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131.
Geochemical characteristics of deposits from the 2011 Tohoku‐oki tsunami at Hasunuma,Kujukuri coastal plain,Japan
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Tetsuya Shinozaki Yuki Sawai Junko Hara Minoru Ikehara Dan Matsumoto Koichiro Tanigawa 《Island Arc》2016,25(5):350-368
We examined the geochemical characteristics and temporal changes of deposits associated with the 2011 Tohoku‐oki tsunami. Stable carbon isotope ratios, biomarkers, and water‐leachable ions were measured in a sandy tsunami deposit and associated soils sampled at Hasunuma, Kujukuri coastal plain, Japan, in 2011 and 2014. At this site, the 2011 tsunami formed a 10–30 cm ‐thick layer of very fine to medium sand. The tsunami deposit was organic‐poor, and no samples contained any detectable biomarkers of either terrigenous or marine origin. In the underlying soil, we identified hydrocarbons and sterols derived from terrestrial plants, but detected no biomarkers of marine origin. In the samples collected in 2011, concentrations of tsunami‐derived water‐leachable ions were highest in the soil immediately beneath the tsunami deposit and then decreased gradually with depth. Because of its finer texture and higher organic content, the soil has a higher water‐holding capacity than the sandy tsunami deposit. This distribution suggests that ions derived from the tsunami quickly penetrated the sand layer and became concentrated in the underlying soil. In the samples collected in 2014, concentrations of water‐leachable ions were very low in both soil and sand. We attribute the decrease in ion concentrations to post‐tsunami rainfall, seepage, and seasonal changes in groundwater level. Although water‐leachable ions derived from seawater were concentrated in the soil beneath the tsunami deposit following the tsunami inundation, they were not retained for more than a few years. To elucidate the behavior of geochemical characteristics associated with tsunamis, further research on organic‐rich muddy deposits (muddy tsunami deposits and soils beneath sandy tsunami deposits) as well as sandy tsunami deposits is required. 相似文献
132.
Hiroyuki R. Takahashi Eiji Asano Ryoji Matsumoto 《Monthly notices of the Royal Astronomical Society》2009,394(1):547-568
We obtained self-similar solutions of relativistically expanding magnetic loops taking into account the azimuthal magnetic fields. We neglect stellar rotation and assume axisymmetry and a purely radial flow. As the magnetic loops expand, the initial dipole magnetic field is stretched into the radial direction. When the expansion speed approaches the light speed, the displacement current reduces the toroidal current and modifies the distribution of the plasma lifted up from the central star. Since these self-similar solutions describe the free expansion of the magnetic loops, i.e. d v /d t = 0 , the equations of motion are similar to those of the static relativistic magnetohydrodynamics. This allows us to estimate the total energy stored in the magnetic loops by applying the virial theorem. This energy is comparable to that of the giant flares observed in magnetars. 相似文献
133.
Taro Nakai Akihiro Sumida Kazuho Matsumoto Ken’ichi Daikoku Shin’ichi Iida Hotaek Park Mie Miyahara Yuji Kodama Alexander V. Kononov Trofim C. Maximov Hironori Yabuki Toshihiko Hara Takeshi Ohta 《Boundary-Layer Meteorology》2008,128(3):423-443
We used an aerodynamic method to objectively determine a representative canopy height, using standard meteorological measurements.
The canopy height may change if the tree height is used to represent the actual canopy, but little work to date has focused
on creating a standard for determining the representative canopy height. Here we propose the ‘aerodynamic canopy height’ h
a as the most effective means of resolving the representative canopy height for all forests. We determined h
a by simple linear regression between zero-plane displacement d and roughness length z
0, without the need for stand inventory data. The applicability of h
a was confirmed in five different forests, including a forest with a complex canopy structure. Comparison with stand inventory
data showed that h
a was almost equivalent to the representative height of trees composing the crown surface if the forest had a simple structure,
or to the representative height of taller trees composing the upper canopy in forests with a complex canopy structure. The
linear relationship between d and z
0 was explained by assuming that the logarithmic wind profile above the canopy and the exponential wind profile within the
canopy were continuous and smooth at canopy height. This was supported by observations, which showed that h
a was essentially the same as the height defined by the inflection point of the vertical profile of wind speed. The applicability
of h
a was also verified using data from several previous studies. 相似文献
134.
Zhou Weijian Douglas J. Donahue Stephen C. Porter Timothy A. Jull Li Xiaoqiang Minze Stuiver An Zhisheng Eiji Matsumoto Dong Guangrong 《Quaternary Research》1996,46(3):219-229
High-resolution paleomonsoon proxy records from peat and eolian sand–paleosol sequences at the desert–loess transition zone in China denote a rapid oscillation from cold–dry conditions (11,200–10,60014C yr B.P.) to cool–humid conditions (10,600–10,20014C yr B.P.), followed by a return to cold–dry climate (10,200–10,00014C yr B.P.). Variations in precipitation proxies suggest that significant climatic variability occurred in monsoonal eastern Asia during the Younger Dryas interval. Late-glacial climate in the Chinese desert–loess belt that lies downwind from Europe was strongly influenced by cold air from high latitudes and from the North Atlantic via the westerlies. The inferred precipitation variations were likely caused by variations in the strength of the Siberian high, which influenced the pressure gradient between land and ocean and therefore influenced the position of the East Asian monsoon front. 相似文献
135.
Use of a resistivity cone for detecting contaminated soil layers 总被引:11,自引:0,他引:11
A cone-penetration technique was developed to detect contaminated soil layers with electrolytes and NAPLs. In this study, laboratory and field experiments were performed to apply the technique. In the laboratory, the change in resistivity was quantitatively examined by adding salt or oil to soil samples. The results showed that the resistivity measurement was varied with an order of ppm for the electrolyte concentration in soil. It was found that the resistivity of sand increased with increasing oil concentration. The effect of oil content was stronger for lower water content of sand.
