Semi-brittle behavior of wet olivine aggregates: the role of aqueous fluid in faulting at upper mantle pressures     

Tomohiro?OhuchiEmail author  Xinglin?Lei  Yuji?Higo  Yoshinori?Tange  Takeshi?Sakai  Kiyoshi?Fujino 《Contributions to Mineralogy and Petrology》2018,173(10):88

The role of aqueous fluid in fracturing in subducting slabs was investigated through a series of deformation experiments on dunite that was undersaturated (i.e., fluid-free) or saturated with water (i.e., aqueous-fluid bearing) at pressures of 1.0–1.8 GPa and temperatures of 670–1250 K, corresponding to the conditions of the shallower regions of the double seismic zone in slabs. In situ X-ray diffraction, radiography, and acoustic emissions (AEs) monitoring demonstrated that semi-brittle flow associated with AEs was dominant and the creep/failure strength of dunite was insensitive to the dissolved water content in olivine. In contrast, aqueous fluid drastically decreased the creep/failure strength of dunite (up to ~?1 GPa of weakening) over a wide range of temperatures in the semi-brittle regime. Weakening of the dunite by the aqueous fluid resulted in the reduction of the number of AE events (i.e., suppression of microcracking) and shortening of time to failure. The AE hypocenters were located at the margin of the deforming sample while the interior of the faulted sample was aseismic (i.e., aseismic semi-brittle flow) under water-saturated conditions. A faulting (slip rate of ~?10^?3 to 10^?4 s^?1) associated with a large drop of stress (Δσ?~?0.5 to 1 GPa) and/or pressure (ΔP?~?0.5 GPa) was dominant in fluid-free dunite, while a slow faulting (slip rate?<?8?×?10^?5 s^?1) without any stress/pressure drop was common in water-saturated dunite. Aseismic semi-brittle flow may mimic silent ductile flow under water-saturated conditions in subducting slabs.  相似文献   

Reconstructions of annual discharge and equilibrium line altitude of glaciers at Qilian Shan,northwest China,from 1978 to 2002     

Akiko Sakai  Koji Fujita  Chiyuki Narama  Jumpei Kubota  Masayoshi Nakawo  Tandong Yao 《水文研究》2010,24(19):2798-2806

Discharge was calculated from a mountainous area, including discharge from glaciers, in the Qilian Shan (Qilian Mountains) of northwest China. The studied Yingluoxia basin is 9983 km² in area, with glaciers making up 0·3% of the basin. The calculation method was based on the heat balance, requiring only daily temperature and precipitation. Calculated annual discharge from the basin corresponded well with the observed data. Calculated annual discharge from glaciers was 3·6% of the total discharge from the basin. The temporal trend of the calculated equilibrium line altitude (ELA) at the July 1st Glacier (western side of the Yingluoxia basin) was similar to that of the observed ELA. The calculated annual mass balance of glaciers within the Yingluoxia basin has a larger negative value than the other glaciers in China, as the ratio of accumulation area to the total glacier area in the Yingluoxia basin is much lower than in neighbouring basins to the west. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

Effects of dust abundance on the far-infrared colours of blue compact dwarf galaxies     

Hiroyuki Hirashita  Tomohiro T. Ichikawa 《Monthly notices of the Royal Astronomical Society》2009,396(1):500-510

We investigate the far-infrared (FIR) properties of a sample of blue compact dwarf galaxies (BCDs) observed by AKARI . By utilizing the data at wavelengths of  λ= 65  , 90 and 140 μm, we find that the FIR colours of the BCDs are located at the natural high-temperature extension of those of the Milky Way and the Magellanic Clouds. This implies that the optical properties of dust in BCDs are similar to those in the Milky Way. Indeed, we explain the FIR colours by assuming the same grain optical properties, which may be appropriate for amorphous dust grains, and the same size distribution as those adopted for the Milky Way dust. Since both interstellar radiation field and dust optical depth affect the dust temperature, it is difficult to distinguish which of these two physical properties is responsible for the change of FIR colours. Then, in order to examine if the dust optical depth plays an important role in determining the dust temperature, we investigate the correlation between FIR colour (dust temperature) and dust-to-gas ratio. We find that the dust temperature tends to be high as the dust-to-gas ratio decreases but that this trend cannot be explained by the effect of dust optical depth. Rather, it indicates a correlation between dust-to-gas ratio and interstellar radiation field. Although the metallicity may also play a role in this correlation, we suggest that the dust optical depth could regulate the star formation activities, which govern the interstellar radiation field. We also mention the importance of submillimetre data in tracing the emission from highly shielded low-temperature dust.  相似文献   

