Contributions of Ductile Shear Zones to Postseismic Deformation: Mechanical Advances and Data Assimilation

Woods Hole Oceanographic Institution, Woods Hole MA

Investigators

Abstract

The rapid aseismic deformation that often follows earthquakes provides a natural opportunity to learn about the mechanical behavior of the Earth's crust. Geodetic data sets documenting postseismic deformation have become much more plentiful and detailed in the last few years, yet many studies of these data sets have been limited to documenting that a particular mechanism "is consistent with" the observed data. The wide variety of candidate mechanisms that have been proposed as the responsible process testifies to the importance of postseismic deformation in geodynamics, but also to our current lack of understanding of this phenomenon. The proposed study will combine a modeling framework that can simultaneously consider multiple rheological behaviors with the geodetic observations through a data assimilation algorithm. This approach, will identify the range of processes consistent with the data and rule out others, constraining the rheology of the crust directly from geodetic data. Models of shear zone formation and evolution coupled with a seismogenic fault will be developed to address whether the source of postseismic deformation is distributed or localized. The proposed study will contribute to basic knowledge of dynamical processes in the Earth's crust and to our ability to evaluate their contribution to earthquake hazards. The improved understanding of shear zone formation will have implications for structural geology and mechanical engineering, where localization is a permanent concern. The data assimilation aspect of this work will help introduce a widely successful scientific approach to fault mechanics problems. The project represents the merging of the complementary research fields of the investigators, geodynamics for one, and geodesy and data assimilation for the other. --