Seismological Laboratory, Department of Earth Sciences, University College London, WC1E 6BT, London, United Kingdom.
Nat Commun. 2021 Sep 21;12(1):5555. doi: 10.1038/s41467-021-25883-y.
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 m 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.
岩浆上涌、储存和喷发是长期火山喷发和短期喷发动力学的关键。一个独特的岩浆批次如何从深部储层输送到具有可喷发岩浆的预喷发储存池仍然难以捉摸。在这里，我们表明，在阿苏火山下，重复性的超长周期信号（VLPs）之前是一个短暂的（~50-100 秒）、同步变形事件，距离 VLP 源约 3 公里。一个主要的体积分量（每个事件约 50-440 米）和一个较小的低角度正断层分量的震源机制，以及岩石学证据，表明离散的岩浆批次从超压室顶间歇性输送到靠近脆韧性过渡带的预喷发储存池。从最近的 2014 年和 2016 年喷发之前的反复变形事件中推断出的岩浆上涌速度、减压率和累积岩浆输出，与喷发方式、火山灰降落和羽流高度的回溯观测结果一致，有望实时评估即将发生的喷发。
