CIRES Special Seminar: Bill Barnhart
Misbehaving Faults: Unraveling Unexpected Fault Slip Behavior with Geodetic Imaging
by Bill Barnhart - Assistant Professor of Geophysics at the University of Iowa.
Abstract: Over the past 25 years, remote sensing geodesy, particularly InSAR and optical geodesy, has transformed the Earth science community’s view of the subtle yet complex motions of the Earth’s surface. By measuring active deformation with unprecedented spatial and temporal resolution, these new data sets help to address a suite of fundamental problems in natural hazards, lithosphere deformation kinematics, the cryosphere and hydrosphere, and human-induced deformation. I will discuss recent advances and future directions in earthquake geodesy, focusing on where unexpected fault slip behavior highlights holes in our knowledge and forces us to reevaluate some of the most fundamental assumptions of faulting, such as Anderson-Byerlee fault kinematics. I will argue from geodetic, seismic, and geomorphic evidence that slip directions on the Hoshab Fault of Pakistan, host of the 2013 Mw7.7 Baluchistan earthquake, vary by up to 90° over several seismic cycles. This bimodal slip behavior allows a single fault to accommodate strain partitioning by switching between strike-slip and dip-slip motion, and it provides new incites into the manifestation of oblique crustal deformation and the process of fault reactivation. I will also discuss how I combine detailed geodetic analysis of earthquakes with the signature of past earthquakes recorded in the landscape to bridge the important observational gap that currently exists between portions of a single seismic cycle (geodesy and seismology) and multiple integrated earthquake cycles (paleoseismology and tectonic geomorphology).
Bio: I completed my bachelors of science in Geology from Washington and Lee University in Lexington, Virginia in 2008. There I completed a senior thesis characterizing the deformation fabrics in granites of the Penninic knappes of the Swiss Alps. I then completed my Ph.D. at Cornell University with Dr. Rowena Lohman in 2013. My dissertation focused on developing both new imaging and modeling techniques to constrain active fault deformation and stress interactions between earthquakes from InSAR observations and InSAR time series analysis. These techniques were applied to range of seismotectonic studies including the Christchurch, New Zealand earthquake sequence and triggered aseimic fault slip events in the Zagros Mountains or Iran. After Cornell, I was a Mendenhall post-doctoral fellow at the USGS National Earthquake Information Center in Golden, Colorado. At the NEIC, I worked to integrate geodetic observations into rapid, global earthquake response operations, work that I continue today with collaborators at the NEIC. In 2015, I began my current position as Assistant Professor of Geophysics at the University of Iowa.