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Volume 119, Issue 2
Displaying 1-8 of 8 articles from this issue
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SPECIAL ISSUE Interplay between structural geology and applied geology
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2013 Volume 119 Issue 2 Pages 57-58
Published: 2013
Released on J-STAGE: May 28, 2013
JOURNAL FREE ACCESSDownload PDF (194K)
Review
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Tadahiko Tsuruta, Masahiko Tagami, Kenji Amano, Toshiyuki Matsuoka, Ar ...2013 Volume 119 Issue 2 Pages 59-74
Published: February 15, 2013
Released on J-STAGE: May 28, 2013
JOURNAL FREE ACCESSJapan Atomic Energy Agency (JAEA) is performing a geoscientific research project, the Mizunami Underground Research Laboratory (MIU) project, in order to establish scientific and technological basis for geological disposal of high-level radioactive wastes. The MIU is located in crystalline rock environment, in Mizunami City, central Japan. Field investigations include geological mapping, reflection seismic surveys, several borehole investigations and geological investigations in the research galleries to identify the distribution and heterogeneity of fractures and faults that are potential major flowpaths for groundwater. The results of these field investigations are synthesized and compiled for the purpose of geological modeling. The field investigations indicate that the Main Shaft at the MIU intersected low permeability NNW oriented faults. A high permeability fracture zone in the granite, a significant water inflow point, was observed in the Ventilation Shaft. Development of the geological model focusing 3D spatial relationships at different scales and evolution of the geoenvironment are underway. This paper describes geological investigations applied in the MIU project, focusing on the evaluation of their effectiveness to understand for deep underground geoenviroment.View full abstractDownload PDF (13476K) -
Shinji Takeuchi, Hiromitsu Saegusa, Kenji Amano, Ryuji Takeuchi2013 Volume 119 Issue 2 Pages 75-90
Published: February 15, 2013
Released on J-STAGE: May 28, 2013
JOURNAL FREE ACCESSSeveral hydrogeological investigation techniques have been used at the Mizunami Underground Research Laboratory site to assess hydrogeological structures and their control on groundwater flow. For example, the properties of water-conducting features (WCFs) can be determined using high-resolution electrical conductivity measurements of fluids, and compared to measurements using conventional logging techniques. Connectivity of WCFs can be estimated from transmissivity changes over time, calculated from the pressure derivative of hydraulic pressure data obtained from hydraulic testing results. Hydraulic diffusivity, obtained from hydraulic interference testing by considering the flow dimension, could be a key indicator of the connectivity of WCFs between boreholes. A conceptual hydrogeological model of several hundred square meters to several square kilometers, bounded by flow barrier structures, has been developed from pressure response plots, based on interference hydraulic testing. The applicability of several methods for developing conceptual hydrogeological models has been confirmed on the basis of the hydrogeological investigation techniques mentioned above.View full abstractDownload PDF (5994K) -
Bunichiro Shibazaki2013 Volume 119 Issue 2 Pages 91-104
Published: February 15, 2013
Released on J-STAGE: May 28, 2013
JOURNAL FREE ACCESSTo understand the generation processes of large earthquakes inland of convergent margins, it is necessary to investigate the tectonic loading processes caused by interactions of plates along plate boundaries, and internal inelastic deformation and fault processes within island arc crust and uppermost mantle. Internal deformation and faulting processes are controlled by non-uniform rheological structures in the island arc crust and the uppermost mantle. This paper reviews studies using numerical models to describe deformation and faulting processes in the crust in the Ou Backbone range (OBR) and the mid-Niigata region, by accounting for the non-uniform rheological structures in the island arc crust. Models of fault processes in these areas must consider non-uniform distributions of viscosity and frictional strength. Beneath the OBR, crustal rocks are thought to have been more weakened than those in surrounding areas because of the presence of aqueous fluids and high temperatures associated with volcanic activity. A theoretical study demonstrates that shortening deformation due to nonlinear viscous flow occurs in the high-temperature section of the lower crust, resulting in shear faulting in the upper crust. On the other hand, it is generally considered that many inland earthquakes occur along pre-existing normal faults formed in a pre-existing rift system within a back-arc region during the opening of the Japan Sea (25–15 Ma); these faults were reactivated as reverse faults during the shortening deformation that has occurred since 3.5 Ma. The numerical models confirm that ancient rift structures and weak zones in the basement caused the development of the complex fault configurations associated with the 2004 and 2007 earthquakes in the mid-Niigata region. The development of models for the generation processes of large inland earthquakes requires an understanding of the realistic rheological structures which depend on the tectonic settings of the model region.View full abstractDownload PDF (6326K) -
Shinji Toda2013 Volume 119 Issue 2 Pages 105-123
Published: February 15, 2013
Released on J-STAGE: May 28, 2013
