Marine Works Japan Ltd.

Kanazawa-shi, Japan

Marine Works Japan Ltd.

Kanazawa-shi, Japan

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Morono Y.,Japan Agency for Marine - Earth Science and Technology | Terada T.,Marine Works Japan Ltd | Kallmeyer J.,German Research Center for Geosciences | Inagaki F.,Japan Agency for Marine - Earth Science and Technology
Environmental Microbiology | Year: 2013

Development of an improved technique for separating microbial cells from marine sediments and standardization of a high-throughput and discriminative cell enumeration method were conducted. We separated microbial cells from various types of marine sediment and then recovered the cells using multilayer density gradients of sodium polytungstate and/or Nycodenz, resulting in a notably higher percent recovery of cells than previous methods. The efficiency of cell extraction generally depends on the sediment depth; using the new technique we developed, more than 80% of the total cells were recovered from shallow sediment samples (down to 100 meters in depth), whereas ∼50% of cells were recovered from deep samples (100-365m in depth). The separated cells could be rapidly enumerated using flow cytometry (FCM). The data were in good agreement with those obtained from manual microscopic direct counts over the range 104-108cellscm-3. We also demonstrated that sedimentary microbial cells can be efficiently collected using a cell sorter. The combined use of our new cell separation and FCM/cell sorting techniques facilitates high-throughput and precise enumeration of microbial cells in sediments and is amenable to various types of single-cell analyses, thereby enhancing our understanding of microbial life in the largely uncharacterized deep subseafloor biosphere. © 2013 The Authors. Environmental Microbiology published by John Wiley & Sons Ltd and Society for Applied Microbiology.


Hosoda S.,Japan Agency for Marine - Earth Science and Technology | Ohira T.,Marine Works Japan Ltd. | Sato K.,Japan Agency for Marine - Earth Science and Technology | Suga T.,Japan Agency for Marine - Earth Science and Technology | Suga T.,Tohoku University
Journal of Oceanography | Year: 2010

A global data set describing the gridded mixed-layer depth (MLD) in 10-day intervals was produced using high-quality Argo float data from 2001 to 2009. The characteristics and advantages provided by the new MLD data set are described here, including a comparison based on two different thresholds and using data sets of different vertical and temporal resolution. The MLD in the data set was estimated on the basis of a shallower depth of the iso-thermal layer (TLD) or iso-pycnal layer (PLD), calculated using the finite difference method. The MLD data are incorporated into 2° × 2° grid in the global ocean, including marginal seas. Also, two threshold values were used to examine differences in the MLD and its seasonal temporal variability. The characteristics and advantages of using the Argo 10-day intervals to determine the MLD were then confirmed by comparing those data with the station buoy daily means and the Argo monthly means. With respect to vertical and temporal resolutions, the Argo 10-day data has two distinct advantages: (1) improved representation of the MLD vertical change due to high vertical resolution, especially during periods of large MLD variability and (2) more detailed representation of the temporal change in MLD than achieved with the Argo monthly mean data, especially from winter to spring in mid and high latitudes. These advantages were maintained in the case of a larger threshold despite the fact that the MLD is rather deep and the detailed variation in its distribution differs depending on the season and location. This study also investigated the relative influence of TLD and PLD to the MLD calculation for each grid. Generally, the MLD is primarily determined based on the PLD at low and mid latitudes (TLD > PLD), whereas the TLD is more important at high latitudes, especially in winter (TLD < PLD). In the case of a larger threshold, the area of the larger PLD influence spreads polewards because of the greater effect of salinity in winter. Although there are some differences in the effect of temperature and salinity in estimations of the MLD, both are indispensable factors for the MLD estimations even at different thresholds. © 2010 Springer Science+Business Media B.V.


