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11.
Roland Bibron Concèle Leger Jacques Tobailem Yfji Yokoyama Hisao Mabuchi Noëlle Baillard 《Geochimica et cosmochimica acta》1974,38(2):197-205
]The activities of 18 radionuclides in 4 samples from the Saint-Séverin meteorite have been measured after chemical separation. The results show that the DI sample from the D piece has been less irradiated than the samples B2, B3 and B4 from the B piece. This is based on activities of isotopes produced both by spallation as 26Al, 53Mn, 54Mn, 55Fe, 57Co and by thermal neutron capture as 59Ni and 60Co.Comparison of experimental values to calculated production rates suggests that the D piece was connected to the main body of the meteorite by a small surface, and that the DI sample in this piece was opposite to the main body of the meteorite. 相似文献
12.
Takeo Hama Shoko Kawashima Koichi Shimotori Yuhi Satoh Yuko Omori Shigeki Wada Taiki Adachi Shun Hasegawa Takashi Midorikawa Masao Ishii Shu Saito Daisuke Sasano Hiroko Endo Tsuyoshi Nakayama Isao Inouye 《Journal of Oceanography》2012,68(1):183-194
The effect of ocean acidification, caused by the increase in pCO2 in seawater, on phytoplankton population and on related organic nitrogen production was experimentally examined by use of a natural coastal microbial population. pCO2 and pH were controlled by aeration with air in which pCO2 was at the current level (control), for which ambient air was used, and with air in which pCO2 was ??800?? and ??1200?? ppm, in 500-L culture vessels. The experiment was continued for 15?days after addition of the inorganic nutrients such as nitrate, phosphate, and silicate. During most of the experimental period, a minor increase in phytoplankton biomass was noted, probably because of low irradiance, an increase in phytoplankton biomass was observed at the end of the experiment. Flow cytometric and microscopic observations revealed that this increase was because of Chrysochromulina sp. (Haptophyceae). The growth of Chrysochromulina sp. was most obvious in the control vessel, and tended to be obscured by increasing pCO2 (decrease in pH), indicating the possibility that ocean acidification inhibits the growth of specific phytoplankton groups, for example Chrysochromulina sp. Production of particulate organic nitrogen (PON), determined by the 15N tracer method, also diminished under acidified conditions compared with that at the current level. 相似文献
13.
José H.A. Sobral Vivian M. de Castilho M.A. Abdu Hisao Takahashi I. Paulino Ulisses A.C. Gasparelo Daniela C.S. Arruda Matheus Mascarenhas C.J. Zamlutti C.M. Denardini Daiki Koga A.F. de Medeiros R.A. Buriti 《Journal of Atmospheric and Solar》2011,73(11-12):1520-1528
In an effort to better understand the dynamics of westward velocities of the nocturnal F-region plasma, the climatology of the westward traveling plasma bubbles – WTB – occurring during quiettime is studied here. The climatology of the WTB is analyzed here based on airglow images obtained during 14 quiet days between 2001 and 2006 at the Brazilian station São João do Cariri (Geographic 7.45°S, 36.5°W, dip ~20°S). The frequency of occurrence of the WTB maximizes in the descending phase of the solar cycle. The WTB velocities ranged between ~20 and 40 ms?1. The frequency of occurrence had a peak value of only 3.65% at 2345 LT. The maximum occurrence of the WTB was in July–September. No WTB have been observed from November until April in all years 2001–2006. We show for the first time theoretically that the WTB dominant forcing mechanisms during geomagnetically quiet days are westward thermospheric winds. 相似文献
14.
Diane E. Moore David A. Lockner Hisao Ito Riuji Ikeda Hidemi Tanaka Kentaro Omura 《Pure and Applied Geophysics》2009,166(10-11):1669-1691
Samples of damage-zone granodiorite and fault core from two drillholes into the active, strike-slip Nojima fault zone display microstructures and alteration features that explain their measured present-day strengths and permeabilities and provide insight on the evolution of these properties in the fault zone. The least deformed damage-zone rocks contain two sets of nearly perpendicular (60–90° angles), roughly vertical fractures that are concentrated in quartz-rich areas, with one set typically dominating over the other. With increasing intensity of deformation, which corresponds generally to increasing proximity to the core, zones of heavily fragmented rock, termed microbreccia zones, develop between prominent fractures of both sets. Granodiorite adjoining intersecting microbreccia zones in the active fault strands has been repeatedly fractured and locally brecciated, accompanied by the generation of millimeter-scale voids that are partly filled with secondary minerals. Minor shear bands overprint some of the heavily deformed areas, and small-scale shear zones form from the pairing of closely spaced shear bands. Strength and permeability measurements were made on core collected from the fault within a year after a major (Kobe) earthquake. Measured strengths of the samples decrease regularly with increasing fracturing and fragmentation, such that the gouge of the fault core and completely brecciated samples from the damage zone are the weakest. Permeability increases with increasing disruption, generally reaching a peak in heavily fractured but still more or less cohesive rock at the scale of the laboratory samples. Complete loss of cohesion, as in the gouge or the interiors of large microbreccia zones, is accompanied by a reduction of permeability by 1-2 orders of magnitude below the peak values. The core samples show abundant evidence of hydrothermal alteration and mineral precipitation. Permeability is thus expected to decrease and strength to increase somewhat in active fault strands between earthquakes, as mineral deposits progressively seal fractures and fill pore spaces. 相似文献
15.