Variation of precipitation δ¹⁸O in Langtang Valley Himalayas   总被引：1，自引：0，他引：1  

Xinping Zhang  Nakawo Masayoshi  Koji Fujita  Tandong Yao  Jiankang Han 《中国科学D辑(英文版)》2001,44(9):769-778

The variation of the δ¹⁸O in precipitation and the relationship with precipitation amount at Kyangjin Base House and Yala Glacier Camp in Langtang Valley, Nepal Himalayas were analyzed. The variations of the δ¹⁸O with precipitation had great scatter, and the correlations between the δ¹⁸O and precipitation changed with time on the synoptic scale. On the seasonal scale, there was marked amount effect at Kyangjin Base House. However, the δ¹⁸O-precipitation gradient was smaller than that on the synoptic scale. Because of the maintenance of the basic equilibrium between stable isotopic compositions in atmospheric vapor and precipitation, the evaporation enrichment was light during the rainy season. Therefore, the variation of stable isotopic compositions in precipitation was independent on the sampling intervals. Simulations show that the rainfall in Langtang Valley was not the outcome of the initial condensation of ocean vapor that originated from low latitudes. The stable isotopic compositions in precipitation were greatly depleted due to the strong rainout of the vapor from oceans as the vapor was raised over the Himalayas.  相似文献   

Interannual variations of the occurrence of epipelagic fish in the diets of the seabirds breeding on Teuri Island, northern Hokkaido, Japan     

Tomohiro Deguchi  Yutaka Watanuki  Yasuaki Niizuma  Akifumi Nakata 《Progress in Oceanography》2004,61(2-4):267

The diets of breeding seabirds can be a good monitor of marine environmental changes. From 1984 to 2001 we monitored the diets of black-tailed gulls (Larus crassirostris) (“surface foragers”), rhinoceros auklets (Cerorhinca monocerata) (“epipelagic divers”), and Japanese cormorants (Phalacrocorax filamentotus) (“bottom divers”) that breed on Teuri Island at the northern boundary of the Tsushima Warm current in the Sea of Japan/East Sea. Between 1984 and 1987, both the gulls and the auklets foraged on the sardine (Sardinops melanostictus), but after 1992, they switched to the anchovy (Engraulis japonica). This change might reflect the collapse of the sardine stock in the late 1980s. In the 1990s, the year-to-year variations of the percentage of anchovy in the diets of the three seabird species showed similar trends: High in 1994 and 1998–2001; and low in 1992–1993 and 1995–1997. The estimated stock size of the anchovy population in the Tsushima Current area was positively correlated with the percentage of mass of anchovy in the seabirds’ diets. Thus, the short-term annual changes of the total anchovy availability, which might reflect SST or the volume transport of Tsushima Current, possibly affected the seabirds diets on this island.  相似文献   

Spatial structure within a dense bed of the brittle starOphiura sarsi (Ophiuroidea: Echinodermata) in the bathyal zone off otsuchi,Northeastern Japan     

Toshihiko Fujita  Suguru Ohta 《Journal of Oceanography》1989,45(5):289-300

Photographic observations of the brittle starOphiura sarsi were conducted at a depth of approximately 280 m in the Pacific Ocean off tsuchi, northeastern Japan. Bottom photographs showed that this ophiuroid occurred in high densities, uniformly covering the sea floor and that other megafauna was rare. The mean density and biomass of ophiuroids in the dense bed were estimated to be 373 m^–2 and 124 g m^–2, respectively. Ophiuroids comprised 99% of all megabenthic organisms in terms of number of individuals, and megafaunal assemblage of the dense bed showed very low species diversity.O. sarsi exhibited a regular spatial pattern avoiding contact with conspecific neighbors. This regular spatial pattern was disrupted by certain other organisms, around which halo-like, bare areas were observed. The size and shape of these halo-like areas varied and were apparently related to the body size and/or motility of the organisms. In the present observation areaO. sarsi covered 96% of the sea bottom, and the remaining 4% was occupied by other organisms and their halo-like bare areas.  相似文献   

