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The Prevalence and Significance of Offset Magma Reservoirs at Arc Volcanoes
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  • Allan Lerner,
  • Daniel O'Hara,
  • Leif Karlstrom,
  • Susanna K Ebmeier,
  • Kyle R Anderson,
  • Shaul Hurwitz
Allan Lerner
University of Oregon

Corresponding Author:[email protected]

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Daniel O'Hara
University of Oregon
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Leif Karlstrom
University of Oregon
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Susanna K Ebmeier
University of Leeds
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Kyle R Anderson
U.S. Geological Survey
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Shaul Hurwitz
U.S. Geological Survey
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Abstract

Determining the spatial relations between volcanic edifices and their underlying magma storage zones is fundamental for characterizing long-term evolution and short-term unrest. We compile centroid locations of upper crustal magma reservoirs at 56 arc volcanoes inferred from seismic, magnetotelluric, and geodetic studies. We show that magma reservoirs are often horizontally offset from their associated volcanic edifices by multiple kilometers, and the degree of offset broadly scales with reservoir depth. Approximately 20% of inferred magma reservoir centroids occur outside of the overlying volcano’s mean radius. Furthermore, reservoir offset is inversely correlated with edifice size. Taking edifice volume as a proxy for long-term magmatic flux, we suggest that high flux or prolonged magmatism leads to more centralized magma storage beneath arc volcanoes by overprinting upper crustal heterogeneities that would otherwise affect magma ascent. Edifice volumes therefore reflect the spatial distribution of underlying magma storage, which could help guide monitoring strategies at volcanoes.
28 Jul 2020Published in Geophysical Research Letters volume 47 issue 14. 10.1029/2020GL087856