Kitamura M.,Hiroshima University | Mukoyoshi H.,Marine Works Japan Ltd. | Fulton P.M.,University of Texas at Austin | Hirose T.,Hiroshima University | Hirose T.,Japan Agency for Marine - Earth Science and Technology
Geophysical Research Letters | Year: 2012

The detection of frictional heating effects along faults provides key insight into the dynamics of earthquakes and faulting. Thermal maturity of organic matter has been considered a possible fault-thermometer that records the frictional heat signature of ancient earthquakes. However, whether or not organic matter can mature on the order of seconds, typical earthquake rise time, remains uncertain. Here we present the results of experiments aimed at revealing coal maturation by frictional heat generated at slip velocities representative of natural earthquakes of up to 1.3 m/s. Our results show that coal can mature coseismically in ∼11 seconds at temperatures induced by frictional heat ranging from 26 to 266C. Even with a temperature rise to only 28.7C over 15 m displacement in ∼3.2 hours, coal can slightly mature within a shear localized zone. The commonly used kinetic model of vitrinite maturation cannot predict the experimental results. A kinetic model involving the effect of flash temperature at grain contacts and mechanochemical effects on reaction kinetics is necessary to better estimate heat generation along a fault. © 2012. American Geophysical Union. All Rights Reserved.


Tanikawa W.,Japan Agency for Marine - Earth Science and Technology | Hirose T.,Japan Agency for Marine - Earth Science and Technology | Mukoyoshi H.,Marine Works Japan Ltd. | Mukoyoshi H.,Waseda University | And 2 more authors.
Earth and Planetary Science Letters | Year: 2013

Fluid transport properties such as permeability and porosity are significant parameters that affect earthquake generation. We measured the transport properties of shallow sediments sampled around the plate boundary near the Japan Trench during IODP Expedition 343 at confining pressures up to 40 MPa. The permeabilities of samples from the shallow plate boundary fault were very low at 10 -20m2, equivalent to a hydraulic diffusivity of 10 -10m2s -1. Permeability and porosity in the core of the fault zone at the plate boundary were lower than those in the immediately overlying sediments and the surrounding intact sediment, suggesting that the plate boundary fault can act as a barrier for fluid flow. Low permeability and high pore compressibility in the shallow plate boundary fault create a strong potential for dynamic fault weakening due to fluid pressurization with frictional heating, even when the initial shear stress is low. Our investigation supports the hypothesis that thermal pressurization on the fault plane helped facilitate the extremely large slip in the shallow part of the subduction zone during the Tohoku earthquake. As the fault zone has a lower permeability than the surrounding sediments and a higher clay content, pore pressure generation at depth by dehydration of clay minerals can explain formation of the shallow strong patch on the fault more reasonably than continuous fluid influx from the subducting oceanic crust, which does not affect pore pressure at depth in the fault zone. Although there are many possible mechanisms of fault weakening, thermal pressurization can act relatively efficiently as slip begins, even at shallow depths. Therefore our results support the role of thermal pressurization in shallow slip during the Tohoku earthquake. © 2013 Elsevier B.V.


Honda G.,Osaka University | Ishikawa T.,Japan Agency for Marine - Earth Science and Technology | Hirono T.,Osaka University | Mukoyoshi H.,Marine Works Japan Ltd.
Geophysical Research Letters | Year: 2011

To investigate the slip behavior of a megasplay fault branching from a subduction boundary megathrust, we investigated the geochemistry of an out-of-sequence thrust that formed at 2.5-5.5 km depth. Rocks from the slip zone show major-element and fluid-immobile trace-element compositions that are consistent with disequilibrium flash melting. Distinct depletions of Li, Rb, and Cs in the slip-zone rocks indicate fluid-rock interactions at high temperatures (>350C). These findings suggest a slip process in which high-temperature pore fluids were generated by frictional slip, but the thermally-enhanced pressure might not have reached a sufficient level to cause thermal pressurization, and the temperature continued to increase to attain melting of mica minerals. Comparison with slip zone that formed at a shallower depth (1-2 km), where only thermal pressurization occurred, suggests a transition from melt lubrication at depth to thermal pressurization at shallower depths along a megasplay faults. Copyright 2011 by the American Geophysical Union.


