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Volume 32, Issue 4
Displaying 1-5 of 5 articles from this issue
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Masashige HIRANO1991 Volume 32 Issue 4 Pages 145-154
Published: October 10, 1991
Released on J-STAGE: February 23, 2010
JOURNAL FREE ACCESSSeismic wave refraction data in the rhyoritic (Arima Group) area, north of Osaka, were examined by mirage method. The linear relationship between the subsurface increasing rate k of seismic velocity to the surface velocity V0 is so detected here as in granitic area. Characteristic obliqueness of the iso-velocity surface to the land surface has been derived from the dependence of surface velocities upon the ground slope I and upon the equivalent slope length l. Surface velocity and ground slope get larger following the distance from watershed, and this tendency is hold until the point of l=100m which is the boundary of ridge part to river channel viewed from l-I relationship in the study area. Topographic difference between rhyoritic area and granitic one is shown clearly by this critical distance.
The weathering process near land surface is described approximately by diffusion equation with surface evaporation boundary condition, and this is proved by the proportionality of Laplacian on the density ratio, C=ρ/ρr, to the weathering rate deduced from erosional one, where ρ is apparent density of weathered rock and ρr that of fresh one. Conclusively, the diffusivity constant for rock weathering is estimated to have the order of magnitude of 0.1mm2/year for rhyoritic rock in this area, based on the rate of erosion in the neighbouring Rokko area by slope failures. The value is almost one order smaller than that for granitic rocks, though detailed check of the specific data concerned is the future problem.View full abstractDownload PDF (1536K) -
part 1: Chemical Characteristics of Groundwater and its classification at Ohmine Area in Kamaishi Mine, Iwate Prefecture, JapanSeiya MORITA, Jun SHIMADA, Hisashi CHO1991 Volume 32 Issue 4 Pages 155-166
Published: October 10, 1991
Released on J-STAGE: February 23, 2010
JOURNAL FREE ACCESSThe study of groundwater flow systems in bedrock is very important in assessing the reliability of underground facilities in the deep bedrock.
About the results of examinations now going on in the crystalline bedrock at the Ohmine 550m level drift and KH-1 borehole in the Kamaishi Mine, Iwate prefecture, this paper, part 1, deals with the groundwater chemistry in the deep crystalline bedrock. The Ohmine 550m level drift is located in the northern part of the Kamaishi Mine and Kurihashi granodiorite, Ganidake diorite and skarn minerals are distributed there.
The results of this study are summarized as follows :
1) Water chemistry of the groundwater around the Ohmine 550m level drift in the Kamaishi Mine is classified into six types by Piper's expression, which are also supported other interpretation methods for groundwater chemistry.
2) Water chemistry of the drained groundwater into the drift has some relationship with the fracture distribution frequency of the bedrock.
3) From the results of the multivariate analysis for the groundwater chemistry, the effect of eluviated chemical component from mineralized Ganidake diorite and skarn contribute to the most of the groundwater chemistry in the studied area. Also in the Kurihashi granodiorite, ionic exchange reactions contribute to its groundwater chemistry.View full abstractDownload PDF (2036K) -
Shin KOSHIYA, Ryouji NAGAE, Kazuyoshi OKAMI, Yasuhiko MORITA1991 Volume 32 Issue 4 Pages 167-183
Published: October 10, 1991
Released on J-STAGE: February 23, 2010
JOURNAL FREE ACCESSThe relationship betweeen geological structure and permeability is studied to investigate the movement of the underground water in the Hanawa granite body, distributed in the southwesten part of the Abukuma Plateau.
In the Hanawa granite body, many minor structures are developed, which are mylonitic structure, dykes of pegmatite and aplite, quartz vein, micro-crack and fractures (fault, joint). Among the structures mentioned above, the fractures are significant in the sence of the flow of the underground water, especially in a deeper part.
From the observation in the field, these fractures can be divided into six series clearly, namely A, B, C, D, E and F in the order of formational age, based on the relationships among the fractures. The A (A1 and A2), C (C1 and C2) and F (F1 and F2) series are composed of conjugated sets of faults. On the basis of the geometrical relationship of these conjugate sets of faults, the A series are deduced to be formed under the strike-slip fault type stress field with NW-SE compressional principal stress axis. And both of the C and F series are also deduced to be formed under the N-S tensional stress field.
Statistical analysis of the trends of the fractures and topographic lineaments clarified that the trend is concentrated in NW-SE to NNW-SSE, and it corresponds to the direction of A1, D and F1 type faults.
Taking acount of the geological history from the Cretaceous to the Tertiary age in the Tanakura Shear Zone and adjacent area, the A series were possibly activated during the left lateral movement stage (Cretaceous to Paleogene) of the Tanakura Shear Zone (Koshiya, 1986). And C and F series may be formed in the Miocene.
From the analysis of stress field and period of the activation of the faults, the low permeability in the A1, A2, D and F1 type faults is concluded, and high permeability in the C1, C2 and F2 type faults. The above conclusions is confirmed by the simulation model of FEM and the boring survey performed by the Tohoku Regional Agricultural Administration Office.View full abstractDownload PDF (3326K) -
Akira IWAMATSU1991 Volume 32 Issue 4 Pages 184-187
Published: October 10, 1991
Released on J-STAGE: February 23, 2010
JOURNAL FREE ACCESSDownload PDF (677K) -
Yohta KUMAKI1991 Volume 32 Issue 4 Pages 188-195
Published: October 10, 1991
Released on J-STAGE: February 23, 2010
JOURNAL FREE ACCESSDownload PDF (1375K)
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