CAREER: Global Assessment of Aseismic Faulting: The Search For a Common Mechanism Among the World's Faults

University Of Oregon Eugene, Eugene OR

Investigators

Abstract

Aseismic slip, which describes fault movement that is not associated with the production of elastic waves, is a phenomenon that is not fully understood. While potential explanations, such as the presence of serpentinite or lateral variations in normal stress on the fault have been suggested, the community has been unable to explain why one active fault exhibits aseismic behavior while another only behaves seismically. One key piece of knowledge that has not been fully addressed is whether aseismic slip is prevalent among the world's faults. Aseismic slip remains largely under-reported because of the difficulty in identifying fault creep in the field without installing local instrumentation (i.e. creepmeters) or by noting the deflection of urban structures from fault movement. The PI is evaluating the prevalence of aseismic slip around the globe using Interferometric Synthetic Aperture Radar (InSAR). This technique is ideally suited to identify fault creep and other aseismic transients on a global scale in a consistent manner. The growing catalogue of synthetic aperture radar data provides global coverage of the planet allowing for a systematic assessment of major fault systems. After a global catalogue of aseismic and seismic faults is established, we perform an analysis of fault related characteristics in an effort to identify which factors are most correlated with aseismic behavior. Characteristics of interest include near-fault geology, macroscopic geometry, as well as the orientation of the regional stress field. These comparisons allow the identification or exclusion of likely mechanisms that allow faults to creep and provide insight as to why one fault exhibits aseismic slip while others do not. The collection and synthesis of several global data sets provides an ideal opportunity to involve both undergraduate and graduate students in a large research project. The modular nature of the project allows students with a wide range of technical and geological skill sets to participate. To facilitate the training of students, a series of courses are developed that cover InSAR processing and theory, GIS skills for extracting fault characteristics, and focus groups where participants perform collaborative research on a particular geographic region.