排序方式： 共有38条查询结果，搜索用时 15 毫秒
1.
Richard A. Staff Takeshi Nakagawa Gordon Schlolaut Michael H. Marshall Achim Brauer Henry F. Lamb Christopher Bronk Ramsey Charlotte L. Bryant Fiona Brock Hiroyuki Kitagawa Johannes van der Plicht Rebecca L. Payne Victoria C. Smith Darren F. Mark Alison Macleod Simon P. E. Blockley Jean‐Luc Schwenninger Pavel E. Tarasov Tsuyoshi Haraguchi Katsuya Gotanda Hitoshi Yonenobu Yusuke Yokoyama Suigetsu Project Members 《Boreas: An International Journal of Quaternary Research》2013,42(2):259-266
The varved sediment of Lake Suigetsu (central Japan) provides a valuable opportunity to obtain high‐resolution, multi‐proxy palaeoenvironmental data across the last glacial/interglacial cycle. In order to maximize the potential of this archive, a well‐constrained chronology is required. This paper outlines the multiple geochronological techniques being applied – namely varve counting, radiocarbon dating, tephrochronology (including argon–argon dating) and optically stimulated luminescence (OSL) – and the approaches by which these techniques are being integrated to form a single, coherent, robust chronology. Importantly, we also describe here the linkage of the floating Lake Suigetsu (SG06) varve chronology and the absolute (IntCal09 tree‐ring) time scale, as derived using radiocarbon data from the uppermost (non‐varved) portion of the core. This tie‐point, defined as a distinct (flood) marker horizon in SG06 (event layer B‐07–08 at 1397.4 cm composite depth), is thus derived to be 11 255 to 11 222 IntCal09 cal. years BP (68.2% probability range). 相似文献
2.
Application of Convergence Confinement Analysis to the study of preceding displacement of a squeezing rock tunnel 总被引：4，自引：0，他引：4
T. Kitagawa T. Kumeta T. Ichizyo S. Soga M. Sato M. Yasukawa 《Rock Mechanics and Rock Engineering》1991,24(1):31-51
Summary This paper deals with a study on the geomechanical behavior of the rock mass around the tunnel. The Convergence Confinement Analysis is one of the most appropriate way to estimate this behavior. Elasto-plastic models proposed by Hoek and Brown, Egger and Kastner were adopted in this study.Measurements of the preceding displacement were performed in a road tunnel in Japan, the geology of which is Neogene squeezing mudstone. The measured data was compared with the results of Convergence Confinement Analysis.The preceding displacement was about 40% against the upper bench face converged displacement and 17% against the final converged displacement. Meanwhile, it increased drastically in lower bench excavation step.Back analysis was also executed to calculate the extension of the plastic zone of the rock mass, which was half of that estimated by Convergence Confinement Analysis in upper bench excavation step. But, in lower bench excavation step, the results of the two analyses were very similar. The support pressure and support stiffness were also calculated. 相似文献
3.
We infer the groundwater-level anomalies associated with a hypothetical preslip prior to the anticipated M 8 Tokai earthquake,
and evaluate the detectability of the anomalies using data from seven groundwater wells. We evaluate the detectability of
the anomalies under the following assumptions: (1) an Mw 5.5–6.5 aseismic preslip event occurs at the plate boundary in and
around the hypothetical focal zone of the Tokai earthquake; (2) the total amount of the strain step at each observation associated
with the preslip can be calculated by tensile and shear faulting based on the dislocation model; (3) a normalized strain history
associated with the preslip is defined from the results of numerical simulations based on rate- and state-dependent friction
laws; and (4) the groundwater-level anomaly prior to the earthquake is proportional to the estimated history of the strain
change associated with the preslip. We investigate the detection time of the anomaly at seven wells given an Mw 5.5, 6.0,
or 6.5 aseismic preslip at one of the 272 grid points in and around the area of the hypothetical focal zone of the Tokai earthquake.
As a result, over the time interval between 1 and 48 hours prior to the hypothetical Tokai earthquake, we are able to detect
at each of the seven wells a hypothetical Mw 6.5 preslip at 10–86 of the 272 grid points, an Mw 6 preslip at 0–19 grid points,
and an Mw 5.5 preslip at 0–5 grid points. 相似文献
4.
