All issues
Volume 50, Issue 1
Displaying 1-3 of 3 articles from this issue
- |<
- <
- 1
- >
- >|
Original Article
-
Ken HASEGAWA, Toshiyuki MATSUOKAArticle type: Original Article
2009 Volume 50 Issue 1 Pages 2-15
Published: April 10, 2009
Released on J-STAGE: February 24, 2012
JOURNAL FREE ACCESSApplicability of aeromagnetic survey to weak magnetic anomaly area was tested. The target is the Toki granite area known as the Ryoke belt. Total of 95 traverse lines 38km long were flown at the altitude of 400m above ground with the line spacing of 400m.
After the data compilation and diurnal correction, the altitude reduction procedure was applied by means of the ‘equivalent source’ method.
The result revealed a magnetic anomaly possibly caused by the Toki granite. To make clear the cause of this anomaly, magnetic susceptibility measurement of rock samples of the Toki granite from some boreholes were conducted. The results of this measurement indicated that the Toki granite can be divided into two zones from the view point of magnetic susceptibility: one zone has relatively high magnetic susceptibility (2×10-3(SI)), while the other has quite low magnetic susceptibility (5×10-5(SI)).
Taking into account of this result, we conducted a 3-D modeling describing the shape of higher magnetic susceptibility part of the Toki granite, which could explain most of the aeromagnetic survey data.
Final data also show additional magnetic information, such as the natural remanent magnetization (NRM) of the Hachiya and Nakamura formation in the Kani basin and unknown intrusive rock beneath the Mino sedimentary complex rock area.
Our approach shows that an aeromagnetic survey can be used to determine geological structures even for weak magnetic anomaly areas such as the Ryoke belt.View full abstractDownload PDF (3091K) -
- A Case Study of ‘Damaged Zone’ Analysis on Atera Fault, Central Japan -Hidekazu YOSHIDA, Akihiro OSHIMA, Kumiko YOSHIMURA, Akio NAGATOMO, Sho ...Article type: Original Article
2009 Volume 50 Issue 1 Pages 16-28
Published: April 10, 2009
Released on J-STAGE: February 24, 2012
JOURNAL FREE ACCESSFault is inevitably associating the ‘damaged zone’ with fracturing along the fault plane. The distribution characteristics of fractures in the ‘damaged zone’ are considered to be reflecting the process of faulting and also to be used for understanding the influence of fault movement in the surrounding host rocks during the fault development. In order to understand such relation between fault movement and formation of ‘damaged zone’, the fracture density and its morphological feature along Atera fault distributed in Gifu prefecture, central Japan have been investigated. The result of detailed fracture mapping of the fractures in the ‘damaged zone’ shows that the fractures formed by faulting can be distinguished from those primarily developed in the host rock by its morphological features and the difference of fracture filling minerals. In particular, shortly transected network type fractures filled by iron-oxides have been preferentially formed in the ‘damaged zone’ along the Atera fault probably induced by fault movement. The density of fractures also suggests that the ‘damaged zone’ formed by fault movement is distributed up to ca. 200 meters from the fault plane. The results provide an idea that the detailed characterization of fractures and fracture fillings can be used to estimate the area of ‘damaged zone’developed along a fault, and the methodology is applicable to the site characterization and allocation of underground facilities such as a radioactive waste repository in crystalline rocks.View full abstractDownload PDF (2637K)
Short Report
-
Takaaki WAJIMA, Yasuyuki IKEGAMIArticle type: Short Report
2009 Volume 50 Issue 1 Pages 29-34
Published: April 10, 2009
Released on J-STAGE: February 24, 2012
JOURNAL FREE ACCESSAt geothermal plant, the geothermal water after separation contains high level of As over Japanese effluent standard level and much silica to cause silica scale. In order to establish the effective utilization system for geothermal resources, we tried to remove As and silica from geothermal water, simultaneously, using inorganic anion exchanger, hydrotalcite. The treatment of geothermal water with hydrotalcite could remove As and silica, simultaneously, and As and silica concentrations dropped to below Japanese effluent standard level (0.1mg/l) and the level to prevent silica scale (100mg/l), respectively, in the range of temperature between 25°C and 80°C. Calcined hydrotalcite indicated more effective removals of As and silica than non-calcined hydrotalcite. The residue after the treatment mostly retained As and silica, which was removed from geothermal water, by heating at 60°C.View full abstractDownload PDF (801K)
- |<
- <
- 1
- >
- >|