Hydraulic and numerical study on the generation of a subaqueous landslide-induced tsunami along the coast   总被引：1，自引：0，他引：1  

Yoshinori Shigihara  Daichi Goto  Fumihiko Imamura  Yuichi Kitamura  Takayuki Matsubara  Kazuaki Takaoka  Kazuhiko Ban 《Natural Hazards》2006,39(2):159-177

By carrying out the hydraulic experiments in a one-dimensional open channel and two-dimensional basin, we clarified the process of how a landslide on a uniform slope causes the generation of a tsunami. The effect of the interactive force that occurs between the debris flow layer and the tsunami is significant in the generation of a tsunami. The continuous flow of the debris into the water makes the wave period of the tsunami short. The present experiments apply numerical simulation using the two-layer model with shear stress models on the bottom and interface, and the results are compared. The simulated debris flow shows good agreement with the measured results and ensures the rushing process into the water. We propose that the model use a Manning coefficient of 0.01 for the smooth slope and 0.015 for the rough slope, and a horizontal viscosity of 0.01 m²/s for the landslide; an interactive force of 0.2 for each layer is recommended. The dispersion effect should be included in the numerical model for the propagation from the shore.  相似文献   

Mechanism of the olivine–ringwoodite transformation in the presence of aqueous fluid     

Jun-ichi Ando  Naotaka Tomioka  Kazunari Matsubara  Toru Inoue  Tetsuo Irifune 《Physics and Chemistry of Minerals》2006,33(6):377-382

The mechanism of the high pressure transformation of olivine in the presence of aqueous fluid was investigated by high pressure experiments conducted nominally at the wadsleyite + ringwoodite stability field at 14.5 GPa and 700 and 800°C. The microstructures of recovered samples were observed using an analytical transmission electron microscope (ATEM) for which foils were prepared using a focused ion beam technique. Glass films approximately 1 μm in width always occupied the interface between olivine and hydrous ringwoodite. ATEM measurements showed that the chemical compositions of the glass films had approximately the same Mg/Fe ratio as that of olivine, but a higher Si content. Micro-structural and -chemical observations suggest that these glass films formed as quenched glass from the aqueous fluid dissolving olivine and that hydrous ringwoodite was crystallized from the fluid. This indicates that the transformation of olivine to hydrous ringwoodite was prompted by the dissolution–reprecipitation process. The dissolution–reprecipitation process is considered an important mineral replacement mechanism in the Earth’s crust by which one mineral is replaced by a more stable phase or phases. However, this process has not previously been reported for deep mantle conditions.  相似文献   

Curie temperature and lattice constant of oxidized titanomagnetite     

Tadashi Nishitani  Masaru Kono † 《Geophysical Journal International》1983,74(2):585-600

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Topography and landslides in weathered granitic rock areas—Hai Van landslide in central Vietnam     

Shinro Abe  Dinh Van Tien  Do Ngoc Ha  Takashi Hoshide  Tadashi Nishitani  Toyohiko Miyagi 《Landslides》2018,15(8):1675-1689

Many landslides occur every year during heavy rains at the Hai Van Pass and surrounding area in central Vietnam, where granitic rocks are distributed. As is common in granite areas, these landslides often occur as small-scale flow-type and slump-type landslides. However, several horseshoe-shaped loose slopes of widths and lengths of 500 to 800 m, which incorporate these landslides, are observed on slopes across the area. These topographies resemble those formed by past and present large-scale landslides. The presence of such a topography and the repeated occurrences of landslides within this topography are rare in granite areas, where shallow flow-type landslides are generally frequent. To understand the mechanism causing the landslides in the Hai Van region, and as a support for future risk assessment, the factors and processes leading to the formation of such a topography and their relationship with these landslides must be identified and assessed. This study investigated the history of past landslide movement in the Hai Van Pass and surrounding area through observations of drill cores and outcrops, and analysis of the direction of remanent magnetism in the granitic rocks. Mineral compositions, cracks, degrees of weathering, and topographic shapes of the granitic rocks and their relationship to the landslides occurring today were also investigated. The results of the study reveal no variation in the direction of remanent magnetism in the granitic rocks in the region that would indicate disturbance of the ground due to a past large-scale landslide. No evidence of such an event could also be found both in the drill cores and the rock outcrops. Further, results of the analysis of cracks and weathering pattern confirm that the topography of the region is affected by the weathering of the granitic rocks that progresses in concentric circles of various sizes. Thus, it can be concluded that these topographies were not formed by a singular large-scale landslide of the past, but rather by a composite of relatively shallow landslides occurring on the slope of dome structures unique to granite areas, which are formed by differential weathering and denudation regulated by cracks.  相似文献   

