Generation of electromotive force in igneous rocks subjected to non-uniform loading          下载免费PDF全文

Akihiro Takeuchi  &#  mer Aydan  Keizo Sayanagi  Toshiyasu Nagao 《地震科学（英文版）》2011,24(6):593-600

When one end of an air-dry igneous rock block was uniaxially loaded in laboratory, there appeared an electromotive force that made electric currents flow from the stressed volume to the unstressed volume. Quartz-free rocks such as gabbro also generated this force, stronger than quartz-bearing rocks such as granite. This indicates that the piezoelectric effect of quartz and the electrokinetic effect of pore water do not make a large contribution toward generating the electromotive force. We focus on peroxy bond that is one of the abundant lattice defects in igneous rock-forming minerals. When mechanical loading deforms the lattice structure around this defect and breaks its bond, its energy levels change and act like an accepter. As an electron is trapped at this defect from a neighbor O^2- site, a positive hole is activated there. They attempt to diffuse toward the unstressed volume through the valence band and are simultaneously affected by the attractive electric force with the electrons trapped in peroxy bonds. This leads to a polarization in the stressed volume and the generation of electromotive force between the stressed and unstressed volumes. Similar electromotive force may be generated in the Earth's crust where inhomogeneous stress/strain is changing.  相似文献   

U–Th dating of carbonate nodules from methane seeps off Joetsu, Eastern Margin of Japan Sea     

Yumiko Watanabe  Shun'ichi Nakai  Akihiro Hiruta  Ryo Matsumoto  Kunio Yoshida 《Earth and Planetary Science Letters》2008,272(1-2):89-96

We performed U–Th radioactive disequilibrium analyses of carbonate nodules and sediment samples recovered from methane seep sites off Joetsu, of the eastern margin of Japan Sea, to decipher the active period of the methane seep. The carbonates contain ²³⁰Th, part of which is located in detritus such as silicate and organics, at the time of precipitation. The initial ²³⁰Th renders accurate dating with U–Th radioactive disequilibrium method difficult. We assessed the feasibility of correction using radioactive disequilibrium data of ambient sediment to overcome this difficulty. A (²³⁰Th/²³²Th)–(²³⁴U/²³²Th) isochron drawn by three chips divided from a carbonate nodule (PC05-04-50) passed through data points of local sediments. We conclude that the problem of initial ²³⁰Th can be resolved by measurements of local sediments. Results show that carbonate nodules include local sediment as impurities. Furthermore, the results of trace element analyses such as Rb, Zr, Nb, REE, Pb, and Th also support the idea.In all, 18 carbonate samples were dated with correction of initial ²³⁰Th using the mean value of local sediment in this study. The U–Th correction ages show 12–35ka with an isochron age of 26 ± 3ka. Results indicate that during the time interval of U–Th ages, from 12ka to 35ka, environmental conditions must have been favorable for enhanced methane flux through sediment. The extensive methane flow period at 20ka accords with the lowest-stand sea level during the last glacial age. Results of this study also suggest that U–Th ages of carbonate are useful as a reliable chronometer with regard to methane seep activation. In order to acquire U–Th ages of carbonate at methane seep sites, however, it is important to evaluate the amount of initial ²³⁰Th accurately using the value of sediment.  相似文献   

Density variations of Cr-rich garnets in the upper mantle inferred from the elasticity of uvarovite garnet     

Steeve Gréaux  Akihiro Yamada 《Comptes Rendus Geoscience》2019,351(2-3):95-103

The thermoelastic parameters of Ca₃Cr₂Si₃O₁₂ uvarovite garnet were examined in situ at high pressure up to 13 GPa and high temperature up to 1100 K by synchrotron radiation energy-dispersive X-ray diffraction within a 6-6-type multi-anvil press apparatus. A least-square fitting of room T data to a third-order Birch–Murnaghan (BM3) EoS yielded K₀ = 164.2 ± 0.7 GPa, V₀ = 1735.9 ± 0.3 ų (K’₀ fixed to 4.0). P–V–T data were fitted simultaneously by a modified HT-BM3 EoS, which gave the isothermal bulk modulus K₀ = 163.6 ± 2.6 GPa, K’₀ = 4.1 ± 0.5, its temperature derivative (?K_0,T/?T)_P = –0.014 ± 0.002 GPa K^?1, and the thermal expansion coefficients a₀ = 2.32 ± 0.13 ×10^?5 K^?1 and b₀ = 2.13 ± 2.18 ×10^?9 K^?2 (K’₀ fixed to 4.0). Our results showed that the Cr³⁺ enrichment in natural systems likely increases the density of ugrandite garnets, resulting in a substantial increase of mantle garnet densities in regions where Cr-rich spinel releases chromium through a metasomatic reaction.  相似文献   

