Project Details
Projekt
Constraining the dynamics of the present-day Alps with 3D geodynamic inverse models.
Applicants
Professor Dr. Wolfgang Friederich; Professor Dr. Boris J.P. Kaus; Professor Dr. Thomas Meier
Subject Area
Geophysics
Term
from 2017 to 2021
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 363550341
Geophysical methods give insights in the present-day structure of the lithosphere and mantle, whereas geological methods tell us something about how this structure evolved over millions of years of deformation. Yet, if we want to understand the physics of mountain building in the Alps, and how deep processes interact with surface deformation, we also need constraints on the dynamics of the lithosphere. Whereas we can now numerically simulate such processes in 3D, the input parameters of these models remain uncertain. Moreover, it is often unclear how well geodynamic models fit geophysical constraints. We have recently developed a geodynamic inverse modelling approach in which geodynamic models of the present-day lithosphere are compared with geophysical data and the model parameters (rheology, temperature) are changed in an automatic manner to reduce the misfit between models and data. By framing this in a Bayesian Monte Carlo approach, we can determine the best-fit parameters as well as their uncertainty bounds even for nonlinear rheologies. It allows to create mechanically-consistent interpretations of mountain-belts and shows to which extend various proposed hypotheses agree with geophysical data. The disadvantage is that it is computationally expensive, and that there is not always a single best-fit model. Here, we will perform fully 3D geodynamic inversions of the Alpine region, to understand which mantle/crustal structures, thermal states, and rheologies are consistent with geophysical data of the Alps. In addition to GPS, topography and gravity anomalies, and in collaboration with 4D-MB members, we will also incorporate strain rate, seismicity, stress directions derived from focal mechanisms, 3D seismic anisotropy, cooling ages and results from new tomographic inversions in our geodynamic inverse models. This is likely to yield better-constrained inversion results. Doing this requires technical developments to compute synthetic geophysical data from our simulations, as well as improvements to increase the speed of the inversion method itself.Initially, we will use published data and existing tomographic models for our work, but new data will be incorporated through collaboration with other 4D-MB members. Our models will:- show what the dynamic consequences of subduction polarity changes are and give constraints on lithospheric rheology (RT1).- illustrate how the deep structure of the Alps is linked to crustal and surface deformation (RT2, RT3).- will give constraints on stress orientations in the crust and its link to deeper processes (RT4).We will make use of the results of the DSEBRA network (AF-A), geological studies of the Alps (AF-E) and contribute to 4D-numerical modelling of the Alps (AF-E). Moreover, the constraints we will obtain on the effective rheology of the lithosphere will be important for fully dynamic models of the Alpine collision zone on a million-year timescale.
DFG Programme
Priority Programmes
