How Do Fault Systems Release Strain? Insights Using Novel Geodetic Imaging Techniques

Surface deformation from large-magnitude earthquakes provides useful insight into faulting mechanics and the rupture process at depth. However, measurement of the surface deformation pattern close to fault ruptures (< 2 km) remains largely limited. For example, GPS data are commonly too sparse to capture complex surface motion, while Interferometric Synthetic Aperture Radar (InSAR) typically decorrelates in such regions due to high phase gradients, and traditional field surveys usually cannot constrain diffuse, off-fault deformation. Sub-pixel correlation of optical images taken before and after earthquakes, however, is well optimized to retrieve the full surface displacement close to the fault rupture, providing a complementary technique to standard geodetic methods. I will present optical correlation results that reveal the near-field deformation pattern of the 1992 Mw 7.3 Landers and 1999 Mw 7.1 Hector Mine earthquakes in high spatial resolution. I will demonstrate how such measurements can deepen our understanding of fault zone deformation, from how the magnitude of distributed, inelastic strain may vary between fault systems to how fault slip is distributed with depth. These results have important implications for understanding the dynamics of rupture, the hazard posed by ruptures to the urban environment, and estimates of geologic fault slip rates for our understanding of plate kinematics.

Chris graduated with his Bachelor and Masters from Imperial College of London in 2010 in Geology and Geophysics. Maintaining his interest in active tectonics, Chris went on to pursue his PhD at USC with Prof. James Dolan, studying fault-zone deformation along surface ruptures using field and geodetic techniques. Chris has now completed a one year post-doc at UC Berkeley, and is now a postdoc fellow at JPL in Pasadena, currently using GPS and InSAR to better understand faulting processes at shallow depths and postseismic processes.