Title: Deep seismic velocity changes as a probe of fault zone and volcano dynamics
Abstract: Temporal changes in seismic velocities are an important tool for tracking structural changes within the crust during transient deformation. While many geophysical processes span the crust, including volcanic unrest and large-magnitude earthquakes, most seismic monitoring methods rapidly lose sensitivity with depth. In this talk, I present an approach for deep seismic monitoring based on teleseismic receiver functions, which illuminate the crustal velocity structure from the bottom-up and provide sensitivity to velocity changes throughout the crust. I will describe results from two case studies. In the first case study, I show a time-series of seismic velocity changes for the 2019 Ridgecrest earthquake sequence. I will present evidence for coseismic velocity changes at ~15 km depth, near the base of the seismogenic zone, that decay over ~1 year but persist with a static offset to the present-day. Independent noise-based seismic monitoring methods instead show complete recovery within 3 months, suggesting that postseismic dynamics within and below the seismogenic zone are not well-captured by shallow seismic velocity changes. The second case study looks at seismic velocity changes throughout the complex crustal plumbing system of Mount St. Helens. In particular, I will use slow slip events on the nearby Cascadia megathrust as a periodic forcing on the volcanic system and use receiver functions to probe the velocity structure below the volcano at a range of strain conditions. This scheme enables rheological characterization of the magmatic system between eruptions.
Zoom Link: https://gatech.zoom.us/j/95963290955
Recording: Zoom Recording