Submillimeter Scale Variation of Oxygen Isotope of Vein Quartz at the Hishikari Deposit, Japan 总被引:2,自引:1,他引:1
Abstract: The physical and chemical mechanism of gold precipitation in the typical low-sulfidation epithermal gold deposit at the Hishikari mine was quantified by submillimeter scale oxygen isotope analyses of vein quartz. In situ CO2 laser-ablated fluorination was used to measure temporal δ18 O excursions. The calculated oxygen isotopic compositions of the ore-forming fluid indicate a dynamic process of epithermal vein formation. Intermittent opening of the vein allowed introduction of metal-bearing deep fluid to the epithermal system, and associated boiling and subsequent mixing with meteoric water caused precipitation of precious metals. 相似文献
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17.
If knowledge of our theories on the directivity of tsunamis had received worldwide attention, the following operations could have been carried out internationally just after the large earthquake of 19 September 1985 which occurred near Acapulco, Mexico. Having found the great circle, “line S” which is perpendicular to the coast around Acapulco, we could have calculated the angles between line S and line A and between line S and line D, where line A and line D are the great circle connecting Acapulco and Auckland, New Zealand and that connecting Acapulco and Duke of York Island (Chile), respectively. The resultant angles are 30?43′ and 41?49′(>68?48′/2), we could thereafter neglect the eastern half of the offshore energy flux. When we assume that the speed of trans-Pacific tsunami is 400 knots, the probability that the actual tsunami will come earlier than the calculated arrival time proves to be $$\frac{1}{{\sqrt {2\pi } }}\int_{ - {\text{ }}\infty }^{ - {\text{ }}0.689} {e^{ - t^{{2 \mathord{\left/ {\vphantom {2 2}} \right. \kern-\nulldelimiterspace} 2}} } dt = 0.2454} $$ Contact with New Zealand prior to the forecasted arrival time was essential, but the tsunami attention for the Japanese coast was unnecessary. Without such application of our directivity theories, frequent fruitless warnings will be issued for future trans-Pacific tsunamis. Quick improvements in warning procedures are required. 相似文献
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19.
Satoh?ToshimiEmail author Hiroshi?Kawase Tomotaka?Iwata Sadanori?Higashi Sato?Toshiaki Huey-Chu?Huang 《Journal of Seismology》2004,8(4):545-558
The 1999 Chi-Chi, Taiwan earthquake, MW = 7.6, caused severe damage in the near-fault region of the earthquake. In order to evaluate site effects in the near-field strong motions we estimate S-wave velocity structures of sediments at four sites using array records of microtremors. We also recalculated S-wave velocity structures at other four sites previously reported. To show the validity of the estimated S-wave velocity structures we separate empirical site responses from aftershock records using the generalized inversion method and show the agreement between empirical and theoretical site responses. We also show an observed fact that suggests soil nonlinearity during the Chi-Chi earthquake by comparing horizontal-to-vertical spectral ratios (HVRs) for main shock records with HVRs for aftershock records. Then we calculate one-dimensional equivalent-linear site responses using the estimated S-wave velocity structures and the main shock records observed on the surface. It is found that site amplification due to thick (about 6 km) sediments is one of the important factors for explaining the long-period velocity pulses of about 5 to 10 sec observed at sites in the footwall during the Chi-Chi earthquake. It is also found that the theoretical site responses of shallow soft sediments at sites that sustained severe damage in the hanging wall shows significant amplification around 1 sec. As the amplitude of velocity pulses with period around 1 sec is most critical in causing damage to ordinary buildings of moderate heights, our results suggest that the 1-sec period velocity pulses, amplified by the site response of shallow sediments should contribute to the severe damage during the Chi-Chi earthquake. 相似文献
20.
We delineate shallow structures of the Mozumi–Sukenobu fault, central Japan, using fault zone waves generated by near-surface explosions and detected by a seismometer array. Two explosive sources, S1 and S2, were placed at a distance of about 2 km from the array, and the other two, S3 and S4, were at a distance of about 4 km. Fault zone head waves and fault zone trapped waves following direct P wave arrivals were clearly identified in the seismograms recorded by a linear seismometer array deployed across the fault in a research tunnel at a depth of 300 m. Synthetic waveforms generated by a 3-D finite-difference (3-D FD) method were compared with observed fault zone waves up to 25 Hz. The best fitting model indicates a 200-m-wide low-velocity zone extending at least to shot site S1 located 2 km east of the seismic array with a 20% decrease in the P wave velocity relative to the wall rock. The width of the low-velocity zone is consistent with the fault zone defined by direct geological observation in the research tunnel. However, the low-velocity zone should disappear just to the east of the site S1 to explain the observed fault zone waves for shot S3 and S4 located 4 km east of the seismometer array. Yet the observation and the simulation show notable trapped wave excitation even though shots S3 and S4 are outside the fault zone. These results indicate that (1) the effective waveguide for seismic waves along the fault does not exist east of source site S1 although the surface traces of the fault are observed in this region, and (2) considerable trapped waves can be excited by sources well outside the fault zone. These results highlight the along-strike variability in fault zone structure. 相似文献