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An analysis of the issuance of volcanic alert levels during volcanic crises

机译:火山危机期间火山警报等级的发布分析

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Volcano Alert Levels (VALs) are used by volcanologists to quickly and simply inform local populations and government authorities of the level of volcanic unrest and eruption likelihood. Most VALs do not explicitly forecast volcanic activity but, in many instances they play an important role in informing decisions: defining exclusion zones and issuing evacuation alerts. We have performed an analysis on VALs (194 eruptions, 60 volcanoes) to assess how well they reflect unrest before eruption and what other variables might control them. We have also looked at VALs in cases where there was an increase in alert level but no eruption, these we term 'Unrest without eruption' (UwE). We have analyzed our results in the context of eruption and volcano type, instrumentation, eruption recurrence, and the population within 30km. We found that, 19% of the VALs issued between 1990 and 2013 for events that ended with eruption accurately reflect the hazard before eruption. This increases to ~30% if we only consider eruptions with a VEI ? 3. VALs of eruptions from closed-vent volcanoes are more appropriately issued than those from open-vents. These two observations likely reflect the longer and stronger unrest signals associated with large eruptions from closed vents. More appropriate VAL issuance is also found in volcanoes with monitoring networks that are moderately-well equipped (3-4 seismometers, GPS and gas monitoring). There is also a better correlation between VALs and eruptions with higher population density. We see over time (1990 to 2013) that there was an increase in the proportion of `UwE? alerts to other alerts, suggesting increasing willingness to use VALs well before an eruption is certain. The number of accurate VALs increases from 19% to 55% if we consider all UwE alerts to be appropriate. This higher `success? rate for all alerts (with or without eruption) is improving over time, but still not optimal. We suggest that the low global accuracy of the issuance of VALs could be improved by having more monitoring networks equipped to a medium level, but also by using probabilistic hazard management during volcanic crisis.
机译:火山学家使用火山警报等级(VALs)来快速,简单地告知当地居民和政府当局火山动荡和爆发的可能性。大多数VAL并没有明确预测火山活动,但在许多情况下,它们在通知决策中起着重要作用:定义禁区和发布疏散警报。我们对VAL(194次喷发,60座火山)进行了分析,以评估它们在喷发前如何很好地反映动荡,以及哪些其他变量可以控制它们。我们还研究了警报级别增加但没有爆发的​​情况下的VAL,我们将其称为“没有爆发的​​骚动”(UwE)。我们在喷发和火山类型,仪器,喷发复发以及30公里以内人口的背景下分析了我们的结果。我们发现,在1990年至2013年之间针对爆发结束的事件发布的VAL中有19%准确反映了爆发前的危害。如果仅考虑使用VEI喷发的话,这一比例会增加到30%左右。 3.闭口火山喷发的VAL比敞口火山喷发的VAL更合适。这两个观察结果可能反映了与来自封闭通风口的大喷发相关的更长更强的动荡信号。在具有中等装备的监测网络(3-4地震仪,GPS和气体监测)的火山中,也发现了更合适的VAL发行。 VAL与人口密度较高的爆发之间也存在更好的相关性。随着时间的推移(1990年至2013年),我们发现“ UwE?提醒其他提醒,这表明在确定爆发之前就越来越愿意使用VAL。如果我们认为所有UwE警报都适当,则准确的VAL数量将从19%增加到55%。这样更高的成功吗?随着时间的流逝,所有警报(带有或不带有喷发)的速率都在提高,但仍然不是最佳的。我们建议,可以通过在中级水平上配备更多的监控网络,以及通过在火山危机期间使用概率风险管理来改善VAL的全球准确性低下的问题。

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