Morono Y.,Japan Agency for Marine - Earth Science and Technology | Terada T.,Marine Works Japan Ltd. | Hoshino T.,Japan Agency for Marine - Earth Science and Technology | Inagaki F.,Japan Agency for Marine - Earth Science and Technology
Applied and Environmental Microbiology | Year: 2014

A prerequisite for DNA-based microbial community analysis is even and effective cell disruption for DNA extraction. With a commonly used DNA extraction kit, roughly two-thirds of subseafloor sediment microbial cells remain intact on average (i.e., the cells are not disrupted), indicating that microbial community analyses may be biased at the DNA extraction step, prior to subsequent molecular analyses. To address this issue, we standardized a new DNA extraction method using alkaline treatment and heating. Upon treatment with 1MNaOH at 98°C for 20 min, over 98% of microbial cells in subseafloor sediment samples collected at different depths were disrupted. However, DNA integrity tests showed that such strong alkaline and heat treatment also cleaved DNA molecules into short fragments that could not be amplified by PCR. Subsequently, we optimized the alkaline and temperature conditions to minimize DNA fragmentation and retain high cell disruption efficiency. The best conditions produced a cell disruption rate of 50 to 80% in subseafloor sediment samples from various depths and retained sufficient DNA integrity for amplification of the complete 16S rRNA gene (i.e., ~1,500 bp). The optimized method also yielded higher DNA concentrations in all samples tested compared with extractions using a conventional kit-based approach. Comparative molecular analysis using real-time PCR and pyrosequencing of bacterial and archaeal 16S rRNA genes showed that the new method produced an increase in archaeal DNA and its diversity, suggesting that it provides better analytical coverage of subseafloor microbial communities than conventional methods. © 2014, American Society for Microbiology.


Tanikawa W.,Japan Agency for Marine - Earth Science and Technology | Sakaguchi M.,Marine Works Japan Ltd. | Tadai O.,Marine Works Japan Ltd. | Hirose T.,Japan Agency for Marine - Earth Science and Technology
Journal of Geophysical Research: Solid Earth | Year: 2010

We measured permeability in sandstone and granite sheared at slip rates from 10-4 to 1.3 m/s under low-normal stress at confining pressures up to 120 MPa. As the slip rate increased, the permeability of Berea sandstone decreased by an order of magnitude, whereas that of Indian sandstone and Aji granite increased by 3 orders of magnitude at high slip rates. A fine-grained gouge layer of thickness developed during slip, and the wear rate was increased abruptly at high slip rates. Microcracks and mesoscale fractures formed at slip rates above 0.13 m/s. Numerical modeling showed that the slip surface temperature increased by several hundred degrees for slip velocities above 0.13 m/s and exceeded the - phase transition temperature of quartz at 1.3 m/s. Both the temperature rise and the temperature gradient at the slip surface were high at fast slip rates. We attributed reduced permeability after slip in porous sandstone to the low-permeability gouge layer. An abrupt permeability increase in low-permeability rocks at high slip rates was caused by heat-induced cracks. An increase in the rate of wear of gouge with increasing slip velocity was caused by frictional heating that reduced the rock strength. The host-rock permeability that separated reductions and increases in permeability was about 10-16 m2 at 10 MPa effective pressure. Our results suggest that abrupt increases in shear stress during slip in a low-permeability fault zone caused by thermal cracking, which may decrease the total slip displacement. The abrupt permeability increase at high slip rates in low-permeability rocks agrees with hydrogeochemical phenomena observed after earthquakes.Copyright 2010 by the American Geophysical Union.


