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71.
Climate Dynamics - Rain-on-Snow (ROS) events can cause severe snowmelt hazards such as river flooding, avalanches, and landslides that have significant impacts on various sectors. The influence of... 相似文献
72.
We performed three-dimensional (3-D) finite difference simulations of long-period ground motions (2–10 s) in the Kanto basin using the Japan Seismic Hazard Information Station (J-SHIS 2009), Yamada and Yamanaka (Exploration Geophysics 65(3):139–150, 2012) (YY), and Head Quarter for Earthquake Research Promotion (HERP 2012) velocity models for two intermediate depth (68–80 km) moderate earthquakes (Mw 5.8–5.9), which occurred beneath the Kanto basin. The models primarily differ in the basic data set used in the construction of the velocity models. The J-SHIS and HERP models are the results of integration of mainly geological, geophysical, and earthquake data. On the other hand, the YY model is oriented towards the microtremor-array-observation data. We obtained a goodness of fit between the observed and synthetic data based on three parameters, peak ground velocities (PGVs), smoothed Fourier spectra (FFT), and cross-correlations, using an algorithm proposed by Olsen and Mayhew (Seism Res Lett 81:715–723, 2010). We found that the three models reproduced the PGVs and FFT satisfactorily at most sites. However, the models performed poorly in terms of cross-correlations especially at the basin edges. We found that the synthetics using the YY model overestimate the observed waveforms at several sites located in the areas having V s 0.3 km/s in the top layer; on the other hand, the J-SHIS and HERP models explain the waveforms better at the sites and perform similarly at most sites. We also found that the J-SHIS and HERP models consist of thick sediments beneath some sites, where the YY model is preferable. Thus, we have concluded that the models require revisions for the reliable prediction of long-period ground motions from future large earthquakes. 相似文献
73.
U–Pb ages of detrital zircons and white mica K–Ar ages are obtained from two psammitic schists from the western and eastern units of the Sanbagawa Metamorphic Belt located in the Sakuma–Tenryu area. The detrital zircons in the sample from the western unit (T1) show an age cluster around 95 Ma, and the youngest age in the detrital zircons is 94.0 ± 0.6 Ma. The detrital zircons in the sample from the eastern unit (T5) show a main age cluster in the Late Cretaceous with some older ages, and the youngest age in the detrital zircons is 72.8 ± 0.9 Ma. The youngest zircon ages restrict the older limit of the depositional ages of each sample. White mica K–Ar ages of T1 and T5 are 69.8 ± 1.5 Ma and 56.1 ± 1.2 Ma, respectively, which indicate the age of exhumation and restrict the younger limit on the depositional age of each sample. The results show that the western and eastern units were different in their depositional and exhumation ages, suggesting the episodic subduction and exhumation of the Sanbagawa Belt in the Sakuma–Tenryu area. These results also suggest simultaneous existence of subduction and exhumation paths of metamorphic rocks in the high‐P/T Sanbagawa Metamorphic Belt. 相似文献
74.
This paper presents the geochemical study of sediments along Ube, Suo-Oshima, and Kasado Bays in the Seto Inland Sea of Japan. We examined the distribution and abundances of 13 elements (As, Pb, Zn, Cu, Ni, Cr, Sr, Ca, Fe, Ti, P, Mn, and total S) in 40 coastal and river sediment samples, to evaluate the factors controlling their abundances, possible sources, and environmental implications. Average concentrations of As, Pb, Zn, Cu, Ni, and Cr at Ube were 12, 26, 86, 16, 43, and 92?mg/kg, 6, 25, 31, 8, 9, and 29?mg/kg at Kasado, and 5, 20, 28, 3, 5, and 18?mg/kg at Suo-Oshima, respectively. Average As, Pb, Zn, and Cr concentrations at Ube were comparable or enriched relative to those of the upper continental crust and Japan upper crust, whereas most major elements, Cu, and Ni were depleted at Kasado and Suo-Oshima. Enrichment factor values show low to moderate enrichment of Zn, Ni, and Cr, whereas As and Pb show significant contamination at some sites, suggesting contributions from anthropogenic sources. Anthropogenic contributions of most metals mainly originate from natural processes; however, As and Pb ranges of 73–79 and 66–81?%, respectively, confirm their anthropogenic contribution. Factor analysis and correlation matrices suggest that elevated metal concentrations at Ube, especially in samples located in the river basin, may be controlled by Fe–Mn oxy-hydroxides. Deposition of metals at Kasado and Suo-Oshima might be controlled by non-ferrous metal (i.e., aluminosilicates), sediment grain size, or source rock composition (granite and gneiss). 相似文献
75.
