The basement geology of Japan from A to Z     

Simon R. Wallis  Ken Yamaoka  Hiroshi Mori  Akira Ishiwatari  Kazuhiro Miyazaki  Hayato Ueda 《Island Arc》2020,29(1)

The Precambrian and lower Paleozoic units of the Japanese basement such as the Hida Oki and South Kitakami terranes have geological affinities with the eastern Asia continent and particularly strong correlation with units of the South China block. There are also indications from units such as the Hitachi metamorphics of the Abukuma terrane and blocks in the Maizuru terrane that some material may have been derived from the North China block. In addition to magmatism, the Japanese region has seen substantial growth due to tectonic accretion. The accreted units dominantly consist of mudstone and sandstone derived from the continental margin with lesser amounts of basaltic rocks associated with siliceous deep ocean sediments and local limestone. Two main phases of accretionary activity and related metamorphism are recorded in the Jurassic Mino–Tanba–Ashio, Chichibu, and North Kitakami terranes and in the Cretaceous to Neogene Shimanto and Sanbagawa terranes. Other accreted material includes ophiolitic sequences, e.g. the Yakuno ophiolite of the Maizuru terrane, the Oeyama ophiolite of the Sangun terrane, and the Hayachine–Miyamori ophiolite of the South Kitakami terrane, and limestone‐capped ocean plateaus such as the Akiyoshi terrane. The ophiolitic units are likely derived from arc and back‐arc basin settings. There has been no continental collision in Japan, meaning the oceanic subduction record is more complete than in convergent orogens seen in intracontinental settings making this a good place to study the geological record of accretion. Hokkaido lacks most of the Paleozoic history recognized in Honshu, Shikoku, Kyushu, and the Ryukyu Islands to the south and its geology reflects the Cenozoic development of two convergent domains with volcanic arcs, their approach, and eventual collision. The Hidaka terrane reveals a cross section through a volcanic arc and the main accretionary complex of the convergent system is represented by the Sorachi–Yezo terrane.  相似文献   

Improved numerical analysis for ultimate behavior of elastomeric seismic isolation bearings     

Ken Ishii  Masaru Kikuchi 《地震工程与结构动力学》2019,48(1):65-77

Elastomeric isolation bearings consist of multiple rubber layers with their top and bottom surfaces bonded to steel plates to restrict compressive deformation. Deformation constraints result in a variation of elastic modulus over the cross section of the rubber layers. In this paper, we describe a normalized compression modulus distribution on a circular rubber pad. The compressive and bending moduli of the rubber pad can be reproduced by applying the distribution to a series of axial springs. We also present a mechanical model for predicting the behavior of elastomeric seismic isolation bearings subject to large shear deformation and high compressive load. The mechanical model consists of a series of multiple shear springs at midheight and a series of axial springs at the top and bottom interfaces of the bearing. Simulation analyses of bearing tests were conducted to validate the proposed model. The analyses demonstrated that a model for circular lead-rubber bearings can successfully capture the influence of the axial load magnitude on the bearing shear behavior. The new model can simulate much more realistic behavior than prior models based on a uniform modulus assumption.  相似文献   

Wave plus current over a ripple-covered bed     

Jrgen Fredse  Ken H. Andersen  B. Mutlu Sumer 《Coastal Engineering》1999,38(4):594

  相似文献   

Correlation between Expansion Rate of the Coronal Magnetic Field and Solar Wind Speed in a Solar Activity Cycle     

Kazuyuki?HakamadaEmail author  Masayoshi?Kojima  Tomoaki?Ohmi  Munetoshi?Tokumaru  Ken’ichi?Fujiki 《Solar physics》2005,227(2):387-399

Thirteen synoptic maps of expansion rate of the coronal magnetic field (CMF; RBR) calculated by the so-called ‘potential model’ are constructed for 13 Carrington rotations from the maximum phase of solar activity cycle 22 through the maximum phase of cycle 23. Similar 13 synoptic maps of solar wind speed (SWS) estimated by interplanetary scintillation observations are constructed for the same 13 Carrington rotations as the ones for the RBR. The correlation diagrams between the RBR and the SWS are plotted with the data of these 13 synoptic maps. It is found that the correlation is negative and high in this time period. It is further found that the linear correlation is improved if the data are classified into two groups by the magnitude of radial component of photospheric magnetic field, |B^pho_r|; group 1, 0.0 G ≦ |B_r^pho| < 17.8 G and group 2, 17.8 G ≦ |B_r^pho|. There exists a strong negative correlation between the RBR and the SWS for the group 1 in contrast with a weak negative correlation for the group 2. Group 1 has a double peak in the density distribution of data points in the correlation diagram; a sharp peak for high-speed solar wind and a low peak for low-speed solar wind. These two peaks are located just on the axis of maximum variance of data points in the correlation diagram. This result suggests that the solar wind consists of two major components and both the high-speed and the low-speed winds emanating from weak photospheric magnetic regions are accelerated by the same mechanism in the course of solar activity cycle. It is also pointed out that the SWS can be estimated by the RBR of group 1 with an empirical formula obtained in this paper during the entire solar activity cycle.  相似文献   