Oguri K.,Japan Agency for Marine - Earth Science and Technology | Harada N.,Japan Agency for Marine - Earth Science and Technology | Tadai O.,Marine Works Japan Co.
Deep-Sea Research Part II: Topical Studies in Oceanography | Year: 2012

We used 210Pb and 137Cs concentrations in twelve cores from the continental shelf and slope of the Bering Sea to investigate recent mass accumulation rates in sediments and sedimentation processes. No decreases in exogenic 210Pb concentrations with depth were observed in sediments from the shallow shelf area, suggesting that there has been considerable mixing of the sediments there. However, we calculated mass accumulation rates from 210Pb ex profiles for several cores collected from the outer shelf and the slope. Mass accumulation rates in the sediments from these cores ranged from 0.11 to 0.44gcm -2y -1. For the cores with a mixed surface layer, we showed that sediments that accumulated over the last 50-78 years were mixed. The 210Pb ex inventories in the sediment cores suggested deposition of 210Pb particles was focused in the slope area. 137Cs was observed in the sediments collected from the northern to western shelf areas. The 137Cs inventories showed higher values in the shelf area, which suggests that fine-grained particles from the Yukon River have contributed to sedimentation there. © 2011 Elsevier Ltd.


Tanikawa W.,Japan Agency for Marine - Earth Science and Technology | Mukoyoshi H.,Marine Works Japan Ltd. | Tadai O.,Marine Works Japan Ltd.
Journal of Structural Geology | Year: 2012

We used a rotary shear apparatus to investigate changes of fluid transport properties in a fault zone by real-time measurement of gas flow rates during and after shearing of hollow sandstone cylinders at various slip rates. Our apparatus measures permeability parallel to the slip plane in both the slip zone and wall rocks. In all cases, permeability decreased rapidly with increasing friction, but recovered soon after slip, reaching a steady state within several tens of minutes. The rate of reduction of permeability increased with increasing slip velocity. Permeability did not recover to pre-slip levels after low-velocity (ca. 0.0019 m/s) tests but recovered to exceed them after high-velocity (ca. 0.29 m/s) tests. Frictional heating of gases at the slip surface increased gas viscosity, which increased gas flow rate to produce an apparent permeability increase. The irreversible permeability changes of the low-velocity tests were caused by gouge formation due to wearing and smoothing of the slip surface. The increase of permeability after high-velocity tests was caused by mesoscale fracturing in response to rapid temperature rise. Changes of pore fluid viscosity contributed more to changes of flow rate than did permeability changes caused by shear deformation, although test results from different rocks and pore fluids might be different. © 2011 Elsevier Ltd.


Ishikawa T.,Japan Agency for Marine - Earth Science and Technology | Nagaishi K.,Marine Works Japan Ltd.
Journal of Analytical Atomic Spectrometry | Year: 2011

We present a methodology for the precise and accurate analysis of boron isotope ratios ( 11B/ 10B) by positive thermal ionization mass spectrometry (P-TIMS) using Cs 2BO 2 + ions. Samples in the form of caesium borate were loaded onto Ta filaments together with graphite and mannitol. The addition of mannitol to the samples is essential to suppress boron volatilization during acid treatment of the samples but is known to lower the performance of P-TIMS. Therefore, the prepared filaments were preheated in an oven at 240 °C to eliminate the mannitol thus stabilizing the chemical species of boron on the filament and increasing the ionization efficiency of Cs 2BO 2 +, which enabled high-precision isotopic analysis of boron with small sample sizes. Analyses of NIST SRM 951 standard showed external reproducibility (2RSD) better than ±0.1‰ for 50-100 ng B and ±0.2‰ for 10 ng B. Ultrafiltration followed by cation- and anion-exchange chromatography was used to chemically separate boron from natural samples. Analyses of coral standard GSJ JCp-1 and seawater standard IRMM BCR-403 gave average δ 11B values of +24.25 ± 0.08‰ and +39.58 ± 0.11‰ (2SD), respectively. The P-TIMS method developed in this study is applicable to a wide field of boron isotopic research that requires high precision and accuracy, including paleo-pH studies using marine carbonate samples. © 2011 The Royal Society of Chemistry.

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