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481.
Takashi Ninomiya Shoichi Shimoyama Koichiro Watanabe Kenji Horie Daniel J. Dunkley Kazuyuki Shiraishi 《Island Arc》2014,23(3):206-220
The Taishu Group, a marine formation with a thickness of >5400 m, crops out on Tsushima Island, located in the southwestern Japan Sea. The group, which is generally regarded as early Eocene to early Miocene in age, provides important information about the tectonic setting of the Japan Sea. In this study, we present new SHRIMP U–Pb dates for igneous zircons from the Kunehama Tuff, which is in the basal part of the Taishu Group, and the Oobaura Tuff, which is in the uppermost part of the group. Results show that the Taishu Group was deposited rapidly, during the short interval of 17.9–15.9 Ma (early–middle Miocene), and is equivalent to other early–middle Miocene strata found in the Japan Sea region. Our results provide new constraints on the geological history of the Japan Sea and its islands. 相似文献
482.
Eleazar Padrón Pedro A. Hernández Nemesio M. Pérez Theofilos Toulkeridis Gladys Melián José Barrancos Giorgio Virgili Hirochika Sumino Kenji Notsu 《Bulletin of Volcanology》2012,74(6):1509-1519
Measurements of visible and diffuse gas emission were conducted in 2006 at the summit of Sierra Negra volcano, Galapagos, with the aim to better characterize degassing after the 2005 eruption. A total SO2 emission of 11?±?2?t day?1 was derived from miniature differential optical absorption spectrometer (mini-DOAS) ground-based measurements of the plume emanating from the Mini Azufral fumarolic area, the most important site of visible degassing at Sierra Negra volcano. Using a portable multigas system, the H2S/SO2, CO2/SO2, and H2O/SO2 molar ratios in the Mina Azufral plume emissions were found to be 0.41, 52.2, and 867.9, respectively. The corresponding H2O, CO2, and H2S emission rates were 562, 394, and 3?t day?1, respectively. The total output of diffuse CO2 emissions from the summit of Sierra Negra volcano was 990?±?85?t day?1, with 605?t day?1 being released by a deep source. The diffuse-to-plume CO2 emission ratio was about 1.5. Mina Azufral fumaroles released gasses containing 73.6?mol% of H2O; the main noncondensable components amounted to 97.4?mol% CO2, 1.5?mol% SO2, 0.6?mol% H2S, and 0.35?mol%?N2. The higher H2S/SO2 ratio values found in 2006 as compared to those reported before the 2005 eruption reveal a significant hydrothermal contribution to the fumarolic emissions. 3He/4He ratios measured at Mina Azufral fumarolic discharges showed values of 17.88?±?0.25?R A , indicating a mid-ocean ridge basalts (MORB) and a Galapagos plume contribution of 53 and 47?%, respectively. 相似文献
483.
The phenomenon of aftershocks is studied in view of science of complexity. In particular, three different concepts are examined:
(i) the complex-network representation of seismicity, (ii) the event-event correlations, and (iii) the effects of long-range
memory. Regarding (i), it is shown that the clustering coefficient of the complex earthquake network exhibits a peculiar behavior
at and after main shocks. Regarding (ii), it is found that aftershocks experience aging, and the associated scaling holds.
And regarding (iii), the scaling relation to be satisfied by a class of singular Markovian processes is violated, implying
the existence of the long-range memory in processes of aftershocks. 相似文献
484.
485.
486.
Contribution of CO2 and H2S emitted to the atmosphere by plume and diffuse degassing from volcanoes: the Etna volcano case study 总被引:1,自引:0,他引:1
487.
