Breaking Up: Comminution Mechanisms in Sheared Simulated Fault Gouge   总被引：1，自引：0，他引：1  

K. Mair  S. Abe 《Pure and Applied Geophysics》2011,168(12):2277-2288

The microstructural state and evolution of fault gouge has important implications for the mechanical behaviour, and hence the seismic slip potential of faults. We use 3D discrete element (DEM) simulations to investigate the fragmentation processes operating in fault gouge during shear. Our granular fault gouge models consist of aggregate grains, each composed of several thousand spherical particles stuck together with breakable elastic bonds. The aggregate grains are confined between two blocks of solid material and sheared under a given normal stress. During shear, the grains can fragment in a somewhat realistic way leading to an evolution of grain size, grain shape and overall texture. The ‘breaking up’ of the fault gouge is driven by two distinct comminution mechanisms: grain abrasion and grain splitting. The relative importance of the two mechanisms depends on applied normal stress, boundary wall roughness and accumulated shear strain. If normal stress is sufficiently high, grain splitting contributes significantly to comminution, particularly in the initial stages of the simulations. In contrast, grain abrasion is the dominant mechanism operating in simulations carried out at lower normal stress and is also the main fragmentation mechanism during the later stages of all simulations. Rough boundaries promote relatively more grain splitting whereas smooth boundaries favor grain abrasion. Grain splitting (plus accompanying abrasion) appears to be an efficient mechanism for reducing the mean grain size of the gouge debris and leads rapidly to a power law size distribution with an exponent that increases with strain. Grain abrasion (acting alone) is an effective way to generate excess fine grains and leads to a bimodal distribution of grain sizes. We suggest that these two distinct mechanisms would operate at different stages of a fault’s history. The resulting distributions in grain size and grain shape may significantly affect frictional strength and stability. Our results therefore have implications for the earthquake potential of seismically active faults with accumulations of gouge. They may also be relevant to the susceptibility of rockslides since non-cohesive basal shear zones will evolve in a similar way and potentially control the dynamics of the slide.  相似文献   

Theoretical and experimental investigation of nickel isotopic fractionation in species relevant to modern and ancient oceans     

Toshiyuki Fujii  Frédéric Moynier  Minori Abe 《Geochimica et cosmochimica acta》2011,75(2):469-7643

Nickel plays a central role as an enzyme co-factor in the metabolism of methanogenic Archaea. Methanogens can fractionate Ni isotopes during assimilation, opening the possibility of using the stable isotopic composition of Ni as a biomarker. However, other sources of Ni isotopic variations need to be evaluated before one can establish Ni isotopes as an unambiguous tracer of methanogenesis in the rock record. Equilibrium exchange of Ni between the different species present in the ocean is a potential source of isotopic fractionation. Through controlled laboratory experiments and theoretical calculations, we quantify equilibrium Ni isotope fractionation between different species relevant to the modern and ancient ocean: Ni(H₂O)₆²⁺, Ni(H₂O)₁₈²⁺, NiOH(H₂O)₅⁺, Ni(OH)₂(H₂O)₄, NiCl(H₂O)₅⁺, cis-NiCl₂(H₂O)₄, trans-NiCl₂(H₂O)₄, NiHS(H₂O)₅⁺, Ni(HS)₂(H₂O)₄, NiSO₄(H₂O)₄, NiHCO₃(H₂O)₄⁺, NiCO₃(H₂O)₄, and organic ligands (crown ether and oxalic acid). The magnitude of ligand-controlled Ni isotopic fractionation, approximately 1.25‰/amu (2.5‰ for the ⁶⁰Ni/⁵⁸Ni ratio), is similar to that previously measured in cultures of methanogenic Archaea.  相似文献   

Building damage characteristics based on surveyed data and fragility curves of the 2011 Great East Japan tsunami   总被引：4，自引：2，他引：2  

Anawat Suppasri  Erick Mas  Ingrid Charvet  Rashmin Gunasekera  Kentaro Imai  Yo Fukutani  Yoshi Abe  Fumihiko Imamura 《Natural Hazards》2013,66(2):319-341

A large amount of buildings was damaged or destroyed by the 2011 Great East Japan tsunami. Numerous field surveys were conducted in order to collect the tsunami inundation extents and building damage data in the affected areas. Therefore, this event provides us with one of the most complete data set among tsunami events in history. In this study, fragility functions are derived using data provided by the Ministry of Land, Infrastructure and Transportation of Japan, with more than 250,000 structures surveyed. The set of data has details on damage level, structural material, number of stories per building and location (town). This information is crucial to the understanding of the causes of building damage, as differences in structural characteristics and building location can be taken into account in the damage probability analysis. Using least squares regression, different sets of fragility curves are derived to demonstrate the influence of structural material, number of stories and coastal topography on building damage levels. The results show a better resistant performance of reinforced concrete and steel buildings over wood or masonry buildings. Also, buildings taller than two stories were confirmed to be much stronger than the buildings of one or two stories. The damage characteristic due to the coastal topography based on limited number of data in town locations is also shortly discussed here. At the same tsunami inundation depth, buildings along the Sanriku ria coast were much greater damaged than buildings from the plain coast in Sendai. The difference in damage states can be explained by the faster flow velocities in the ria coast at the same inundation depth. These findings are key to support better future building damage assessments, land use management and disaster planning.  相似文献   

