Hazard assessment during caldera unrest at the Campi Flegrei, Italy: a contribution from gravity–height gradients
Hazard assessment during caldera unrest at the Campi Flegrei, Italy: a contribution from gravity–height gradients
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意大利 Campi Flegrei 火山口骚乱期间的危险评估：重力-高度梯度的贡献
DOI：
10.1016/s0012-821x(03)00225-5
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发表时间：
2003
影响因子：
5.3
通讯作者：
G. Williams
中科院分区：
文献类型：
--
作者：
J. Gottsmann;G. Berrino;H. Rymer;G. Williams
只有通过充分的地球物理监测，才能对不稳定的火山口进行危害评估和风险缓解。我们在此展示了详细的长期微重力和变形调查如何通过评估 1981 年至 2001 年间地面膨胀和通货紧缩期间获得的重力-高度变化 (Δg/Δh) 梯度，为意大利 Campi Flegrei 火山口 (CFc) 的灾害评估做出贡献。此类梯度提供了一个框架，可用于评估火山喷发的可能性和类型。我们对 CFc 动荡的新分析使我们能够将重力勘测期间的“噪音”与深层岩浆过程的信号分开。这有助于识别 CFc 下方岩浆库内的动力学。我们发现，1982 年至 1984 年快速隆升期间的岩浆补充不足以引发类似于 1538 年蒙特诺沃火山喷发（CFc 内最近的火山喷发）的喷发，可能达一到两个数量级。此外，我们对自 1984 年以来持续通货紧缩时期的 Δg/Δh 梯度的解释表明，火山喷发活动并非迫在眉睫。自 1981 年以来，与较大重力变化相关的短期小幅膨胀被解释为反映了噪音，这在某种程度上可能是由于 CFc 下方浅层热液系统内的地下质量/密度变化造成的，表明没有火山喷发活动的风险。我们建议，监测不稳定火山口的 Δg/Δh 梯度至关重要，因为火山口从不稳定状态发展到必须预期火山喷发的状态。对全世界数十个不稳定的破火山口采用这种方法将为这些超级火山的活动变化或增加提供早期预警。
Hazard assessment and risk mitigation at restless calderas is only possible with adequate geophysical monitoring. We show here how detailed long-term micro-gravity and deformation surveys may contribute to hazard assessment at the Campi Flegrei caldera (CFc) in Italy by evaluating gravity–height change (Δg/Δh) gradients obtained during ground inflation and deflation between 1981 and 2001. Such gradients provide a framework from which to assess the likelihood and type of volcanic eruptions. Our new analysis of unrest at the CFc allows us to separate ‘noise’ during the gravity survey from the signal of deep-seated magmatic processes. This facilitates identification of the dynamics within the magma reservoir beneath the CFc. We found that magma replenishment during rapid uplift between 1982 and 1984 was insufficient, probably by one to two orders of magnitude, to trigger an eruption similar to the 1538 Monte Nuovo eruption, the most recent volcanic eruption within the CFc. Furthermore, our interpretation of Δg/Δh gradients for the ongoing period of deflation since 1984 suggests that eruptive volcanic activity is not imminent. Short periods of minor inflation associated with large gravity changes since 1981 are interpreted to reflect noise, which to some degree is probably due to sub-surface mass/density changes within shallow hydrothermal systems beneath the CFc, indicating no risk of eruptive volcanic activity. We propose that monitoring Δg/Δh gradients at restless calderas is essential as a caldera develops from a state of unrest to a state where volcanic eruptions have to be anticipated. Adoption of this method for the several tens of restless calderas world-wide will provide early warning of changes in or increase of activity at these supervolcanoes.