Primary production and community respiration in a warm streamer associated with Kuroshio warm core ring in spring     

Mitsuyasu Waku  Ken Furuya 《Journal of Oceanography》1998,54(5):565-572

Daily rates of gross primary production, net community production and community respiration were determined in spring of 1997 at two stations in a warm streamer off Sanriku, Japan fromin vitro changes in dissolved oxygen. The phytoplankton community was composed of chlorophytes, cryptophytes and prymnesiophytes as determined by biomarker pigment analysis. Gross production, integrated from the surface to its 1% light level was 52.5 and 80.4 mmol O₂ m⁻²d⁻¹. The difference in gross production is ascribed to variations in photosynthetic activity of the population. Community respiration was 17.4 and 49.5 mmol O₂ m⁻²d⁻¹, and positive net community production was found within the euphotic zone. The contribution of autotrophic and heterotrophic respiration to community respiration was estimated on the basis of the observed respiration and the phytoplankton composition. Heterotrophic respiration was calculated to be highly variable and the observed difference in community respiration was due to heterotrophic respiration. Heterotrophic respiration was considered to play an important role in the rapid mineralization of organic materials.  相似文献   

Tropospheric delay correction with dense GPS network in L1-SAIF augmentation   总被引：2，自引：0，他引：2  

Noboru Takeichi  Takeyasu Sakai  Sounosuke Fukushima  Ken Ito 《GPS Solutions》2010,14(2):185-192

The L1-SAIF (L1 Submeter-class Augmentation with Integrity Function) signal is one of the Quasi-Zenith Satellite System (QZSS) navigation signals, which provides an augmentation function for mobile users in Japan. The tropospheric delay correction in the L1-SAIF augmentation is discussed in detail. Because the topographical features in Japan are complicated, the correction information is generated from GPS observation data collected at 200 GPS stations which are densely distributed over Japan. A total of 210 Tropospheric Grid Points (TGPs) are arranged to fully cover Japan. The TGPs that provide the correction information are selected adaptively to achieve the expected correction accuracy. This selection of TGPs is provided by the TGP mask message. Mobile users acquire the zenith tropospheric delay (ZTD) value at neighboring TGPs from the correction messages, and can estimate the local ZTD value accurately by using a suitable ZTD model. Only up to seven L1-SAIF messages are sufficient to provide the full correction information. Accuracy evaluations have proven that it is possible to achieve a correction accuracy of 13.4 mm RMS. The strategy presented here has been implemented into the augmentation system using the L1-SAIF signal, and its application guidance is presented in the QZSS interface specification.  相似文献   

Significance of stemflow in groundwater recharge. 1: Evaluation of the stemflow contribution to recharge using a mass balance approach     

Makoto Taniguchi  Maki Tsujimura  Tadashi Tanaka 《水文研究》1996,10(1):71-80

Stemflow was evaluated in a water balance and its contribution to groundwater recharge determined. Gross precipitation, throughfall and stemflow were measured for one year in a pine forest (Tsukuba, Japan) to determine each component of the water balance in the forest. Groundwater recharge rates by stemflow and throughfall were calculated from a mass balance method using chloride in subsurface waters. The stemflow in the water balance was relatively small when estimated as a value per canopy projected area of the tree in the forest. However, the results for the mass balance of chloride in subsurface waters indicated that it was impossible to disregard the stemflow in determining groundwater recharge. Although the ratio of stemflow to the net precipitation was small in the water balance, the effect of stemflow on groundwater recharge was relatively large.  相似文献   

Determination of the freshwater origin of Coastal Oyashio Water using humic-like fluorescence in dissolved organic matter     

Yu Mizuno  Jun Nishioka  Takahiro Tanaka  Yuya Tada  Koji Suzuki  Yuta Tsuzuki  Atsuko Sugimoto  Youhei Yamashita 《Journal of Oceanography》2018,74(5):509-521

