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首页> 外文期刊>Journal of Volcanology and Geothermal Research >Volcanic Tremor During Eruptions: Temporal Characteristics, Scaling And Constraints On Conduit Size And Processes
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Volcanic Tremor During Eruptions: Temporal Characteristics, Scaling And Constraints On Conduit Size And Processes

机译：火山喷发期间的震颤：时间特征，规模和对导管大小和过程的限制

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摘要

We investigated characteristics of eruption tremor observed for 24 eruptions at 18 volcanoes based on published reports. In particular, we computed reduced displacements (D_R) to normalize the data and examined tremor time histories. We observed: (a) maximum D_R is approximately proportional to the square root of the cross sectional area of the vent, however, with lower than expected slope; (b) about one half of the cases show approximately exponential increases in D_R at the beginnings of eruptions, on a scale of minutes to hours; (c) one half of the cases show a sustained maximum level of tremor; (d) more than 90% of the cases show approximately exponential decay at the ends of eruptions, also on a scale of minutes to hours; and (e) exponential increases, if they occur, are commonly associated with the first large stage of eruptions. We estimate the radii of the vents using several methods and reconcile the topographic estimates, which are systematically too large, with those obtained from D_R itself and theoretical considerations. We compare scaling of tremor D_R with that for explosions and find that explosions have large absolute pressures and scale with vent radius squared, whereas tremor consists of pressure fluctuations that have lower amplitudes than the absolute pressure of explosions, and the scaling is different. We explore several methods to determine the appropriate scaling. This characteristic helps us to distinguish the type of eruptions: explosive (Vulcanian or Strombolian) eruptions versus sustained or continuous ash (e.g. Plinian) eruptions. Average eruption discharge, estimated from the total volume of tephra and the total duration of eruption tremor, is well correlated with peak discharge calculated from cross sectional area of the vent and velocity of volcanic ejecta. These results suggest similar scaling between different eruption types and the overall usefulness of monitoring tremor for evaluating volcanic activity.
机译：根据公开的报告，我们调查了18座火山在24次喷发中观察到的爆发性震颤的特征。特别是，我们计算了减小的位移（D_R）以标准化数据并检查了震颤时间历史。我们观察到：（a）最大D_R大约与排气孔横截面积的平方根成正比，但是斜率低于预期； （b）大约一半的病例在爆发开始时D_R呈指数级增长，范围从几分钟到几小时不等； （c）一半的案件显示持续的最大震颤水平； （d）超过90％的案件在爆发结束时表现出大约指数衰减，而且分钟数至数小时不等； （e）指数增长（如果发生的话）通常与爆发的第一个大阶段有关。我们使用几种方法来估计通风口的半径，并与从D_R本身和理论考虑获得的地形估计值（系统上太大）进行协调。我们将震颤D_R的标度与爆炸的标度进行比较，发现爆炸具有较大的绝对压力，并且标度与排气半径的平方成正比，而震荡由压力波动组成，其振幅低于爆炸的绝对压力，标度不同。我们探索几种方法来确定适当的缩放比例。此特征可帮助我们区分喷发类型：爆炸性喷发（火山爆发或伏龙爆发）与持续性或连续性火山灰喷发（例如普利尼安）。从火山口的总体积和震颤的总持续时间估算出的平均喷发量与从喷口的横截面积和火山喷出速度计算出的峰值喷发量很好地相关。这些结果表明，在不同类型的火山喷发和监测震颤以评估火山活动的总体有用性之间存在相似的标度。

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