Forecasting future eruptions of Vesuvius is an important challenge for volcanologists, as its reawakening could threaten the lives of 700,000 people living near the volcano. Critical to the evaluation of hazards associated with the next eruption is the estimation of the depth of the magma reservoir, one of the main parameters controlling magma properties and eruptive style. Petrological studies have indicated that during past activity, magma chambers were at depths between 3 and 16 km (refs 3-7). Geophysical surveys have imaged some levels of seismic attenuation, the shallowest of which lies at 8-9 km depth, and these have been tentatively interpreted as levels of preferential magma accumulation. By using experimental phase equilibria, carried out on material from four main explosive events at Vesuvius, we show here that the reservoirs that fed the eruptive activity migrated from 7-8 km to 3-4 km depth between the ad 79 (Pompeii) and ad 472 (Pollena) events. If data from the Pomici di Base event 18.5 kyr ago and the 1944 Vesuvius eruption are included, the total upward migration of the reservoir amounts to 9-11 km. The change of preferential magma ponding levels in the upper crust can be attributed to differences in the volatile content and buoyancy of ascending magmas, as well as to changes in local stress field following either caldera formation or volcano spreading. Reservoir migration, and the possible influence on feeding rates, should be integrated into the parameters used for defining expected eruptive scenarios at Vesuvius.
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机译：预报维苏威火山的未来爆发是火山学家的一项重要挑战，因为维苏威火山的重新唤醒可能会威胁到靠近火山的70万人的生命。评估与下一次喷发有关的危害的关键是岩浆储层深度的估算，岩浆储层的深度是控制岩浆性质和喷发方式的主要参数之一。岩石学研究表明，在过去的活动中，岩浆室的深度在3至16 km之间（参考文献3-7）。地球物理勘测成像了一些地震衰减水平，其中最浅的地震深度为8-9 km，这些已被初步解释为优先岩浆堆积水平。通过对维苏威火山的四个主要爆炸事件的物料进行实验相平衡，我们在这里表明，提供爆发活动的储层在公元79年（庞贝城）和公元79年之间的深度从7-8 km迁移到3-4 km 472（Pollena）事件。如果包括18.5年以前的Pomici di Base事件和1944年的维苏威火山爆发的数据，则该油藏的总向上迁移量为9-11公里。上地壳优先岩浆沉积水平的变化可归因于上升岩浆的挥发性含量和浮力的差异，以及火山口形成或火山扩散后局部应力场的变化。水库的迁徙以及对进食速度的可能影响，应整合到用于定义维苏威火山预期喷发情景的参数中。
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