Discovery of Jurassic ammonoids from the Shyok suture zone to the northeast of Chang La Pass, Ladakh, northwest India and its tectonic significance   总被引：1，自引：0，他引：1  

Masayuki  Ehiro  Satoru  Kojima  Tadashi  Sato  Talat  Ahmad  Tomoyuki  Ohtani 《Island Arc》2007,16(1):124-132

Abstract   Callovian (late Middle Jurassic) ammonoids Macrocephalites and Jeanneticeras were recovered from the Shyok suture zone, northeast of Chang La Pass, Ladakh, northwest India. They are the first reliable Jurassic fossils and the oldest chronologic data from the Shyok suture zone. The ammonoid-bearing Jurassic strata, newly defined as the Tsoltak Formation, consist largely of terrigenous mudstone with thin sandstone beds and were probably a part of the continental basement to the Cretaceous Ladakh Arc.  相似文献   

Tsunami Assessment for Risk Management at Nuclear Power Facilities in Japan     

Ken Yanagisawa  Fumihiko Imamura  Tsutomu Sakakiyama  Tadashi Annaka  Tomoyoshi Takeda  Nobuo Shuto 《Pure and Applied Geophysics》2007,164(2-3):565-576

The present study focuses on evaluation of the maximum and minimum water levels caused by tsunamis as risk factors for operation and management at nuclear power facilities along the coastal area of Japan. Tsunamis generated by submarine earthquakes are examined, basing literature reviews and databases of information on historical tsunami events and run-up heights. For simulation of water level along the coast, a numerical calculation system should be designed with computational regions covering a particular site. Also the calculation system should be verified by comparison of historical and calculated tsunami heights. At the beginning of the tsunami assessment, the standard faults, their locations, mechanisms and maximum magnitudes should be carefully estimated by considering historical earthquake-induced tsunamis and seismo-tectonics at each area. Secondly, the range of errors in the model parameters should be considered since earthquakes and tsunamis are natural phenomena that involve natural variability as well as errors in estimating parameters. For these reasons, uncertainty-induced errors should be taken into account in the process of tsunami assessment with parametric study of the tsunami source model. The element tsunamis calculated by the standard fault models with the errors would be given for the design. Then, the design tsunami can be selected among the element tsunamis with the most significant impact, maximum and minimum water levels, on the site, bearing in mind the possible errors in the numerical calculation system. Finally, the design tsunami is verified by comparison with the run-up heights of historical tsunamis, ensuring that the design tsunami is selected as the highest of all historical and possible future tsunamis at the site.  相似文献   

The abundance of helium in prominences and in the chromosphere     

Tadashi Hirayama 《Solar physics》1971,19(2):384-400

The abundance of helium relative to hydrogen is spectroscopically determined in prominences and in the chromosphere by using 1952, 1958, 1962 and 1966 eclipse data. Care is taken in the intensity calibration of emission lines, the self-absorption, and the departure from local thermodynamic equilibrium. We find from the line profiles and intensities of prominences and the chromosphere that the neutral helium lines are emitted in the metal-hydrogen emitting region where the kinetic temperature is low enough, 6000 8000 K, so that only the ionization due to UV radiation from the corona can explain the intensity of neutral helium emission. Also we find that the intensity ratio of Hei 3888.65 to H₈ 3889.05 increases towards the upper boundaries of prominences and of the chromosphere and that it approaches to a universal limiting value, both in various prominences or in the chromosphere, where it is considered that the ionization of neutral helium and hydrogen is nearly complete. From these facts the helium to hydrogen number ratio is found to be 6.5 ± 1.5%.A new schematic model of the chromosphere is presented where spicules have no hot region of emitting neutral helium lines. Here it is suggested that the kinetic temperature of spicules, 6000 8000 K, would be primarily determined by the radiation temperature of the corona and the transition region beyond the Lyman continuum of hydrogen which happens to be around those temperatures.  相似文献   

The influence of the brightness of the asteroidal dust bands on the gegenschein     

Tadashi Mukai  Masanori Fujino  Ryosuke Nakamura  Fumihiko Usui 《Icarus》2003,162(2):337-343

The position and shape of the Gegenschein’s maximum brightness provide information on the structure of the interplanetary dust cloud. We show that the asteroidal dust bands, extended near the anti-solar point, play an important role in determining both the position of the maximum brightness and the shape of the Gegenschein. After removing the asteroidal dust bands from an observation of the Gegenschein on November 2, 1997, it was found that the maximum brightness point shifted −0.4° in ecliptic latitude, i.e., to the south of the ecliptic plane, at an ecliptic longitude of 180°, in contrast to a latitude value of +0.1° when the dust bands were included. Furthermore, the part of the Gegenschein to the south of the ecliptic plane was brighter than the northern part at the time of observation. Referring to the cloud model of T. Kelsall et al. (1998, Astrophy. J. 508, 44-73), it can be estimated that the ascending node of the symmetry plane of the dust cloud is 57°^−3°_+7° when its inclination is 2.03° ? 0.50°.  相似文献   

Some instabilities in the 3/1 and 2/1 resonances     

Tadashi Yokoyama  Massae Sato  Masayoshi Tsuchida 《Celestial Mechanics and Dynamical Astronomy》1987,41(1-4):99-105

In a very simple way, it is possible to show the existence of small regions of instability, inside the observed 3/1 and 2/1 Kirkwood Gap, by using the classical Laplace-Lagrange secular theory.  相似文献   