JOURNAL FREE ACCESSSeveral large inland earthquakes in Japan since the 1995 Hygokennambu (Kobe) earthquake have struck the lower probability areas mapped by the Earthquake Research Committee (ERC) of the Headquarters for Earthquake Research Promotion in 2005. To seek the reason why it appears to have failed, here we re-examined the surface-rupturing earthquakes since 1923 when the Japan Meteorological Agency (JMA) officially started their catalog recording. Only 20% of M ≥ 6.5 and 44% of M ≥ 7.0 shallow earthquakes left the surface breaks that correspond to their source fault dimension. We thus speculate that the number of potential destructive earthquakes of M6-7 estimated from the major active faults would be significantly underestimated. Numerical calculations with active fault data and their assigned probabilities in the report also largely underestimate the number of observed earthquakes. Both independent analyses suggest that there would be far more minor active faults hidden beneath Japanese islands. From a viewpoint of elastic rebound in different scales, we discuss efficiency of stress release associated with inland earthquakes and maldistribution of active faults. Simple elastic half-space models qualitatively demonstrate that highly dipping reverse faulting earthquakes such as the 2004 Niigata-ken-Chuetsu earthquake associated with tectonic inversion are unfavorably oriented for the recent stress field and inefficient to release regional differential stress. The models also imply that numerous moderate-size earthquakes due to minor faults cannot compensate one large earthquake caused by a mature fault system. It explains that the inland deformation zone sustains high continuous seismicity, whereas the outer zone facing the Pacific Ocean is significantly influenced by the seismic cycles of subduction mega-thrust events. Regarding to the probabilistic estimates of large earthquakes, the former would be appropriate for more Poisson forecasting taking bulk deformation into account, and the latter would be evaluated from time-dependent conditional probabilities.View full abstractDownload PDF (6338K) -
Toshiyuki Tosha, Yasuko Okuyama, Tsuneo Ishido2013 Volume 119 Issue 2 Pages 124-138
Published: February 15, 2013
Released on J-STAGE: May 28, 2013
JOURNAL FREE ACCESSDue to growing concerns about increasing atmospheric CO2 concentrations, urgent development of carbon capture and storage (CCS) technology is necessary. The 1996 Protocol to the London Convention became effective in 2006, and prohibited CO2 storage in deep ocean masses. This means that the only viable option for CCS is storage in geological formations. One option for geological CCS is in depleted oil or gas reservoirs, which have closure structures that could retain oil or gas over geological time scales, and are relatively easy to with technologies developed for enhanced oil and gas recovery. Such oil or gas reservoirs suitable for CCS are, however, scarce around the islands of Japan. In contrast, storage in deep saline aquifers may be an option due to their large capacity. This type of storage was first attempted in the Sleipner area of the North Sea. The aquifer storage option is particularly promising for CCS in Japan, as appropriate geological formations are common around the islands of Japan. Offshore saline aquifers with a large storage capacity might be particularly suitable for large emission sources, such as thermal electricity generation plants and steel refineries located in coastal regions.
We review several important geological case studies of CO2 storage, including the Iwanohara Pilot Plant, which is the first onshore example of geological CCS. We also briefly present results of a numerical simulation study based upon a conceptual CCS model for the coastal aquifers underlying the Tokyo Bay area, and a summary of the relevant legislation for geological CCS in Japan.View full abstractDownload PDF (6260K) -
Masao Sorai2013 Volume 119 Issue 2 Pages 139-152
Published: February 15, 2013
Released on J-STAGE: May 28, 2013
JOURNAL FREE ACCESSThis paper reviews recent research on geochemical processes related to CO2 sequestration in geological formations. Injection of CO2 into deep saline aquifers initiates a series of geochemical processes, starting with the acidification of formation water (caused by CO2 dissolution) and resultant reactions with surrounding rocks. These processes ensure the stability of CO2 storage through the transfer of free CO2 phases to various less mobile phases (e.g., carbonic acids and carbonate minerals) over long time scales; however, the geochemical transformations may impact the integrity of the injection wells, and the CO2 injection capacity of formations around the wellbore, during operations. Several approaches, using laboratory experiments, natural analogues, field demonstration tests, and numerical modeling, are available for geochemical assessments of the impacts of CO2 injection. Among these, two- and three-dimensional reactive transport modeling are common mainstream approaches. Reactive transport modeling has contributed to an understanding of the geochemical aspects of CO2 injection; however, the approach is plagued by uncertainties, particularly regarding the kinetics of CO2−water−rock inter-actions. To remedy this situation and improve the reliability of modeling results, accurate data on thermodynamic and kinetic parameters, derived from laboratory and field studies, are required. Past studies have focused on assessments of geochemical processes caused by geological sequestration of CO2. Future efforts should pay attention to active applications of these geochemical processes, to improve storage stability, economic costs, and public acceptance, and to minimize environmental impacts.View full abstractDownload PDF (1480K)
Pictorial
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Tadahiko Tsuruta, Shinji Takeuchi2013 Volume 119 Issue 2 Pages III-IV
Published: February 15, 2013
Released on J-STAGE: May 28, 2013
JOURNAL FREE ACCESSDownload PDF (4064K)
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