Coastal Oyashio Water (COW), defined as a water mass with a temperature lower than 2 °C and a salinity lower than 33.0, is distributed in the North Pacific Ocean off southeastern Hokkaido, Japan, from winter to spring. COW is rich in macronutrients and dissolved iron and is thus considered to affect the spring phytoplankton blooms in the Oyashio region. Although river water and sea-ice melt water have been considered freshwater end-members of COW, the contributions of these freshwater sources to COW have not been well described. In this study, the humic-like components in dissolved organic matter were first applied as a parameter to evaluate the freshwater end-members of COW in March 2015. Linear regressions with negative slopes were determined between the humic-like components and the salinity of COW. The intercepts of the regressions against the humic-like components were within the ranges of those observed for the local rivers of Hokkaido but were very different from those of sea ice. These findings suggest that river water contributed to the COW observed here as a freshwater end-member, although the contribution of sea-ice melt water to COW could not be evaluated. This novel approach also highlighted two different less-saline water masses in COW. The first was characterized by a lower temperature and relatively high levels of humic-like components, while the second was higher in temperature and had higher levels of humic-like components. It is suggested that these different characteristics are due to the contributions of water from different rivers and/or different effects of sea-ice melt water.  相似文献   

Deep sea circulation of particulate organic carbon in the Japan Sea     

Shigeyoshi Otosaka  Takayuki Tanaka  Orihiko Togawa  Hikaru Amano  Eugeny V. Karasev  Masayuki Minakawa  Shinichiro Noriki 《Journal of Oceanography》2008,64(6):911-923

Seasonal and spatial variations of particulate organic carbon (POC) flux were observed with sediment traps at three sites in the Japan Sea (western and eastern Japan Basin and Yamato Basin). In order to investigate the transport processes of POC, radiocarbon (¹⁴C) measurements were also carried out. Annual mean POC flux at 1 km depth was 30.7 mg m⁻²day⁻¹ in the western Japan Basin, 12.0 mg m⁻²day⁻¹ in the eastern Japan Basin and 23.8 mg m⁻²day⁻¹ in the Yamato Basin. At all stations, notably higher POC flux was observed in spring (March–May), indicating biological production and rapid sinking of POC in this season. Sinking POC in the high flux season showed modern Δ¹⁴C values (>0‰) and aged POC (Δ¹⁴C < −40‰) was observed in winter (December–January). The Δ¹⁴C values in sinking POC were negatively correlated with aluminum concentration, indicating that Δ¹⁴C is strongly related to the lateral supply of lithogenic materials. The Δ¹⁴C values also showed correlations with excess manganese (Mn_xs) concentrations in sinking particles. The Δ¹⁴C-Mn_xs relationship suggested that (1) the majority of the aged POC was advected by bottom currents and incorporated into sinking particles, and (2) some of the aged POC might be supplied from the sea surface at the trap site as part of terrestrial POC. From the difference in the Δ¹⁴C-Mn_xs relationships between the Japan Basin and the Yamato Basin, we consider that basin-scale transport processes of POC occur in the Japan Sea.  相似文献   

Lagrangian observation of phytoplankton dynamics at an artificially enriched subsurface water in Sagami Bay,Japan     

Takako Masuda  Ken Furuya  Naoko Kohashi  Mitsuhide Sato  Shigenobu Takeda  Makoto Uchiyama  Naho Horimoto  Takashi Ishimaru 《Journal of Oceanography》2010,66(6):801-813

Phytoplankton dynamics in the lower euphotic zone were observed by tracking a subsurface water released at 20-m depth from Takumi, an artificial upwelling device. Takumi continually discharged seawater pumped up from a depth of 205 m: this water was mixed with 5-m depth water to adjust the density to that of 20-m depth water of Sagami Bay, Japan. The discharged water was pulse-labeled at Takumi with uranine and tracked for 63.9 h with a drifting buoy equipped with a drogue at 20-m depth. We present a simple model to estimate in situ phytoplankton net growth rates from temporal changes in phytoplankton abundance in the discharged water with correction for the influence of water exchange between the discharged water and neighboring layers. Lagrangian observation showed active growth of pico- and nanophytoplankton, especially cryptophytes and Synechococcus (Cyanobacteria), in the subsurface layer. In contrast, diatoms grew little in spite of micromolar concentrations of nutrients. The active growth of pico- and nanophytoplankton was in good agreement with shipboard serial dilution culture experiments. The low growth activity of diatoms was suggested to be related to low light availability in the subsurface layer.  相似文献