The School of Earth and Atmospheric Sciences Presents Dr. Christopher Milliner, NASA Jet Propulsion Laboratory

Using Novel Geodetic Imaging Techniques to Understand How Faults Release Strain and Track Water Storage Changes Following Extreme Hydrologic Events

Measurements of surface deformation using geodetic imaging techniques can provide observational constraints on the way faults rupture the surface and the amount of terrestrial water mass held in a region. 

Recent advancements in the resolution of optical satellite imagery, increasing density of continuous GPS networks, and near-global coverage of radar interferometry (InSAR), now offer a diverse toolset with which to study fault zone deformation and transient hydrologic processes. Here, I will first show how the use of pixel tracking applied to satellite images taken before and after two large-magnitude earthquakes can provide spatially complete measurements of the strain distribution across the fault damage zone. 

I will explore how these observations can deepen our understanding of faulting kinematics and mechanics such as, how the magnitude and width of inelastic strain may differ between fault systems, to variations of slip along ruptures and with depth.

Second, I will show how networks of continuous GPS stations can be used to track transient changes in terrestrial water storage following extreme precipitation events, such as large hurricanes. 

The mass loading effect of water on Earth’s elastic crust causes millimeter subsidence and uplift as water accumulates and dissipates, respectively, which can be measured using precise GPS elevation positioning. Using GPS measurements of elevation changes following Hurricane Harvey I will show we can infer a region’s hydrologic properties, from the amount of water a drainage area can hold, to how fast an area can dissipate water and by what means. 

The use of emerging geodetic techniques, with higher rate and more precise positioning, now allows new approaches to characterize the seismic hazard faults pose to the built environment, how faults accumulate and release strain, and improved monitoring of a region’s water security and preparation for future extreme precipitation events.