of shallow structure versus deeper mantle flow varies over Earth's surface. Our model reveals where mantle flow contributes toward driving or resisting plate motions. Furthermore, subducted slabs need not act as strong stress guides to satisfy global observations of plate motions and stress.

Effects of upper mantle heterogeneities on lithospheric stress field and dynamic topography

“…To derive our stress model we have combined CRUST 1.0 with the thickness and thermal structure of the lithosphere estimated by Artemieva (2006) in continents, and a half-space cooling model of the ocean floor with age . This is an improvement compared to much simpler representations of the upper mantle structure in previous studies using a thin-sheet/shell approximation (Steinberger et al, 2001;Lithgow-Bertelloni and Guynn, 2004;Ghosh and Holt, 2012;Ghosh et al, 2013;Wang et al, 2015). We also account for the presence of slab locations and their corresponding 15 impact on the upper mantle temperature based on Steinberger (2000).…”

“…This first-order stress pattern (long wavelength) is dynamically supported, as the controlling forces correlate well with the forces driving the plate motion in most continental areas such as North and South Americas and Europe (Solomon et al, 1980;Richardson, 1992;Zoback, 1992). Ghosh and Holt (2012) and Steinberger et al (2001) used different approaches to show that the contribution of the crust (shallow density structures) to the overall lithospheric stress pattern is rather small compared to that of the mantle A number of studies (Čadek and Fleitout, 2003;Forte and Mitrovica, 2001;Garcia-Castellanos and Cloetingh, 2011;Ghosh and Holt, 2012;Steinberger et al, 2001) have presented numerical simulations of different geophysical processes and compared their model results with observations of the lithosphere stress field, dynamic geoid, plate motion velocity and dynamic topography to better understand what processes control these surface observables. For instance, the modeled dynamic geoid typically gives a good correlation with observations, due to a large contribution of the lower mantle (Čadek and Fleitout, 2003;5 Hager et al, 1985;Richards and Hager, 1984), but is sensitive to the choice of the mantle viscosity (Thoraval and Richards, 1997).…”

“…On the one hand, Bird et al (2008) have estimated the lithospheric stress from a model that disregards the mantle flow contribution and used the fit to the observed plate velocities as a sole criterion. On the other hand, Ghosh et al (2013), Ghosh and Holt (2012), Lithgow-Bertelloni and Guynn (2004), Steinberger et al (2001) and Wang et al (2015) have aimed at assessing the influence of the mantle flow on the lithospheric stress field and have shown that the bulk mantle flow explains a large part (about 80-90 %) of the stress field accumulated in the lithosphere (Steinberger 30 et al, 2001), in both magnitude and the most compressive horizontal direction. The aim of the present study is to evaluate the contribution of the upper mantle above the transition zone to the observed spatial stress regimes of the lithosphere, while testing different approaches and data sets used to describe the thermal and rheological structure of the upper mantle.…”

Driving forces of plate motion and continental drift: Revisited

“…, Condie, 2011Condie, , 1989, 2001;Ghosh and Holt, 2012 (Uyeda, 1989). (c) The relative magnitude of each force estimated by torque balance (data from Forsyth and Uyeda, 1975).…”

Advancing geodesy in the U.S. Midcontinent: workshop report

“…CORS and PBO sites will give insight into the quality of CORS data. As the GIA studies show, using careful quality control to reject poor data yields high quality velocity fields from the CORS data.The velocity field, together with earthquake, geological, and geomorphological data (for example, Pazzaglia and others, 2010) would be analyzed using a new generation of tectonic models (for example, Ghosh and Holt, 2012) to constrain the dynamics of short-and long-term local and regional deformation processes. The practicality of doing so is shown by the fact that the GPS velocities are already being used to improve models of mantle viscosity (Peltier and Drummond, 2008), which controls the response to ice loads.…”