Toshiyuki Masuzawa Nobuhiko Handa Hiroyuki Kitagawa Minoru Kusakabe 《Earth and Planetary Science Letters》1992,110(1-4):39-50
Two sandy sediment cores (Cores D227-120 and D380) were collected from inside a deep-sea giant clam (Calyptogena soyoae) community off Hatsushima Island, western Sagami Bay, central Japan (35°59.9′N, 139°13.6′E; 1160 m deep) and a muddy sediment core (Core D227-202) was obtained from outside the community by the submersibleShinkai 2000. The chloride concentration of the pore waters is constant vertically and sulfate reduction using sedimentary organic matter occurs in Core D227-202 (21 cm long). The chloride concentrations are lower by 7% at the 7.5–9 cm depth in Core D227-120 (9 cm long) and by 3% at the 11–12 cm depth in Core D380 (16 cm long) than those of the overlying bottom waters in the cores from inside of the community. Sulfate concentration decreases remarkably and dissolved inorganic carbon, alkalinity, ammonium-N, and hydrogen sulfide concentrations increase significantly with increasing depth in Core D380.δ34S values of sulfate ions increase from +20.5 to +35.3‰ andδ13C values of dissolved inorganic carbon decrease drastically from −7.0 to −45‰ with increasing depth from the top to the bottom of the core, although theδ13C values of the organic carbon of the sediments are−23.7 ± 0.9‰ in Core D380. These results indicate that sulfate reduction using methane is active within the sediments just beneath the living clams and that the hydrogen sulfide produced can be used by endosymbiotic sulfur oxidizing bacteria living in the gills ofC. soyoae in the community. 相似文献
5.
碱尘暴期间松嫩平原西部碱尘气溶胶的主要元素质量浓度排序为Na、Al、Fe、Ca、Mg、K、Ti、Ba、Zn,与当地盐碱化土壤的元素组成吻合,而与沙尘、城市气溶胶的元素组成有差别。风力对碱尘气溶胶元素组成有明显的影响,当风速在8.0~17.1 m/s时,元素组成的质量浓度排序为Na、Ca、Al、Fe、Mg、K、Ba、Ti、Zn。Na元素质量浓度的激增是碱尘暴元素组分的一大特征,明显富集元素为Na和B;相对于当地背景大气气溶胶的富集情况,Zn、Cu、Ba、B的富集因子值在碱尘暴期间明显降低;在各种天气情况下,B、Cu均具有较高的富集因子。碱尘中Ti元素的富集因子值均小于1,而Ca、Fe、K、Mg、Mn、Sr、V的富集因子值为1~4。两个采样点的Ca、Na、Al、Fe、Mg、Ti、Zn的富集因子近似,表明该区碱尘的主要元素具有特定的一致性;而B、Ba、Cu、V的富集因子相差较大,可以作为区分不同碱尘源的标志性元素。 相似文献
6.
Single-Column Model Intercomparison for a Stably Stratified Atmospheric Boundary Layer 总被引：2，自引：15，他引：2
J. Cuxart A. A. M. Holtslag R. J. Beare E. Bazile A. Beljaars A. Cheng L. Conangla M. Ek F. Freedman R. Hamdi A. Kerstein H. Kitagawa G. Lenderink D. Lewellen J. Mailhot T. Mauritsen V. Perov G. Schayes G-J. Steeneveld G. Svensson P. Taylor W. Weng S. Wunsch K-M. Xu 《Boundary-Layer Meteorology》2006,118(2):273-303
The parameterization of the stably stratified atmospheric boundary layer is a difficult issue, having a significant impact on medium-range weather forecasts and climate integrations. To pursue this further, a moderately stratified Arctic case is simulated by nineteen single-column turbulence schemes. Statistics from a large-eddy simulation intercomparison made for the same case by eleven different models are used as a guiding reference. The single-column parameterizations include research and operational schemes from major forecast and climate research centres. Results from first-order schemes, a large number of turbulence kinetic energy closures, and other models were used. There is a large spread in the results; in general, the operational schemes mix over a deeper layer than the research schemes, and the turbulence kinetic energy and other higher-order closures give results closer to the statistics obtained from the large-eddy simulations. The sensitivities of the schemes to the parameters of their turbulence closures are partially explored. 相似文献
7.
Seto Koji Katsuki Kota Tsujimoto Akira Kitagawa Junko Yamada Kazuyoshi Suzuki Yoshiaki 《Journal of Paleolimnology》2022,68(3):329-343
Journal of Paleolimnology - Sub-annual-scale environmental and ecosystem changes since the mid-18th century were reconstructed in a semi-closed lagoon, Lake Hiruga, located along the Sea of Japan... 相似文献
8.
Deep CTD Casts in the Challenger Deep,Mariana Trench 总被引：1，自引：0，他引：1
Keisuke?TairaEmail author Daigo?Yanagimoto Shoji?Kitagawa 《Journal of Oceanography》2005,61(3):447-454
On 1 December 1992, CTD (conductivity-temperature-depth profiler) casts were made at three stations in a north-south section of the Challenger Deep to examine temperature and salinity profiles. The station in the Challenger Deep was located at 11°22.78′ N and 142°34.95′ E, and the CTD cast was made down to 11197 db or 10877 m, 7 m above the bottom by reeling out titanium cable of 10980 m length. The southern station was located at 11° 14.19′ N and 142°34.79′ E, 16.1 km from the central station, where water depth is 9012 m. CTD was lowered to 7014 db or 6872 m. The northern station was located at 11°31.47′ N and 142° 35.30′ E, 15.9 km from the central station, and CTD was lowered to 8536 db or 8336 m, 10 m above the bottom. Below the thermocline, potential temperature decreased monotonously down to 7300–7500 db beyond a sill depth between 5500 m and 6000 m, or between 5597 db and 6112 db, of the trench. Potential temperature increased from 7500 db to the bottom at a constant rate of 0.9 m°C/1000 db. Salinity increased down to 6020–6320 db, and then stayed almost constant down to around 9000 db. From 9500 db to the bottom, salinity increased up to 34.703 psu at 11197 db. Potential density referred to 8000 db increased monotonously down to about 6200 db, and it was almost constant from 6500 db to 9500 db. Potential density increased from 9500 db in accordance with the salinity increase. Geostrophic flows were calculated from the CTD data at three stations. Below an adopted reference level of 3000 db, the flow was westward in the north of Challenger Deep and eastward in the south, which suggests a cyclonic circulation over the Challenger Deep. Sound speed in Challenger Deep was estimated from the CTD data, and a relation among readout depth of the sonic depth recorder, true depth, and pressure was examined. 相似文献
9.
