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Development of prediction method of volcanic eruption using the synchronism between volcanic activities and the earth and ocean tides.

利用火山活动与地球和海洋潮汐的同步性开发火山喷发预测方法。

基本信息

批准号：
05558048
负责人：
KOYAMA Masato
金额：
$ 4.35万
依托单位：
Shizuoka University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Developmental Scientific Research (B)
财政年份：
1993
资助国家：
日本
起止时间：
1993 至 1994
项目状态：
已结题

项目摘要

This study aimed to examine mechanisms of the synchronism between volcanic activities and the earth and ocean tides, and to evaluate the possibility of a method for predicting volcanic eruptions using the synchronism. For this purpose, we made two approaches : (1) theoretical evaluation of possible mechanisms of the synchronism between volcanic activities and crustal strain including tidal strain ; (2) collection of data of volcanic activities and analysis of the relationships between temporal variations of volcanic activities and variations of tidal force and strain. As for approach (1) , we revealed that crustal strain can generate volcanic activities when the azimuth and amount of the strain give maximum volumetric change to a magma reservoir. This idea is theoretically supported by model calculation and also is demonstrated by the analysis of the relationships between the volcanic earthquakes observed in Izu Oshima Volcano and the crustal strain associated with tectonic earthquakes near the volcano. We also revealed that a cumulative pattern of magma discharge from a volcano can record a history of the eruptions triggered by changes in crustal strain. Concerning approach (2) , we systematically collected historical documents describing the eruptions occurred for the past 1300 years in Izu Oshima Volcano, and revealed that the initiation of the historical eruptions were synchronized with the fortnightly component of the earth tide. We also analyzed the relationships between the tidal strain and the 1991 pyroclastic eruptions in Unzen Volcano and revealed that the tidal strain with an E-W or up-down compressional component triggered large pyroclastic flows during May 24-June 12,1991, when the volcanic activities attained a maximum level. Synthesizing all these results, we clarified problems of the method for predicting volcanic eruptions using the synchronism.

本研究的目的是研究火山活动与地球和海洋潮汐之间的同步性机制，并评估使用同步性预测火山爆发的方法的可能性。为此，我们做了两方面的工作：（1）从理论上探讨火山活动与地壳应变（包括潮汐应变）同步的可能机制;（2）收集火山活动资料，分析火山活动的时间变化与潮汐力和应变变化的关系。对于方法（1），我们揭示了当地壳应变的方位角和应变量使岩浆库的体积变化最大时，地壳应变可以产生火山活动。模型计算从理论上支持了这一观点，并通过分析伊豆大岛火山观测到的火山地震与火山附近构造地震的地壳应变之间的关系得到了证实。我们还发现，从火山喷出的岩浆的累积模式可以记录地壳应变变化引发的喷发历史。关于方法（2），我们系统地收集了描述伊豆大岛火山在过去1300年中发生的喷发的历史文献，并揭示了历史喷发的开始与固体潮的两周分量同步。分析了潮汐应变与1991年云仙火山火山喷发的关系，发现1991年5月24日至6月12日云仙火山活动达到最高峰时，具有东西向或上下挤压分量的潮汐应变触发了大规模火山碎屑流。综合这些结果，我们澄清了使用同步性预测火山喷发的方法的问题。