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.