The spring diatom bloom characterizes the plankton and nutrient dynamics in the Oyashio region, the westernmost part of the subarctic Pacific. Previous studies have shown that NO3 was not depleted during the spring bloom, and an increase in the consumption ratio of Si(OH)4 to NO3 (ΔSi(OH)4:ΔNO3) was observed as the spring bloom progressed. The increase in ΔSi(OH)4:ΔNO3 has been suggested to be caused by growth stresses of diatoms, e.g. light limitation by self-shading. In the present study, incubation experiments of sea-surface water from the Oyashio region under saturated irradiance showed that NO3 was depleted first and ΔSi(OH)4:ΔNO3 was more or less constant until the NO3 depletion occurred. The increase in ΔSi(OH)4:ΔNO3 was observed after the NO3 depletion had occurred in contrast with the field observation. This result of the increase in ΔSi(OH)4:ΔNO3 under saturated irradiance after NO3 depletion suggests that the in situ increase in ΔSi(OH)4:ΔNO3 before the NO3 depletion might be caused by light limitation for diatoms. Responses to a reduction in irradiance were examined using diatom species isolated from the Oyashio region. Variable responses to a reduced irradiance were observed for cell specific C, N, Si and chlorophyll a (Chl) contents. However, the examined diatom species showed similar tendencies for increases in Si:C and Si:N and decreases in C:Chl ratios with the reduction in irradiance. We conclude that light limitation changes the uptake ratio of nutrients and the elemental composition of diatoms and that light limitation is one of the factors influencing the physiology of diatoms and nutrient dynamics in the Oyashio region during the spring bloom. 相似文献
76.
Sayaka Sogawa Hiroya Sugisaki Hiroaki Saito Yuji Okazaki Shinji Shimode Tomohiko Kikuchi 《Journal of Oceanography》2013,69(1):71-85
The relationship between euphausiid community structure and water region was studied during a 2-year seasonal survey in the northwestern (NW) Pacific Ocean. The euphausiid community structure and its associated species were analyzed from 38 micronekton samples collected during eight cruises. The euphausiid community structure and its distribution patterns clearly corresponded to physical oceanographic features in the Oyashio region, Oyashio–Kuroshio Mixed Water Region (OKMWR), and Kuroshio region. In contrast, community structure was unrelated to seasonality. The 19 species out of 40 identified in this area were grouped and named after their habitats. The six cold-water species were grouped into three regional types: two coastal Oyashio species, three Oyashio–OKMWR species, and one Oyashio–Kuroshio species. The four species dominating in the OKMWR were categorized into each specific types: Nematoscelis difficilis as OKMWR–Oyashio species, Euphausia gibboides as OKMWR species, Euphausia similis as OKMWR–Oyashio & OKMWR–Kuroshio species, and Euphausia recurva as OKMWR–Kuroshio species. The seven warm-water species were categorized as Kuroshio–OKMWR species or Kuroshio species. The other two species were categorized as cosmopolitan species. In particular, regarding the result in the OKMWR, our study suggest that (1) the OKMWR has high species diversity, and (2) the dominant species, such as Euphausia pacifica, N. difficilis, E. similis, and E. gibboides, are considered to be key species in the food webs in this region. 相似文献
77.