A real-time observation network of ocean-bottom-seismometers deployed at the Sagami trough subduction zone,central Japan     

Eguchi  Takao  Fujinawa  Yukio  Fujita  Eisuke  Iwasaki  Sin-Iti  Watabe  Isao  Fujiwara  Hiroyuki 《Marine Geophysical Researches》1998,20(2):73-94

We installed a real-time operating regional observation network of Ocean-Bottom-Seismometers, connected to an electro-optical fiber communication cable, at the Sagami trough subduction zone, just south of the Tokyo metropolitan area, central Japan. The network, called ETMC, has six seismic observation sites at approximately 20 km spacing. In addition, there are three tsunami observation sites along the ETMC network to monitor the propagation process of tsunamis around the Sagami trough region.The on-line data from the ETMC has been improving the detection capability of smaller-magnitude earthquakes even at areas close to the margin of the trough. The ETMC data analyzing system, which has a function of real-time digital filtering for each seismic channel, can read the arrival times of P- and S-waves precisely, constraining well the automatic on-line hypocenter locations. The network has been providing useful information regarding the bending and downgoing process of the Philippine sea plate at the Sagami trough subduction zone.The pressure sensors of the installed network have a detection capability of tsunami wave trains with an amplitude of less than 1 cm. For example, the sensors recorded the full time history of tsunami wave trains, with mm order resolution, originating from a tsunami earthquake with 5.7 M_W and the tsunami magnitude of 7.5 occurred near Tori Shima (Tori Is.) of the Izu-Bonin Is. arc on September 4, 1996. The maximum amplitude of the tsunami signals on the trough-floor was approximately 1 cm (P-P), in contrast with approximately 20 cm (0-P) at a coastal site on Izu-Oshima, near the trough. Also, the pressure sensors observed tsunamis due to a large tsunami earthquake (7.1 M_W) at the northern New Guinea, on July 17, 1998.  相似文献   

Ammonium input to the sea via large sewage outfalls-Part 2: Effects of ammonium on growth and photosynthesis of southern California phytoplankton cultures     

W. H. Thomas  J. Hastings  M. Fujita 《Marine environmental research》1980,3(4):291-296

Cultures of six marine phytoplankton were grown at ammonium concentrations ranging up to 200 μg-atom NH₄---N litre⁻¹. Only the growth of dinoflagellates, Gymnodinium splendens and Gonyaulax polyedra was inhibited at the two highest concentrations used. In 3-h photosynthetic ¹⁴CO₂ uptake experiments, only Gymnodinium was inhibited at concentrations of NH₄---N greater than 100 μg-atom litre⁻¹. We conclude that the increased ammonium concentrations found near Southern California sewage outfalls would not be inhibiting to phytoplankton in the vicinity of such outfalls.  相似文献   

Magma intrusion and discharge process at the initial stage of the 2000 activity of Miyakejima, Central Japan, inferred from tilt and GPS data   总被引：2，自引：0，他引：2  

Hideki Ueda  Eisuke Fujita  Motoo Ukawa  Eiji Yamamoto  Meilano Irwan  Fumiaki Kimata 《Geophysical Journal International》2005,161(3):891-906

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冬克玛底冰川和煤矿冰川的物质平衡（1992／1993年）   总被引：2，自引：7，他引：2  

蒲健辰  濑古胜基 《冰川冻土》1995,17(2):138-143

对青藏高原唐古拉山大、小冬克玛底冰川和昆仑山煤矿冰川的同观测研究表明，１９９２／１９９３年冰川的物质平衡为正平衡，其平衡值唐古拉山冰川大于昆仑山冰川。冰川物质过程存在四个阶段，即低水平维持阶段，强积累弱消隔阶段，强消隔阶段和较强积累弱消隔阶段，空间上反映出随海拔升高波动增大的趋势。  相似文献