Forces acting on bridge abutments over liquefied ground     

Akihiro Takahashi  Hideki Sugita  Shunsuke Tanimoto 《Soil Dynamics and Earthquake Engineering》2010

Large earthquake-induced displacements of a bridge abutment can occur, when the bridge is built on a floodplain or reclaimed area, i.e., liquefiable ground, and crosses a water channel. Seismic responses of a bridge abutment on liquefiable ground are the consequence of complex interactions between the abutment and surrounding soils. Therefore identification of the factors dominating the abutment response is important for the development of simplified seismic design methods. This paper presents the results of dynamic three-dimensional finite element analyses of bridge abutments adjacent to a river dike, including the effect of liquefaction of the underlying ground using earthquake motions widely used in Japan. The analysis shows that conventional design methods may underestimate the permanent abutment displacements unless the following two items are considered: (1) softening of the soil beneath the liquefiable layer, due to cyclic shearing of the soil surrounding the piles, and (2) the forces acting on the side faces of the abutment.  相似文献   

Study on the fate of petroleum-derived polycyclic aromatic hydrocarbons (PAHs) and the effect of chemical dispersant using an enclosed ecosystem,mesocosm     

Yamada M  Takada H  Toyoda K  Yoshida A  Shibata A  Nomura H  Wada M  Nishimura M  Okamoto K  Ohwada K 《Marine pollution bulletin》2003,47(1-6):105-113

Polycyclic Aromatic Hydrocarbons (PAHs) are one of the components found in oil and are of interest because some are toxic. We studied the environmental fate of PAHs and the effects of chemical dispersants using experimental 500 l mesocosm tanks that mimic natural ecosystems. The tanks were filled with seawater spiked with the water-soluble fraction of heavy residual oil. Water samples and settling particles in the tanks were collected periodically and 38 PAH compounds were analyzed by gas chromatography-mass spectrometry (GC-MS). Low molecular weight (LMW) PAHs with less than three benzene rings disappeared rapidly, mostly within 2 days. On the other hand, high molecular weight (HMW) PAHs with more than four benzene rings remained in the water column for a longer time, up to 9 days. Also, significant portions (10-94%) of HMW PAHs settled to the bottom and were caught in the sediment trap. The addition of chemical dispersant accelerated dissolution and biodegradation of PAHs, especially HMW PAHs. The dispersant amplified the amounts of PAHs found in the water column. The amplification was the greater for the more hydrophobic PAHs, with an enrichment factor of up to six times. The increased PAHs resulting from dispersant use overwhelmed the normal degradation and, as a result, higher concentrations of PAHs were observed in water column throughout the experimental period. We conclude that the addition of the dispersant could increase the concentration of water column PAHs and thus increase the exposure and potential toxicity for organisms in the natural environment. By making more hydrocarbon material available to the water column, the application of dispersant reduced the settling of PAHs. For the tank with dispersant, only 6% of chrysene initially introduced was detected in the sediment trap whereas 70% was found in the trap in the tank without dispersant.  相似文献   

Livestock wastes as a source of estrogens and their effects on wildlife of Manko tidal flat,Okinawa   总被引：9，自引：0，他引：9  

Tashiro Y  Takemura A  Fujii H  Takahira K  Nakanishi Y 《Marine pollution bulletin》2003,47(1-6):143-147

The Manko tidal flat in the southern part of Okinawa Island is an important visiting and wintering area for migratory birds and was added to the Ramsar Convention Register of Wetlands in 1999. This area used to be an inlet extending to the inner part of Naha Port, but recent reclamation projects have restricted its connection to the East China Sea. As is typical in rural regions of subtropical islands, the inhabitants in the Manko basin raise livestock, especially pigs, without employing sufficient waste treatment methods. As sewage treatment works are considered to be one of the main sources of environmental estrogens in urban areas, the significance of livestock farming as a source of estrogens in rural area is examined in this study. In the present study, total estrogenic activities in water and sediment samples from the Manko tidal flat and its basin were measured using a recombinant yeast screen method. Estrogenic activities (equivalent to 17beta-estradiol, E2) were around 10 ng l(-1) in water samples and more than 10 microg kg(-1) in some sediment samples. In addition, the concentrations of estrone (E1) and E2 in water samples measured using LC/MS/MS indicated a high contribution of environmental estrogens from livestock wastes.  相似文献   

Simulating the carbon balance of a temperate larch forest under various meteorological conditions     

Motomu Toda  Masayuki Yokozawa  Akihiro Sumida  Tsutomu Watanabe  Toshihiko Hara 《Carbon balance and management》2007,2(1):6

Background  

Changes in the timing of phenological events may cause the annual carbon budget of deciduous forests to change. Therefore, one should take such events into account when evaluating the effects of global warming on deciduous forests. In this article, we report on the results of numerical experiments done with a model that includes a phenological module simulating the timing of bud burst and other phenological events and estimating maximum leaf area index.  相似文献