著者

鈴木 建夫 新井田 清信 西田 泰典 大島 弘光 室伏 誠

出版者

北海道大学大学院理学研究院自然史科学部門(地球物理学)

雑誌

北海道大学地球物理学研究報告 (ISSN:04393503)

巻号頁・発行日

vol.70, pp.53-65, 2007-03-15

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Many authors have discussed the eruption time sequence and the mechanism of volcanic eruptions by estimating the ejected velocity of the volcanic blocks, with the aid of other factors of eruptive phenomena. Equations of motion for the volcanic blocks have been proposed by considering the factors, such as the air resistance, the influence of the wind, the inclination of the explosion principal axis and so on. However, the equation of motion and its solution has not been considered that the air resistance power was vector quantity for the flight of volcanic blocks. In this paper a new equation of motion for the ejected volcanic blocks is proposed by considering the air resistance power as vector quantity.

著者

鈴木 建夫 新井田 清信 西田 泰典 大島 弘光 室伏 誠

出版者

北海道大学大学院理学研究院自然史科学部門(地球物理学)

雑誌

北海道大学地球物理学研究報告 (ISSN:04393503)

巻号頁・発行日

vol.70, pp.67-83, 2007-03-15

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The present authors pointed out, in the last paper, a mistake in the equation of motion for volcanic blocks. Reliable assumption of the air resistance to the blocks is required for accurate estimation of initial velocity of volcanic blocks. However, little attention has been given to the point. This paper organizes the problems about the estimation of the air resistance and proposes a new method of the estimation. Also this paper organizes the effect of factors on the distribution of volcanic blocks. Model calculations revealed the effect of the atmospheric air density cannot be ignored. For the effect of explosion principal axis on the distribution of volcanic blocks, this paper proposes an extended equation which volcanic blocks eject to all the directions around the crater.

著者

西田 泰典

出版者

北海道大学大学院理学研究院

雑誌

北海道大学地球物理学研究報告 (ISSN:04393503)

巻号頁・発行日

vol.76, pp.15-86, 2013-03-19

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The self-potential (SP) method is based on measuring the natural electric potential differences, which generally exist between any two points on the ground. The SP fields have their origins in different mechanisms which can be used to identify ore deposits, geological features, ground water flow, and hydrothermal systems. The amplitude has a very wide spectrum, from a few mV/km to a few V/km, and their spatial distribution is correlated with the size of sources that lie at a depth within several hundred meters depth. Despite the fact that SP studies have been carried out by many researchers in the past, especially in field of mine prospecting, the use of the method had been restricted because the sources of SP anomalies were not fully identified and the development of other geophysical methods, such as seismic, electromagnetic and gravimetric methods, was very fast. However, since 1970, the SP method has again risen as a modern prospecting method for delineating the thermal state of geothermal fields. These studies have encouraged the application of the SP method to volcanological, geothermal, hydrological, seismological studies and so on. Spatial and temporal measurements of the SP field may prove to have the advantage of sensing dynamic aspects of the tectonic activities. This article will focus on fundamentals of theoretical and experimental SP studies and will show many field examples to guid for beginners.

著者

大島 弘光 小野 忍 西田 泰典

出版者

北海道大学大学院理学研究科地球惑星科学専攻(地球物理学)

雑誌

北海道大学地球物理学研究報告 (ISSN:04393503)

巻号頁・発行日

vol.67, pp.157-166, 2004-03-15