Modeling the potential distribution of shallow-seated landslides using the weights of evidence method and a logistic regression model： a case study of the Sabae Area, Japan   总被引：5，自引：0，他引：5  

Ru-Hua SONG  Daimaru HIROMU  Abe KAZUTOKI  Kurokawa USIO  Matsuura SUMIO 《国际泥沙研究》2008,23(2):106-118

A number of statistical methods are typically used to effectively predict potential landslide distributions. In this study two multivariate statistical analysis methods were used （weights of evidence and logistic regression） to predict the potential distribution of shallow-seated landslides in the Kamikawachi area of Sabae City, Fukui Prefecture, Japan. First, the dependent variable （shallow-seated landslides） was divided into presence and absence, and the independent variables （environmental factors such as slope and altitude） were categorized according to their characteristics. Then, using the weights of evidence （WE） method, the weights of pairs comprising presence （w^＋（i）） or absence （w^-（i））, and the contrast values for each category of independent variable （evidence）, were calculated, Using the method that integrated the weights of evidence method and a logistic regression model, score values were calculated for each category of independent variable. Based on these contrast values, three models were selected to sum the score values of every gird in the study area. According to a receiver operating characteristic curve analysis （ROC）, model 2 yielded the best fit for predicting the potential distribution of shallow-seated landslide hazards, with 89% correctness and a 54.5% hit ratio when the occurrence probability （OP） of landslides was 70%. The model was tested using data from an area close to the study region, and showed 94% correctness and a hit ratio of 45.7% when the OP of landslides was 70%. Finally, the potential distribution of shallow-seated landslides, based on the OP, was mapped using a geographical information system.  相似文献   

Climate control on Venus: Comparison of the carbonate and pyrite models     

George L. Hashimoto  Yutaka Abe 《Planetary and Space Science》2005,53(8):839-848

We review two models describing the Venus climate system: the carbonate and pyrite models. It has been argued carbonate and pyrite are potentially important minerals controlling the climate of Venus, though existence of either minerals has not been confirmed. Although it used to be proposed that carbonation reaction might explain the Venus’ atmospheric CO₂ abundance, it is unlikely Venus’ surface is reactive enough to control the Venus’ massive CO₂ atmosphere. Venus’ surface carbonate is also able to affect the climate through the reaction with atmospheric SO₂ to form anhydrite. Under the carbonate model the climate state is not in equilibrium and would be unstable due to the reaction between carbonate and SO₂. On the other hand, pyrite-magnetite reaction is proposed to explain the Venus’ atmospheric SO₂ abundance. Under pyrite-magnetite reaction, however, the climate would be stabilized such that the existing climate state is maintained over a geological timescale, while some observational facts such as atmospheric abundance of SO₂ and surface temperature could also be reasonably explained.  相似文献   

Cd adsorption onto Pseudomonas putida in the presence and absence of extracellular polymeric substances   总被引：1，自引：0，他引：1  

Masato Ueshima 《Geochimica et cosmochimica acta》2008,72(24):5885-5895

The role of bacterial extracellular polymeric substances (EPS) in metal adsorption was determined by studying Cd adsorption onto the gram-negative bacterial species Pseudomonas putida with and without enzymatic removal of EPS from the biomass material. A range of experimental approaches were used to characterize the Cd adsorption reactions, including bulk proton and Cd adsorption measurements, FTIR spectroscopy, and fluorescence microscopy. The proton-reactivities of the biomass samples with EPS are not significantly different from those obtained for EPS-free biomass. Similarly, the presence of EPS does not significantly affect the extent of Cd removal from solution by the biomass on a mass-normalized basis, based on bulk Cd adsorption measurements conducted as a function of pH, nor does it appear to strongly affect the Cd-binding groups as observed by FTIR. However, fluorescence microscopy indicates that Cd, although concentrated on cell walls, is also bound to some extent to EPS. Together, the results from this study suggest that the P. putida EPS can bind significant concentrations of Cd from solution, and that the nature and mass-normalized extent of the binding is similar to that of the cell wall. Therefore, the EPS-bearing systems do not exhibit enhanced mass-normalized removal of Cd from solution relative to the EPS-free systems. The presence of the EPS effectively increases the viability of cells exposed to aqueous Cd, likely due to sequestration of the Cd away from the cells due to Cd-EPS binding.  相似文献   

Effect of temperature on the methyl chloride production rate in a marine phytoplankton, <Emphasis Type="Italic">Phaeodactylum tricornutum</Emphasis>     

Minami?Abe  Takahiro?Nagai  Michiko?Kurihara  Shinya?HashimotoEmail author 《Journal of Atmospheric Chemistry》2017,74(2):157-169

