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首页> 外文期刊>Pure and Applied Geophysics >Three Decades of Seismic Activity at Mt. Vesuvius: 1972–2000
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Three Decades of Seismic Activity at Mt. Vesuvius: 1972–2000

机译：富士山地震活动历时三个十年维苏威火山：1972–2000年

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摘要

We analyse the seismic catalogue of the local earthquakes which occurred at Somma-Vesuvius volcano in the past three decades (1972–2000). The seismicity in this period can be described as composed of a background level, characterised by a low and rather uniform rate of energy release and by sporadic periods of increased seismic activity. Such relatively intense seismicity periods are characterised by energy rates and magnitudes progressively increasing in the critical periods. The analysis of the b value in the whole period evidences a well-defined pattern, with values of b progressively decreasing, from about 1.8 at the beginning of the considered period, to about 1.0 at present. This steady variation indicates an increasing dynamics in the volcanic system. Within this general trend it is possible to identify a substructure in the time sequence of the seismic events, formed by the alternating episodes of quiescence and activity. The analysis of the source moment tensor of the largest earthquakes shows that the processes at the seismic source are generally not consistent with simple double-couples, but that they are compatible with isotropic components, mostly indicating volumetric expansion. These components are shown to be statistically significant for most of the analysed events. Such focal mechanisms can be interpreted as the effect of explosion phenomena, possibly related to volatile exsolution from the crystallising magma. The availability of a reduced amount of high quality data necessary for the inversion of the source moment tensor, the still limited period of systematic observation of Vesuvius micro-earthquakes and, above all, the absence of eruptive events during such interval of time, cannot obviously permit the outlining of any formal premonitory signal. Nevertheless, the analysis reported in this paper indicates a progressively evolving dynamics, characterised by a generally increasing trend in the seismic activity in the volcanic system and by a significant volumetric component of recent major events, thus posing serious concern for a future evolution towards eruptive activity.
机译：我们分析了过去三十年（1972-2000年）在索马-维苏威火山中发生的局部地震的地震目录。可以将这一时期的地震活动描述为由背景水平组成，背景水平的特征在于能量释放速率较低且相当均匀，并且偶尔会出现地震活动增加的情况。这种相对强烈的地震活动期的特征在于，在临界期内能量率和震级逐渐增加。对整个时期内b值的分析证明了一个明确定义的模式，其中b值从所考虑时期开始时的约1.8逐渐降低到目前的约1.0。这种稳定的变化表明火山系统的动力不断增强。在这种总体趋势内，有可能在地震事件的时间序列中识别出由静止和活动交替发作形成的子结构。对最大地震的震源张量的分析表明，震源处的过程通常与简单的双偶不符，但与各向同性分量兼容，主要表明体积膨胀。这些成分在大多数分析事件中均具有统计学意义。这种震源机制可以解释为爆炸现象的影响，可能与结晶岩浆的挥发物释放有关。减少源矩张量所需的高质量数据量的减少，维苏威微地震的系统观测仍然有限的时期，最重要的是，在这样的时间间隔内没有爆发事件允许概述任何正式的监测信号。但是，本文报道的分析表明，动力学是逐步发展的，其特征是火山系统地震活动总体呈上升趋势，并且最近发生的重大事件的体积分量很大，因此，人们对未来爆发性活动的演变表示严重关注。 。

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