Vertical plant area density profiles of wheat (Triticum aestivum L.) canopy at different growth stages (tillering, stem elongation, flowering, and ripening stages) were estimated using high-resolution portable scanning lidar based on the voxel-based canopy profiling method. The canopy was scanned three-dimensionally by laser beams emitted from several measuring points surrounding the canopy. At the ripening stage, the central azimuth angle was inclined about 23° to the row direction to avoid obstruction of the beam into the lower canopy by the upper part. Plant area density profiles were estimated, with root mean square errors of 0.28–0.79 m2 m?3 at each growth stage and of 0.45 m2 m?3 across all growth stages. Plant area index was also estimated, with absolute errors of 4.7%–7.7% at each growth stage and of 6.1% across all growth stages. Based on lidar-derived plant area density, the area of each type of organ (stem, leaves, ears) per unit ground area was related to the actual dry weight of each organ type, and regression equations were obtained. The standard errors of the equations were 4.1 g m?2 for ears and 26.6 g m?2 for stems and leaves. Based on these equations, the estimated total dry weight was from 63.3 to 279.4 g m?2 for ears and from 35.8 to 375.3 g m?2 for stems and leaves across the growth stages. Based on the estimated dry weight at ripening and the ratio of carbon to dry weight in wheat plants, the carbon stocks were 76.3 g C m?2 for grain, 225.0 g C m?2 for aboveground residue, and 301.3 g C m?2 for all aboveground organs. 相似文献
488.
Food sources of the pearl oyster in coastal ecosystems of Japan: Evidence from diet and stable isotope analysis 总被引:1,自引:0,他引:1
Kayoko Fukumori Misa Oi Hideyuki Doi Noboru Okuda Hitomi Yamaguchi Michinobu Kuwae Hitoshi Miyasaka Kenji Yoshino Yoshitsugu Koizumi Koji Omori Hidetaka Takeoka 《Estuarine, Coastal and Shelf Science》2008
We estimated the composition of two food sources for the cultured pearl oyster Pinctada fucata martensii using stable isotopes and stomach content analysis in the coastal areas of the Uwa Sea, Japan. The δ13C values of oysters (−17.5 to −16.8‰) were intermediate between that of particulate organic matter (POM, −20.2 to −19.1‰) and attached microalgae on pearl cages (−13.0‰). An isotope mixing model suggested that oysters were consuming 78% POM (mainly phytoplankton) and 22% attached microalgae. The attached microalgal composition of the stomach content showed a strong resemblance to the composition of that estimated through the isotope mixing model, suggesting preferential utilization of specific components is unlikely in this species. These results indicate that P. fucata martensii feed on a mixture of phytoplankton and attached microalgae, and that the attached microalgae on pearl cages can serve as an important additional food source. 相似文献
489.
Akihiro Iwase Kazuhiko Sakai Atsushi Suzuki Robert van Woesik 《Estuarine, Coastal and Shelf Science》2008,77(4):672-678
We tested the hypothesis that foliose plates of Echinopora lamellosa (Esper, 1795) adjust their primary growth direction (or slope from the horizontal) when irradiance (light) is limiting. This hypothesis was tested at a coral-reef locality that is shaded daily by steep adjacent hills, restricting direct light to only a few hours each day (Iwayama Bay, Palau). The angle at which colonies received maximum light was measured using acetate film, and was compared with modeled estimates (using a simple global-light model). We show strong relationships between light and primary-colony gradients; with the foliose plates acting as parabolic antennae, predictably adjusting their primary gradients to optimize light capture. 相似文献
490.
Iron, manganese and aluminum in upper waters of the western South Pacific Ocean and its adjacent seas 总被引:1,自引:0,他引:1
Hajime Obata Kiminori Shitashima Kenji Isshiki Eiichiro Nakayama 《Journal of Oceanography》2008,64(2):233-245
Total dissolvable iron, manganese and aluminum distributions in upper waters were determined in the western South Pacific,
Solomon Sea, Coral Sea, and Tasman Sea. In these oceanic regions, the surface aluminum distributions well reflect the atmospheric
deposition pattern of mineral dust in the western South Pacific reported previously. Surface manganese distributions derive
mainly from lateral transportation from the coastal sediments of western tropical islands. Compared to Mn and Al, the Fe distributions
reflect the nutrient cycle in upper waters. Iron limitation over the vast South Pacific, as revealed by physiological features
of phytoplankton, seems to be caused by low atmospheric dust deposition and low Fe:N ratios in deep waters. In the western
South Pacific, with its unique geographic and oceanographic settings, the local sources of trace metals might considerably
affect their biogeochemical cycles. 相似文献