Time filter

Source Type

Minami-rinkan, Japan

Akiyama M.,Hokkaido University of Science | Akiyama M.,Hiroshima University | Shimizu S.,Hiroshima University | Ishijima Y.,Hiroshima University | Naganuma T.,Geoscience Research Laboratory Co.
Limnology | Year: 2010

We estimated the effect of invading Sasa vegetation and accelerated terrestrialization on the microbial community structure in Sarobetsu-genya wetland (SGW) and Nakanominedaira wetland (NW) (original vegetation, Sphagnum). All examined peat-pore water samples were acidic. Electrical conductivity significantly differed between SGW and NW. Nonmetric multidimensional scaling (NMDS) and analysis of similarity based on denaturing gradient gel electrophoresis (DGGE) band patterns revealed differences in the bacterial community structure between the Sasa and Sphagnum vegetations at a depth of 10 cm in NW. In contrast, the bacterial NMDS profiles at all depths differed between the 2 wetlands rather than between the 2 vegetations. The archaeal community structure significantly differed between the wetlands at depths of 30 and 50 cm. The bacterial diversity index derived from the DGGE profiles significantly differed between the wetlands at all depths. The archaeal diversity index significantly differed between the wetlands at a depth of 50 cm. Sasa invasion affected the microbial community structure in the rhizosphere, up to a depth of 10 cm; this effect differed with the terrestrialization speed. These results suggest that in peat bogs subjected to artificially accelerated terrestrialization, the microbial community changes before the occurrence of the natural hydrarch ecological succession involving ground vegetation. © 2010 The Japanese Society of Limnology.

Ohzono M.,Tohoku University | Sagiya T.,Nagoya University | Hirahara K.,Kyoto University | Hashimoto M.,Kyoto University | And 7 more authors.
Geophysical Journal International | Year: 2011

In order to investigate the strain accumulation process around the Niigata-Kobe Tectonic Zone in central Japan, we estimate a precise GPS velocity field around a representative fault area, the Atotsugawa fault system. The velocity profiles obtained from two dense GPS arrays crossing the Atotsugawa fault demonstrate the existence of a laterally heterogeneous deformation pattern along the fault strike. The West Array suggests the possibility of surface fault creep, which disagrees with inferences gleaned from previous EDM measurements. High shear strain rate, which is calculated from wider velocity field, distributes around not only the Atotsugawa fault system, but also the Takayama-Oppara fault zone, which is located 50 km south from the Atotsugawa fault. In order to consider the effect of interaction between those active faults, we conduct a block-fault model analysis. Our block model consists of nine blocks and 33 fault segments. Relative motion between two blocks at the northern and southern ends of the fault system is calculated to be 9.9 mmyr-1. The intervening region between these two blocks corresponds to the Niigata-Kobe Tectonic Zone with a strain rate of 0.2 ppmyr-1. Slip deficit rates at the Atotsugawa, Ushikubi, and Takayama-Oppara fault zones are estimated to be 2.2, 3.9 and 2.3 mmyr-1, respectively. Although the ratio of slip deficit rate (2.2 3.9 2.3 ≈ 1 2 1) of these three faults is similar to that of geological long-term slip rates (1 2 0.7), the magnitude of geodetic slip deficits is 30 per cent to 50 per cent larger than long-term slip rates. This systematic difference may be due to inelastic deformation of the crust in this region. Since the total slip deficit rate between the Ushikubi and the Takayama-Oppara fault zone is 8.4 mmyr-1, about 85 per cent of the relative block motion, the deformation is mostly accommodated by elastic strain accumulation on these three faults. © 2011 The Authors Geophysical Journal International © 2011 RAS.

Akiyama M.,Hokkaido University of Science | Akiyama M.,Geoscience Research Laboratory Co. | Shimizu S.,Hokkaido University of Science | Sakai T.,Hokkaido University of Science | And 3 more authors.
Limnology | Year: 2011

Spatiotemporal variations in microbial gene abundances were investigated to identify potential zones of methanotroph and methanogen biomass in a peat bog in Sarobetsu-genya wetland. The abundances of the bacterial and archaeal 16S rRNA genes, pmoA, and mcrA were 107-109, 107-108, 104-106, and 104-107 copies g-1 dry peat, respectively. Correlation analysis based on microbial gene abundances and environmental factors showed that the spatiotemporal distributions of the abundances of the four microbial genes in peat layers were similar. The mcrA abundance showed a significant negative correlation with the dissolved organic carbon content and a significant positive correlation with the peat temperature. The pmoA abundance was not detectable during the spring thaw when the lowest peat temperature at a depth of 50 cm was recorded. At a depth of 200 cm, the peat temperature exceeded 6°C throughout the year, and the mcrA abundance exceeded 104 copies g-1 dry peat. These results indicate that the seasonal microbial activity related to methane should be evaluated in not only the shallow but also the deep peat layers in order to elucidate the methane dynamics in boreal wetlands. © 2010 The Japanese Society of Limnology.

Fukuda T.,Geoscience Research Laboratory Co. | Takahashi T.,East Nippon Expressway Ltd. | Yamada H.,Konoike Construction Co. | Jiang Y.,Nagasaki University
Harmonising Rock Engineering and the Environment - Proceedings of the 12th ISRM International Congress on Rock Mechanics | Year: 2012

In the design phase of the tunnel, various mechanical constants and their distribution are estimated after comparing research and exploration results with rock mass classification. Based on the estimation, the support pattern is selected and appropriate materials are suggested by numerical analysis, if necessary. In this study, from the perspective of advanced observational construction, we describe the identification of rock physical properties by back analysis and the predictive analysis of long-term deformation of tunnel lining targeting on the tunnel with large deformation. As a result, the most appropriate support pattern was determined by identifying rock physical properties, and an example of long-term predictions of tunnel lining deformation could be presented. © 2012 Taylor & Francis Group, London.

Kawasaki S.,Hokkaido University | Akiyama M.,Geoscience Research Laboratory Co.
Soils and Foundations | Year: 2013

To improve the unconfined compressive strength (UCS) of a novel chemical grout composed of a calcium phosphate compound (CPC-Chem), we performed UCS tests and scanning electron microscopy (SEM) observations on sand test pieces cemented with CPC-Chem and four kinds of powders (tricalcium phosphate, TCP; magnesium phosphate, MgP; calcium carbonate, CC and magnesium carbonate, MgC) as seed crystals. The UCS of the CPC-Chem test pieces cemented with TCP and CC was significantly greater than that of the test pieces with no added powders. The UCS of the test pieces with TCP and CC additives exceeded the targeted value of 100 kPa and increased to a maximum of 261.4 kPa and 209.7 kPa for the test pieces with TCP and CC additives, respectively. Furthermore, the UCS of test pieces with 1 wt% or 5 wt% TCP and 1 wt% CC additives was maintained at a level exceeding 200 kPa for 168 days. SEM observations revealed net-like and three-dimensional structures in segments of test pieces cemented with 1 wt% or 5 wt% TCP and 1 wt% CC in CPC-Chem, which could have been the reason of the long-term stability of UCS (over 200 kPa for 168 days) observed in this study. These results suggest that the addition of TCP and CC significantly enhances the ground improvement afforded by CPC-Chem. © 2013 The Japanese Geotechnical Society.

Discover hidden collaborations