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Session: Observations of Volcanism in the Three Spheres: Land, Air and Sea [Poster]

Type: Poster

Date: 4/26/2019

Time: 06:00 PM

Room: Fifth Avenue

[Withdrawn] Melt Evolution Beneath Axial Volcano Imaged Using Continuous Seafloor Compliance Data

We present the first continuous observations of the evolution of the magmatic melt system beneath Axial Volcano. We analyzed data from December 2014 through May 2018 from two cabled broadband ocean-bottom seismometers with collocated absolute pressure sensors to estimate seafloor compliance as a function of both frequency and time. The April 2015 submarine eruption induced dramatic changes in shear structure that were primarily concentrated in the lower crust (deeper than 2.5 km). We propose that the nearly 20% drop in shear velocities in the lower crust over the course of 10-12 weeks following the eruption represents the fracturing of the lower crust and the intrusion of high aspect-ratio melt sills. The subsequent rate of healing suggests that the sills were on the order of 1 meter thick. The absence of a signal on the eastern flank of the caldera indicates that the lower crustal melt pathway is relatively narrow in cross section (<1.2 km2) compared to the overlying melt chamber (≥42 km2). The lower crustal melt must also be concentrated beneath the center or to the west of the surface caldera. We find that the melt chamber and the lower crust contain minimum melt fractions of 14% and 4%, respectively, though the true melt fractions may be significantly higher. Our images demonstrate the promise of using continuous data to understand submarine volcanism and crustal accretion processes.

Presenting Author: Adrian K. Doran

Additional Authors