Simultaneous Observation of Solar Neutrons from the International Space Station and High Mountain Observatories in Association with a Flare on July 8, 2014     

Y. Muraki  D. Lopez  K. Koga  F. Kakimoto  T. Goka  L. X. González  S. Masuda  Y. Matsubara  H. Matsumoto  P. Miranda  O. Okudaira  T. Obara  J. Salinas  T. Sako  S. Shibata  R. Ticona  Y. Tsunesada  J. F. Valdés-Galicia  K. Watanabe  T. Yamamoto 《Solar physics》2016,291(4):1241-1265

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Direct correlation of radiolarian <Emphasis Type="Italic">Kilinora spiralis</Emphasis> Zone with the Late Jurassic ammonite faunal succession in the Kurisaka Formation,Kurosegawa Terrane,SW Japan     

Keisuke Ishida  Yasuyuki Tsujino  Takeshi Kozai  Tadashi Sato  Francis Hirsch 《中国科学D辑(英文版)》2009,52(12):1910-1923

The last appearance datum of the radiolarian Kilinora spiralis is recorded above the first appearance datum of the ammonite Ataxioceras (A.) kurisakense in the Todoro Section of the Kurisaka Formation, Southern Kurosegawa Terrane, Shikoku, SW Japan. The constraint by ammonite age prolongs the range of the Kilinora spiralis Zone, a remarkable Jurassic radiolarian zone in Japan-NW Pacific region, into the lower Kimmeridgian. The direct correlation of the Kilinora spiralis zone with the Late Jurassic ammonite faunal succession in the Kurisaka Formation will provide a clue to the still pending chronological difference between European and North American radiolarian zones.  相似文献   

Gradient field of undersea sound speed structure extracted from the GNSS-A oceanography     

Yokota  Yusuke  Ishikawa  Tadashi  Watanabe  Shun-ichi 《Marine Geophysical Researches》2019,40(4):493-504

Marine Geophysical Research - After the twenty-first century, the Global Navigation Satellite System-Acoustic ranging (GNSS-A) technique detected geodetic events such as co- and postseismic effects...  相似文献   

Interannual and Decadal Sea-Level Variations along the Japanese Coast   总被引：1，自引：0，他引：1  

Tomoharu Senjyu  Masaji Matsuyama  Naho Matsubara 《Journal of Oceanography》1999,55(5):619-633

Interannual (an annual to a decadal) and decadal sea-level variations along the Japanese coast have been investigated on the basis of monthly mean sea level during the period from 1951 to 1995. For the interannual variation, the Japanese coast is divided into six regions according to a regional similarity of sea level by using the cluster analysis, which is close to Tsumura's (1963) classification. The first mode of the Empirical Orthogonal Function (EOF) of the Interannual variation is the simultaneous rising and falling of the sea level along the Japanese coast. The first mode shows the largest variation in winter and has a negative correlation with the wintertime monsoon index; this suggests that the first mode is associated with a steric height change depending on the wintertime cooling intensity. The EOF second mode represents the Kuroshio large meander because strong negative eigenvectors are seen on the southeast coast of Japan and the time coefficient shows a high correlation with the Kushimoto-Uragami sea-level difference. For the decadal sea-level variation, the EOF first mode is a bi-decadal variation exhibiting simultaneous rising and falling of the sea level for the entire Japanese coast. The time coefficient of the first mode shows the first minimum in 1965, reaches a maximum in 1975, and decreases to the second minimum in 1984. The decrease from the mid-1970s and the increase from the mid-1980s to early 1990s correspond to the climatic regime shifts occurring in the same periods.  相似文献   