Methyl halides such as methyl chloride (CH₃Cl) are known to be important carriers of halogen from the ocean to the atmosphere, and the halogens they release into the stratosphere by photolysis catalyze ozone depletion. Marine phytoplankton have been reported as a source of CH₃Cl, but the effects of environmental temperature on the CH₃Cl production by phytoplankton have not been investigated. In this study, we investigated the effects of temperature on the production of CH₃Cl in the culture of a marine diatom, Phaeodactylum tricornutum CCMP 630, incubated at 10, 15, 20, 25, and 30 °C. CH₃Cl concentrations in cultured samples were determined using purge and trap gas chromatograph–mass spectrometry. Phytoplankton growth was monitored by measuring the chlorophyll a concentrations. CH₃Cl production was observed for several weeks at four different temperatures ranging from 10 to 25 °C. The CH₃Cl production from P. tricornutum was increased with increasing temperature from 10 to 25 °C, and the maximum production rate for CH₃Cl was 0.21~0.26 μmol (g chlorophyll a)^?1 d^?1 at 25 °C, which was several times higher than that at 10 °C (~0.03 μmol (g chlorophyll a)^?1 d^?1). The Arrhenius equation was successfully used to characterize the effects of temperature on the production rates of CH₃Cl in the culture of P. tricornutum. Our results suggest that water temperature directly affects CH₃Cl production derived from P. tricornutum and that water temperature would be a significant factor for estimating the emissions of CH₃Cl from marine environments.  相似文献   

Primary productivity at the time-series stations in the northwestern Pacific Ocean: is the subtropical station unproductive?     

Kazuhiko Matsumoto  Osamu Abe  Tetsuichi Fujiki  Chiho Sukigara  Yoshihisa Mino 《Journal of Oceanography》2016,72(3):359-371

  相似文献   

Current structure and volume transport of the Soya Warm Current in summer     

Masaji Matsuyama  Makiko Wadaka  Taizo Abe  Masaaki Aota  Yoshio Koike 《Journal of Oceanography》2006,62(2):197-205

ADCP, CTD and XBT observations were conducted to investigate the current structure and temperature, salinity and density distributions in the Soya Warm Current (SWC) in August, 1998 and July, 2000. The ADCP observations clearly revealed the SWC along the Hokkaido coast, with a width of 30–35 km and an axis of maximum speed of 1.0 to 1.3 ms⁻¹, located at 20–25 km from the coast. The current speed gradually increased from the coast to a maximum and steeply decreased in the offshore direction. The SWC consisted of both barotropic and baroclinic components, and the existence of the baroclinic component was confirmed by both the density front near the current axis and vertical shear of the alongshore current. The baroclinic component strengthened the barotropic component in the upper layer near the axis of the SWC. The volume transport of the SWC was 1.2–1.3 SV in August, 1998 and about 1.5 SV and July, 2000, respectively. Of the total transport, 13 to 15% was taken up by the baroclinic component. A weak southeastward current was found off the SWC. It had barotropic characteristics, and is surmised to be a part of the East Sakhalin Current.  相似文献   

Stable isotope and chemical composition of pearls: Biomineralization in cultured pearl oysters in ago bay, Japan     

Hodaka Kawahata  Mayuri Inoue  Masato Nohara  Atsushi Suzuki 《Journal of Oceanography》2006,62(4):405-412

The δ¹⁸O, δ¹³C and trace element composition of pearls collected from Ago Bay, Japan, were investigated in order to evaluate biomineralization in the cultured pearl oyster (Pinctada fucata martensii). The oxygen isotopic data suggest that the pearls were produced around 23–24°C, mainly in June to early July, which is consistent with their occurrence in the field. Therefore the pearls were produced under or close to isotopic equilibrium conditions, although they showed high calcification rates (higher than 0.2–1.0 g cm^{− 2}yr⁻¹) under which, for example, coral skeletons (calcification rate ∼0.28 g cm^{− 2}yr⁻¹) often show non-equilibrium isotope partitioning. The δ¹³C values were ∼− 2.9‰ lower than those calculated for offshore waters under equilibrium conditions. This may be due to low-δ¹³C bottom waters resulting from the degradation of organic matter (OM) or to a contribution of low-δ ¹³C food. In the latter case, a simple mass balance calculation gives a respiration component of 14%. Twelve trace elements of bulk pearl samples were classified into four groups on the basis of their enrichment/depletion patterns relative to seawater and inter-element relationships: group 1, Co, Cr, Pb; group 2, Ba, Cs, U; group 3, Cu, Sn, V, and group 4, Mn, Rb, Mo. Comparison with coral skeletons suggests that Ba and Mn (groups 2 and 4) were definitely much enriched in proteinaceous OM relative to aragonite crystals in pearls and that V (group 3) in pearls showed only slight enrichment in the organicrich layer. By contrast, the other elements showed small differences between both layers (enrichment factor of <3), suggesting that these elements occur largely in aragonite crystals.  相似文献