Abstract
Magma ascent, storage, and discharge in the trans-crustal magmatic system are keys to long-term volcanic output and short-term eruption dynamics. How a distinct magma batch transports from a deep reservoir(s) to a pre-eruptive storage pool with eruptible magma remains elusive. Here we show that repetitive very-long-period signals (VLPs) beneath the Aso volcano are preceded by a short-lived (~50–100 s), synchronous deformation event ~3 km apart from the VLP source. Source mechanism of a major volumetric component (~50–440 m3 per event) and a minor low-angle normal-fault component, together with petrological evidence, suggests episodic transport of discrete magma batches from an over-pressured chamber roof to a pre-eruptive storage pool near the brittle-ductile transition regime. Magma ascent velocity, decompression rate, and cumulative magma output deduced from recurrent deformation events before recent 2014 and 2016 eruptions reconcile retrospective observations of the eruption style, tephra fallouts, and plume heights, promising real-time evaluation of upcoming eruptions.
Highlights
Magma ascent, storage, and discharge in the trans-crustal magmatic system are keys to longterm volcanic output and short-term eruption dynamics
More recent developments on magma transport and storage emphasize a trans-crustal magmatic plumbing system consisting of relatively long-lived crystal-rich mushes and shorter time-scale crystal-poor pools that were eventually tapped by eruptions[3,4]
The key process of distinct magma transport through these discrete chambers is not well known, even though it is intimately linked to magma ascent and discharge, controlling short-term eruption dynamics and long-term volcanic output
Summary
Storage, and discharge in the trans-crustal magmatic system are keys to longterm volcanic output and short-term eruption dynamics. Numerous petrological means have been utilized to interrogate magma ascent[7], including recent chemical diffusion-based geospeedometers[8,9] These advancements rely on retroactive analysis of eruption products, which cannot be obtained in real-time during unrest or before eruptions. Seismic resonances with periods of 0.2–200 s have been widely detected near shallow conduits or reservoirs (e.g.,
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