Encystment and excystment of <Emphasis Type="Italic">Gyrodinium instriatum</Emphasis> Freudenthal et Lee     

Tomoyuki Shikata  Sou Nagasoe  Tadashi Matsubara  Yasuhiro Yamasaki  Yohei Shimasaki  Yuji Oshima  Takuji Uchida  Ian R. Jenkinson  Tsuneo Honjo 《Journal of Oceanography》2008,64(3):355-365

In the present study, we have investigated the conditions influencing encystment and excystment in the dinoflagellate Gyrodinium instriatum under laboratory conditions. We incubated G. instriatum in modified whole SWM-3 culture medium and in versions of modified SWM-3 from which NO₃ ⁻, PO₄ ³⁻, NO₃ ⁻ + PO₄ ³⁻, or Si had been omitted and observed encystment. Percentage encystment was high in the media without N and without P, while the percentage encystment in the medium lacking both N and P was highest. Moreover, to investigate N or P concentration which induced the encystment, Gyrodinium instriatum was also incubated in media with different concentrations of inorganic N and P; the concentrations of NO₂ ⁻ + NO₃ ⁻ and PO₄ ³⁻ were measured over time. The precursors of cysts appeared within 2 or 3 days of a decrease in NO₂ ⁻ + NO₃ ⁻ or PO₄ ³⁻ concentration to values lower than 1 μM or 0.2 μM, respectively. When cysts produced in the laboratory were incubated, we observed excystment after 8–37 days, without a mandatory period of darkness or low temperature. We incubated cysts collected from nature at different temperatures or in the dark or light and observed excystments. Natural cysts excysted at temperatures from 10 to 30°C, in both light and dark, but excystment was delayed at low temperatures. These studies indicate that G. instriatum encysts in low N or P concentration and excysts over a wide temperature range, regardless of light conditions, after short dormancy periods.  相似文献   

Hydration-dehydration interactions between glycine and anhydrous salts: Implications for a chemical evolution of life     

Norio Kitadai  Tadashi Yokoyama 《Geochimica et cosmochimica acta》2011,75(21):6285-6299

Polymerizations of organic monomers including amino acids, nucleotides and monosaccharides are essential processes for chemical evolution of life. Since these reactions proceed with “dehydration” reactions, they are possibly promoted if combined with thermodynamically favorable “hydration” reactions of minerals and salts. To test the possibility, we conducted heating experiments of the simplest amino acid “glycine (Gly)” mixed with four simple anhydrous salts (MgSO₄, SrCl₂, BaCl₂ and Li₂SO₄) at 140 °C up to 20 days. Gly polymerization was strongly promoted by mixing with the salts in the order of MgSO₄ > SrCl₂ > BaCl₂ > Li₂SO₄. Up to 6-mer of Gly polymers were synthesized in the Gly-MgSO₄ mixture, and a total yield of Gly polymers attained about 7% of the initial amount of Gly by the 20 days heating. The total yield was about 200 times larger than that from the heating of Gly alone. XRD measurements of the Gly-MgSO₄ mixture revealed the generation of MgSO₄ monohydrate during Gly polymerization. These observations indicate that Gly polymerization was promoted by the salt hydrations through the hydration-dehydration interactions. Based on the observations, we tried to find a relationship between thermodynamic characteristics of the interactions and the promotion effects of each salt on Gly polymerization. It was found that the salts having lower hydration Δ_rG⁰ (easier to hydrate) promote Gly polymerization more strongly. The relationship was used to estimate promotion effects of simple oxide minerals on Gly polymerization. The estimations were consistent with previous observations about the effects of these minerals on Gly polymerization. The fact suggests that the hydration-dehydration interactions between amino acids and minerals are an important mechanism for amino acids’ polymerizations on minerals.  相似文献