応用地質
Online ISSN : 1884-0973
Print ISSN : 0286-7737
ISSN-L : 0286-7737
VLF-MT法による火山地域の地質構造探査
富士山北西麓を例にして (2)
河西 秀夫
著者情報
キーワード: VLF-MT法, 火山, 現場測定, 比抵抗
ジャーナル フリー

1994 年 35 巻 3 号 p. 84-92

詳細
抄録

VLF-MT survey was performed over the volcanic ejecta zone in northern foot of Mt. Fuji (Tateishi, Kamiyoshida, Fujiyoshida city, prefecture Yamanashi), and the geological structure is estimated, and the limitationof VLF-MT survey is discussed. This area is characterized by volcanic ejecta (tuff breccia, scoria and so on) resulted from the eruption of Mt. Fuji volcano. The instrument used in this survey is TeraTecnica VL-101equipment.
VLF-MT measurments were made along 14 lines using 50 m station interval, apparent resistivity, phase anglebetween magnetic field and electric field, magnetic field strength and electric field strength are measured ateach station. The value of apparent resistivity of this area ranged in magnitude from 200 ohm-m to 1000 ohm-m.The electric field have considerable variation in value throughout the area, but the magnetic field have little variation.For this reason, the variation of the apparent resistivity has been considered to be due to the variation in theelectric field. When interpreting the structure by two-layer model, evaluation of the resistivity of the top layer pimust to be done. The resistivity of the top layer pi is evaluated by the following manner: value for apparentresistivity at station where has value for phase angle between 43-47 degree is regarded as the value for pi, andthis value is used as pi near the station. The result of the VLF-MT survey is compared with known electrical prospecting data from the same localities.
The result is as follows:
(1) The VLF-MT resistivity profiles are in general agreement with the profiles obtained from the electricalprospecting,
(2) In the VLF-MT survey, multilayer which each layer have similar resistivity value is interpreted as theuniform layer.The result of survey indicate that VLF-MT method is useful for estimating the geological structure in the volcanicarea where no outcrops are present.

著者関連情報
© 日本応用地質学会
次の記事
feedback
Top