Naoki Kabeya Nick A. Chappell Wlodek Tych Akira Shimizu Shiho Asano Hiroaki Hagino 《水文科学杂志》2016,61(9):1716-1727
ABSTRACTA new method known as Unobserved Components–Dynamic Harmonic Regression (UC-DHR) was applied to a 39-year record of rainfall and streamflow for three sub-catchments of the Sarukawa Experimental Watershed in southwestern Japan. Some 25% of the timber was harvested from one of the sub-catchments in May–July 1982 and the objective was to quantify the magnitude of this effect relative to the effects of climate cycles (e.g. Southern Oscillation Index). The observed effects of inter-annual climate cycles (i.e. 0.89–1.36 mm/d) were seen to be comparable (i.e. 0.70–1.17 mm/d) to the effects of harvesting 25% of the standing timber. This result underlines the importance of always quantifying the effect of climate on streamflow response when harvesting impacts are studied.
Editor D. Koutsoyiannis; Associate editor T. Okruszko 相似文献
78.
HAYASHI Hiroaki 《资源与生态学报(英文版)》2014,5(4):395-397
<正>1 Characteristics of Kunisaki GIAS and aims of this research Kunisaki GIAHS in the Kunisaki peninsula and Usa area,Oita,Japan,is a system where forestry,agricultural production,and fisheries are sustained by the strong connection between Sawtooth Oak forest,multiple interlinked irriga tion ponds,and Seto Inland Sea(Vafadari 2013a;2013b;Hayashi 2013).This area receive around 1,500 mm of annual precipitation with a 相似文献
79.
Madurya Adikaram Amarasooriya Pitawala Hiroaki Ishiga Daham Jayawardhana 《Journal of the Geological Society of India》2017,89(1):71-76
Quaternary sediment deposits are well exposed along the eastern coastal margin of Sri Lanka. Systematic trace fossil studies along with sediment characteristics have been carried out for the first time to interpret the paleoenvironment that prevailed during Quaternary sedimentation in eastern Sri Lanka. The trace fossils Thalassinoides, Skolithos and Polykladichnus have been recognized about 5m above the present mean sea level. Features of the major trace fossil, Thalassinoides, indicate that it was formed by Thalassinidean shrimp Calianassa. Isolated, vertical to steeply inclined, cylindrical to sub cylindrical tubes with thin internal wall lining and inner wall striations of Skolithos and Polykladichnus show that they were formed by polychaetes. The typical characteristic of Polykladichnus isY-shaped branching with slight enlargement at junctions. Morphology and association of burrows as well as mineralogy, grain size and roundness of sediments indicate that the environment prevailed was marine soft grounds of the intertidal zone. Presence of preserved fine-scale features of burrows indicate that the bioturbated sandy tidal flat was suddenly exposed to the tropical environment due to sea level regression in Quaternary periods. Due to the microbial activities of wall linings, burrows were preserved and it was supported by other microbial activities that produced secondary iron bearing minerals that suffered subsequent oxidation. The bio-origination of red sediments of eastern coastal area of the present study can be used to interpret the debatable origin of the red beds found in northwestern and southeastern coastal areas of the island. 相似文献
80.
Madurya Adikaram Amarasooriya Pitawala Hiroaki Ishiga Daham Jayawardana 《Environmental Earth Sciences》2017,76(24):817
The concentrations of Br and I in marine sediments have been used to categorize the sedimentary environments of different coastal regions of the world with respect to organic matter contents. The present study uses the concentrations of Br, I and P2O5 of different marine settings as a new proxy to interpret the depositional environments. A total of 150 coastal lagoon sediment samples (suspended sediments, surface sediments and sediment cores) were analyzed for Br, I and P2O5 concentrations by X-ray fluorescence spectrometry. They were compared with the Br, I and P2O5 concentrations of the 2004 Indian Ocean tsunami sediments. Sediments from various sources are separately clustered in I–Br plot and a trivial negative correlation is found for the whole plot. A similar correlation pattern exists in the I–P2O5 diagram. This correlation is explained by the distribution of marine plants (higher and lower) in different sedimentary environments of the coastal profile. Therefore, the concentration of I and its relation to P2O5 can be used as a tool to identify sediment depositional environments in marine settings. 相似文献