The results obtained from field experiments showed that the resistivity cone can be used for detecting the contaminated layer in soils whose background values are known. Particularly, the instrument can be used effectively for examining the effects of remediation, by measuring the resistivity of the ground before and after remediation, unless the soil fabric changes significantly during remediation procedures. 相似文献
136.
137.
Sediment core was collected from Tokyo Bay. The surface enrichment of heavy metals due to human activities is recognized in the sediment. Partitioning of Cu, Zn, Fe and Mn into sulfide, carbonate, organic and silicate fractions has been determined with selective chemical leaching techniques for 210Pb-dated sediment core samples. The heavy metal contents of silicate fractions without exchangeable sites are almost constant against depth in sediment core. However, the Cu, Zn and Mn contents of sulfide, carbonate and organic fractions vary with depth. Most Cu and Zn in the polluted sediment layer are associated with the iron sulfide fraction. 相似文献
138.
Eiji Matsumoto 《Geochimica et cosmochimica acta》1975,39(2):205-212
234Th produced from 238U within sea water was found to be in radioactive disequilibrium with respect to its progenitor nuclide 238U in the surface layer of the ocean. The median value for activity ratio is 0.80 in the upper 200 m layer. A box-model calculation gives a removal residence time of thorium of about 0.38 yr. This suggests that 234Th is scavenged from the surface layer by the uptake of thorium by biota. 相似文献
139.
Detection and Evaluation of Gas Hydrates in the Eastern Nankai Trough by Geochemical and Geophysical Methods 总被引:2,自引:0,他引:2
Abstract: Interstitial waters extracted from the sediment cores from the exploration wells, “BH‐1” and “MITI Nankai Trough”, drilled ~60 km off Omaezaki Peninsula in the eastern Nankai Trough, were analyzed for the chloride and sulfate concentrations to examine the depth profiles and occurrence of subsurface gas hydrates. Cored intervals from the seafloor to 310 mbsf were divided into Unit 1 (~70 mbsf, predominated by mud), Unit 2 (70–150 mbsf, mud with thin ash beds), Unit 3 (150–250+ mbsf, mud with thin ash and sand), and Unit 4 (275–310 mbsf, predominated by mud). The baseline level for Cl “concentrations was 540 mM, whereas low chloride anomalies (103 to 223 mM) were identified at around 207 mbsf (zone A), 234–240 mbsf (zone B), and 258–265 mbsf (zone C) in Unit 3. Gas hydrate saturation (Sh %) of sediment pores was calculated to be 60 % (zone A) to 80 % (zones B and C) in sands whereas only a few percent in clay and silt. The total amount of gas hydrates in hydrate‐bearing sands was estimated to be 8 to 10 m3 of solid gas hydrate per m2, or 1.48 km3 CH4 per 1 km2. High saturation zones (A, B and C) were consistent with anomaly zones recognized in sonic and resistivity logs. 2D and high‐resolution seismic studies revealed two BSRs in the study area. Strong BSRs (BSR‐1) at ~263 mbsf were correlated to the boundary between gas hydrate‐bearing sands (zone C) and the shallower low velocity zone, while the lower BSRs (BSR‐2) at~289 mbsf corresponded to the top of the deeper low velocity zone of the sonic log. Tectonic uplift of the study area is thought to have caused the upward migration of BGHS. That is, BSR‐1 corresponds to the new BGHS and BSR‐2 to the old BGHS. Relic gas hydrates and free gas may survive in the interval between BSR‐1 and BSR‐2, and below BSR‐2, respectively. Direct measurements of the formation temperature for the top 170 m interval yield a geothermal gradient of ~4.3d?C/ 100 m. Extrapolation of this gradient down to the base of gas hydrate stability yields a theoretical BGHS at~230 mbsf, surprisingly ~35 m shallower than the base of gas hydrate‐bearing sands (zone C) and BSR‐1. As with the double BSRs, another tectonic uplift may explain the BGHS at unreasonably shallow depths. Alternatively, linear extrapolation of the geothermal gradient down to the hydrate‐bearing zones may not be appropriate if the gradient changes below the depths that were measured. Recognition of double BSRs (263 and 289 mbsf) and probable new BGHS (~230 mbsf) in the exploration wells implies that the BGHS has gradually migrated upward. Tectonically induced processes are thought to have enhanced dense and massive accumulation of gas hydrate deposits through effective methane recycling and condensation. To test the hypothetical models for the accumulation of gas hydrates in Nankai accretionary prism, we strongly propose to measure the equilibrium temperatures for the entire depth range down to the free gas zone below predicted BGHS and to reconstruct the water depths and uplift history of hydrate‐bearing area. 相似文献
140.
Takane Matsumoto Renji Naruse Keiko Konya Satoru Yamaguchi Tomomi Yamada Yaroslav D. Muravyev 《Geografiska Annaler: Series A, Physical Geography》2004,86(2):181-190
The daily water balance for the drainage basin of Koryto Glacier, Kamchatka Peninsula, Russia, was calculated during the period from August to September 2000. The result shows that 14×106 m3 of meltwater and 2×106 m3 of rainwater entered the basin, while 26×106 m3 of water drained from the basin through proglacial streams. Thus, about ?9×106 m3 of water storage reduction occurred in the basin. Vertical displacements of the glacier surface showed that the volume change due to contraction of subglacial cavities was nearly 20% of the total storage change. The remaining fraction of water storage during the period is thought to be stored in englacial and supraglacial locations. The estimate of water balance components in the early ablation season in 2000 indicates that meltwater was already stored within the glacier before the spring, even during the previous year, and that the stored water drained through the ablation season. 相似文献