The Pennsylvania State University
Grant: $186,048 - National Science Foundation - Aug. 1, 2009
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Award Description: The mechanics of slip on low-angle normal faults (LANFs) is one of the most important unsolved problems in the geosciences. Theoretical and laboratory considerations imply that normal faults with dips of less than 30° should neither form nor be reactivated. Yet, these faults are documented in numerous field studies. Moreover, recent work shows that slip on low angle normal faults can be both seismic or aseismic. While many key advances have already been made in identifying conditions under which low angle normal faults operate, surprisingly little work has been done on exhumed fault rocks themselves. Here, we propose to investigate the mechanical behavior of natural fault gouges from LANFs. We will focus on the well-studied and well-exposed LANFs in the Southwestern US. The merit of the proposed work involves the importance and breadth of the questions being addressed. By illuminating the mechanical behavior of LANFs we will also contribute toward understanding the broader problem of the apparent weakness of major faults. The societal relevance of understanding slip on faults is clear. Earthquakes are one of the most important natural disasters in the US. This project will focus on the fundamental mechanics of tectonic faults. The project will encourage interactions among laboratory- and field-based geoscience communities, which tend to operate more independently than would be optimal.
Project Description: To test two basic hypotheses/questions: 1) The composition and fabric of gouge in LANFs make them sufficiently weak to explain slip on these severely misoriented structures, and 2) Frictional behavior of the fault gouge of LANFs generally results in stable sliding behavior, and thus limits the potential for seismicity on LANFs.We will study fault rocks from LANFs that formed both in the upper 5 km of the crust (Panamint Range, CA), and LANFs that formed at 5-10 km, where the crust should be at its strongest (the Chemehuevi detachment, CA). We will contribute two fundamental products: (1) comprehensive and robust datasets describing mechanical and transport properties of exhumed fault rocks from low-angle normal fault zones; and (2) Lab-based constraints on the evolution of fault strength, sliding stability, and permeability. Ultimately, integration of laboratory studies with field characterization of fault rock development will enable us to evaluate the relative roles of material properties, fabric development and fluids in modulating the behavior of low-angle normal faults.
Jobs Summary: Nothing to report currently. (Total jobs reported: 0)
Project Status: Less Than 50% Completed
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