Study on the Magma-External Water Interaction

为了研究火山岩浆爆炸的机理和预测伴随爆炸的灾害分布，我们做了以下几个方面的研究工作：(1)火山爆炸产生的爆炸和火山碎屑浪涌压力的测量仪器的研制；(2)利用我们研制的仪器对阿索火山爆炸的观测和爆炸能量的测量；(3)建立爆炸能量与伴随火山爆炸的地质和灾害分布的定标规则。(4)建立了解释岩浆-水相互作用的情景。我们研制的观测系统主要由压电式压力传感器、热电偶、数字示波器和个人计算机组成。我们开始使用这个系统观测阿索火山的火山爆发。为了实现研究(3)，我们进行了现场爆炸实验，发现爆炸能量与地质灾害分布之间建立了立方根标度定律，只要知道一个与火山爆炸直接相关的参数，如爆炸能量和火山口直径，就可以预测分布。对于研究点(4)，我们提出了一种新的情景(对于岩浆-吸水器相互作用的情况)，解释了发生在浅层地下的岩浆爆炸。在这种情况下，我们指出，吸水剂的液化对于相互作用是必不可少的；极快地产生蒸汽。

In order to investigate the mechanism of a phreatomagmatic explosion and to predict the distribution of disaster accompanied by the explosion, we have made an effort to accomplish the following research points.(1) Development of the instruments for measuring the pressures of blast and pyroclastic surge produced by the volcanic explosion, (2) observation of the explosion and measurement of the explosion energy at Aso Volcano using the instruments we developed, (3) establishment of the scaling rule which relate the explosion energy to geological and disaster distributions accompanied by the volcanic explosions, (4) and making a scenario which interpret the magma-external water interactions.The system for the observation we developed consists mainly of piezo-pressure sensors, thermo-couple, degital-oscilloscope and a personal-computer. We began to observe the volcanic explosions at Aso Volcano using this system. To fulfilll the research point (3), we have made a field explosion experiment, and found that the cube-root scaling law established between the explosion energy and geological and disaster distributions ; we can predict the distributions if we know one parameter which relate directly to the volcanic explosion such as the explosion energy and crater diameter. For the research point (4), we presented a new scenario (for the case magma-aquifier interaction) which interpret the phreatomagmatic explosion occured in shallow underground. In this case we pointed out that the liquification of aquifier is essential for the interaction ; extremely rapid generation of vapor.