Title: Using Marine Geophysical Data to Quantify Hydration and Assess the Fate of Fluids at Subduction Zones: Observations from Recent Work and Future Perspectives
Abstract: Megathrust faults at subduction zones produce the largest earthquakes and tsunamis on Earth. The propensity for this fault rupture in the form of large earthquakes is often linked to the availability and fate of fluids sourced from subducting oceanic plates. The influence of such fluids on the effective frictional properties of the megathrust is liable to explain observations of shallow slow slip and tremors which are increasingly observed to overlap spatially with large destructive and tsunamigenic slip. Yet, established links between variations in incoming plate hydration and downdip changes in frictional properties and slip behaviors remain elusive, as do precise estimates of fluid quantities and overpressuring along the shallow megathrust. In the first part of this talk, I will discuss two major works from my Ph.D. where streamer tomography of active-source seismic data was used to quantify incoming plate water contents outboard the Alaska, Sumatra, and Mexico subduction zones. These results place important constraints on hydration mechanisms and the distributions of fluids in the outer-rise; however, limitations inherent to common seismic methods restrict our ability to discern the precise roles these fluids might play in shallow and seismogenic slip processes. Thus, for the second part of this talk I will present my current work on high-resolution velocity imaging of the shallow megathrusts and upper-plates offshore Mexico and Sumatra. I will then discuss preliminary results showing how marine electromagnetic methods, which are highly sensitive to fluids, can be used alongside seismic data to elucidate shallow megathrust hydrogeology at the geologically relevant length scales needed for robust interpretations.
Biography: I am a marine geophysicist with a bachelor’s degree in geophysics from Texas A&M University in 2017 and a Master’s degree in exploration geophysics from the Institut de Physique du Globe de Paris in 2018. I completed my Ph.D. in marine geophysics at the Lamont-Doherty Earth Observatory, Columbia University in August, 2024. I am currently a postdoctoral fellow at the University of Texas Institute for Geophysics in Austin, TX. My research interests span a range of marine contexts from mid-ocean ridges where new lithosphere is created, the abyssal plain as it evolves, and subduction trenches where it is recycled back into the Earth. My current focus is on the geophysical imaging of subduction zones to better understand the mechanisms behind different megathrust slip behaviors.
To join virtually: Zoom
Contact: acquisto@ig.utexas.edu
Website: https://www.jsg.utexas.edu/researcher/tanner_acquisto/
Recording: Zoom Recording (will be available within a week after the seminar)