Japanese Astrometry Satellite Mission for Infrared Exploration     

Naoteru Gouda  Takuji Tsujimoto  Yukiyasu Kobayashi  Tadashi Nakajima  Naoki Yasuda  Hideo Matsuhara 《Astrophysics and Space Science》2002,280(1-2):89-94

JASMINE is the name of a Japanese infrared (K-band) scanning astrometric satellite. JASMINE (I and/or II-project) is planned to be launched between 2013 and 2017 and will measure parallaxes and proper motions with the precision of 10μas at K≃ 12 - 15 mag. JASMINE will observe a few hundred million stars belonging to the disk and the bulge components of our Galaxy, which are hidden by the interstellar dust extinction in optical bands. Furthermore, JASMINE will also obtain photometry of stars in K, J and H-bands. The main objective of JASMINE is to study the most fundamental structure and evolution of the disk and the bulge components of the Milky Way Galaxy. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Recovery of entire shocked samples in a range of pressure from ~100 GPa to Hugoniot elastic limit          下载免费PDF全文

Keita Nagaki  Toshihiko Kadono  Tatsuhiro Sakaiya  Tadashi Kondo  Kosuke Kurosawa  Yoichiro Hironaka  Keisuke Shigemori  Masahiko Arakawa 《Meteoritics & planetary science》2016,51(6):1153-1162

We carried out laser shock experiments and wholly recovered shocked olivine and quartz samples. We investigated the petrographic features based on optical micrographs of sliced samples and found that each recovered sample comprises three regions, I (optically dark), II (opaque), and III (transparent). Scanning electron microscopy combined with electron backscattered diffraction shows that there are no crystal features in the region I; the materials in the region I have once melted. Moreover, numerical calculations performed with the iSALE shock physics code suggest that the boundary between regions II and III corresponds to Hugoniot elastic limit (HEL). Thus, we succeeded in the recovery of the entire shocked samples experienced over a wide range of pressures from HEL (~10 GPa) to melting pressure (~100 GPa) in a hierarchical order.  相似文献   

Accretionary Orogens of the Japanese Islands and Their Comparison with the Central Asian Orogenic Belt: Sr-Nd-Hf Isotopic Evidence     

JAHN Bor-ming  USUKI Masako  ISHIHARA Shunso  OKAMOTO Kazuaki  USUKI Tadashi 《《地质学报》英文版》2013,87(Z1):302-304

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Numerical modelling study on the flexural uplift of the Transantarctic Mountains     

Tadashi Yamasaki  Hideki Miura  Yoshifumi Nogi 《Geophysical Journal International》2008,174(1):377-390

In this study, based on a 2-D thermomechanical finite element model, the uplift of the Transantarctic Mountains (TAM) is discussed in relation to the flexural uplift of a rheologically layered lithosphere, which is described by Vening-Meinesz's cantilever kinematics. The general model behaviour shows that the thickness of the crust and the geothermal gradient in the lithosphere are the principal factors in controlling the effective elastic thickness ( T _e). Although T _e is also significantly dependent on the magnitude of the uplift and the wet or dry rheological condition of rocks, these two factors do not have a dominant influence on the half-wavelength of the TAM. The model with a plausible crustal structure beneath Antarctica shows that the thermal structure beneath East Antarctica is the critical factor, controlling the half-wavelength of the TAM. If there is a significant radiogenic heat source in the Antarctic lithosphere, T _e beneath East Antarctica is estimated to be 50 km, at most, and the lithosphere has no potential to explain an exceptionally large-scale half-wavelength of the TAM. Even for the model without a heat source, if East Antarctica is significantly thermally influenced by West Antarctica, T _e is estimated to be about 60 km, and it is difficult to reproduce the half-wavelength of the TAM. Contrarily, when a radiogenic heat source is absent and the thermal structure beneath East Antarctica is not significantly affected by that beneath West Antarctica, the rheological structure beneath East Antarctica has the potential to reproduce the half-wavelength of the TAM ( T _e∼ 100 km). Thus, the presence of a radiogenic heat source in the crust and mantle and the thermal influence of West Antarctica on East Antarctica are crucial factors in the reproduction of the half-wavelength found in the TAM.  相似文献   

Field experiments on remediation of coastal sediments using granulated coal ash     

Kyunghoi Kim  Tadashi Hibino  Tamiji Yamamoto  Shinjiro Hayakawa  Yugo Mito  Kenji Nakamoto  In-Cheol Lee 《Marine pollution bulletin》2014

Field experiments were carried out to evaluate the effect of Granulated Coal Ash (GCA) on remediation of coastal sediments in terms of removing phosphates and hydrogen sulfide. Phosphate concentrations in the sediment were kept below 0.2 mg/l after the application of GCA, whereas those in the control sites increased up to 1.0 mg/l. The concentration of hydrogen sulfide in the sediment was maintained at almost zero in the experimental sites (GCA application sites) for over one year, whereas it ranged 0.1–2.4 mg S L⁻¹ in control sites. Meanwhile, individual number of benthos increased in the experimental sites by several orders of magnitude compared to the control sites. The major process involved in hydrogen sulfide removal by GCA was thought to be the increase in pH, which suppresses hydrogen sulfide formation. From our findings, we concluded that GCA is an effective material for remediating organically enriched coastal sediment.  相似文献