Moshood Niyi Tijani Matthew Essien Nton Ryuji Kitagawa 《Comptes Rendus Geoscience》2010,342(2):136-150
This study presents the mineralogical, textural and geochemical characteristics of the regional Maastrichtian Ajali Sandstone in Anambra Basin, SE Nigeria. The intent is to highlight possible constraints on the chemical weathering conditions of the source materials on one hand, and to infer the provenance on the other hand. The investigation approach involved field studies and collection of samples from 12 different outcrop locations, followed by laboratory studies involving grain-size analysis (GSA), major and trace elements analyses using the X-ray fluorescence (XRF) method as well as thin section petrography. Field studies show that the sandstones are friable at all locations and range in color from white in freshly cut stone, to reddish brown on weathering. In addition, the sandstone units are cross-bedded and show graded bedding exemplified by fining upward sequence. Textural examination indicates that the sandstones range from fine to medium sands, constituting about 76 to 99% sand fraction, with graphic mean grain size of 0.23 to 0.53 mm. Standard deviation (sorting) ranges from 0.56 to 1.24 Ø and implies moderately well sorted sediments. Inferred from the textural indices, the depo-environmental discrimination of the Ajali Sandstone revealed a fluvial/river system-dominated sedimentary process. The sandstones are quartz arenite with quartz greater than 90% and less than 5% K-feldspar which indicate a predominant basement source as also revealed by the heavy mineral assemblages. In addition, major elemental oxides shows SiO2 content greater than 96% for the fresh Ajali Sandstone samples with extreme depletion of mobile oxides such as Na2O, CaO and the ferromagnesian minerals through weathering and sedimentary processes. Provenance and tectonic setting discrimination using geochemical data and compositional maturity revealed typical felsic igneous-dominated cratonic environment while inter-elemental ratios (such as Zr/Cr, Y/Ni, Th/Sc, La/Sc and La/Co) and ternary plots (e.g. Th–Sc–Zr; La-Th–Sc and Th-Co-Zr) reflect passive continental margin setting for the Ajali Sandstone. Consequently, the source area is constrained to the Precambrian basement rock units of Adamawa-Oban massif areas to the east of the Anambra Basin and the adjacent Abakaliki Anticlinorium. 相似文献
10.
G. Svensson A. A. M. Holtslag V. Kumar T. Mauritsen G. J. Steeneveld W. M. Angevine E. Bazile A. Beljaars E. I. F. de Bruijn A. Cheng L. Conangla J. Cuxart M. Ek M. J. Falk F. Freedman H. Kitagawa V. E. Larson A. Lock J. Mailhot V. Masson S. Park J. Pleim S. S?derberg W. Weng M. Zampieri 《Boundary-Layer Meteorology》2011,140(2):177-206
We present the main results from the second model intercomparison within the GEWEX (Global Energy and Water cycle EXperiment) Atmospheric Boundary Layer Study (GABLS). The target is to examine the diurnal cycle over land in today??s numerical weather prediction and climate models for operational and research purposes. The set-up of the case is based on observations taken during the Cooperative Atmosphere-Surface Exchange Study-1999 (CASES-99), which was held in Kansas, USA in the early autumn with a strong diurnal cycle with no clouds present. The models are forced with a constant geostrophic wind, prescribed surface temperature and large-scale divergence. Results from 30 different model simulations and one large-eddy simulation (LES) are analyzed and compared with observations. Even though the surface temperature is prescribed, the models give variable near-surface air temperatures. This, in turn, gives rise to differences in low-level stability affecting the turbulence and the turbulent heat fluxes. The increase in modelled upward sensible heat flux during the morning transition is typically too weak and the growth of the convective boundary layer before noon is too slow. This is related to weak modelled near-surface winds during the morning hours. The agreement between the models, the LES and observations is the best during the late afternoon. From this intercomparison study, we find that modelling the diurnal cycle is still a big challenge. For the convective part of the diurnal cycle, some of the first-order schemes perform somewhat better while the turbulent kinetic energy (TKE) schemes tend to be slightly better during nighttime conditions. Finer vertical resolution tends to improve results to some extent, but is certainly not the solution to all the deficiencies identified. 相似文献