Long-traveling landslides in deep snow conditions induced by the 2011 Nagano Prefecture earthquake,Japan     

Shintaro Yamasaki  Hidehisa Nagata  Takayuki Kawaguchi 《Landslides》2014,11(4):605-613

Earthquakes in mountainous areas may produce many landslides that involve abundant snow, but few observations have been made of these hazardous phenomena. The 12 March 2011 north Nagano Prefecture earthquake (M_JMA 6.7) occurred in a mountainous part of Japan that typically has an annual snow cover of more than 2 m, and it induced many snowy landslides. Some of these traveled relatively long distances. We examined the snowy Tatsunokuchi landslide to reconstruct the landsliding processes over deep snow. We infer that the Tatsunokuchi landslide occurred by collapse of a rock debris mass of 5?×?10⁴ m³ that plunged into the abundant snow, forming a mixture of snow and rock debris, which then traveled on top of the snow. Later, the displaced mass included a large amount of snow which was pushed forward at the front and to the sides. The velocity of the landslide was estimated to be approximately 14 m/s. It appears that the displaced mass, having only a small proportion of rock debris, had a low enough density to travel easily on top of the snow. Our observations suggest that there was much liquid water at the base of the displaced mass shortly after the event. Our results suggest that landslides may damage wider areas than expected if they travel over deep snow.  相似文献   

Abiki oscillations in Sakitsu Bay,west Kyushu,Japan     

Kenji Tanaka  Shinichiro Gohara  Takayuki Koga  Ryuta Yamaguchi  Fumihiko Yamada 《Natural Hazards》2014,74(1):233-250

Sakitsu and Yokaku bays in Amakusa in west Kyushu, Japan, experienced inundation damage in the February 2009 meteotsunami (Abiki) event. The oscillation characteristics of both bays are investigated by taking field measurements and conducting numerical experiments with regard to flood mitigation with the aim to reduce the flood impact during Abiki events. A continuous wavelet transform and bandpass filtering both of the pressure and water level indicated that a sequence of pressure disturbances, as small as 1.0 hPa, caused the large amplified oscillation within Sakitsu Bay. When a sequence of ocean long waves entered the bay, a surf beat evolved in the early stages. Subsequently, the sea level began to undergo large amplitude oscillations, and there was a secondary peak of oscillation with a period of around 24 min, as seen in both field measurements and numerical experiments. A surf beat with the period of 12 min formed in Yokaku Bay owing to the continuous incidence of ocean waves with period of 12 min, but its wave period was almost half of that of the natural period of the bay. This surf beat may have entered Sakitsu Bay with natural period of 11.8 min and caused large water-level fluctuations.  相似文献   

High precision oxygen three‐isotope analyses of anhydrous chondritic interplanetary dust particles     

Daisuke NAKASHIMA  Takayuki USHIKUBO  Michael E. ZOLENSKY  Noriko T. KITA 《Meteoritics & planetary science》2012,47(2):197-208

Abstract– Oxygen three‐isotope ratios of three anhydrous chondritic interplanetary dust particles (IDPs) were analyzed using an ion microprobe with a 2 μm small beam. The three anhydrous IDPs show Δ¹⁷O values ranging from ?5‰ to +1‰, which overlap with those of ferromagnesian silicate particles from comet Wild 2 and anhydrous porous IDPs. For the first time, internal oxygen isotope heterogeneity was resolved in two IDPs at the level of a few per mil in Δ¹⁷O values. Anhydrous IDPs are loose aggregates of fine‐grained silicates (≤3 μm in this study), with only a few coarse‐grained silicates (2–20 μm in this study). On the other hand, Wild 2 particles analyzed so far show relatively coarse‐grained (≥ few μm) igneous textures. If anhydrous IDPs represent fine‐grained particles from comets, the similar Δ¹⁷O values between anhydrous IDPs and Wild 2 particles may imply that oxygen isotope ratios in cometary crystalline silicates are similar, independent of crystal sizes and their textures. The range of Δ¹⁷O values of the three anhydrous IDPs overlaps also with that of chondrules in carbonaceous chondrites, suggesting a genetic link between cometary dust particles (Wild 2 particles and most anhydrous IDPs) and carbonaceous chondrite chondrules.  相似文献   

Influence of climate fluctuation on clay formation in the Baikal drainage basin     

Takayuki?SakaiEmail author  Koji?Minoura  Mitsuyuki?Soma  Yukinori?Tani  Atsushi?Tanaka  Fumiko?Nara  Nobuyasu?Itoh  Takayoshi?Kawai 《Journal of Paleolimnology》2005,33(1):105-121

Sedimentary cores BDP 96 and 98 and VER 96-2 St. 3 from Academician Ridge in Lake Baikal were investigated to investigate the effect of climatic fluctuations on rock weathering and clay formation in the Baikal drainage basin. Illite, smectite, vermiculite, and kaolinite were identified as the major clay minerals in the sediments by X-ray diffraction analysis. Biotite in gravels in alluvial soils of the Baikal drainage area weathers through illite to vermiculite, smectite, and finally to kaolinite. To investigate the relationship between weathering and climate, we measured the clay content and the concentration of biogenic silica in the sediments. High surface productivity (increased biogenic silica) and high chemical weathering (decreased clay content) occurred simultaneously, showing that crustal weathering and soil formation were enhanced under warm climatic conditions.Clay formation was enhanced in the watershed from the Late Miocene to the Middle Pliocene, and mechanical weathering of rocks increased during glacial intervals after the climate began to cool in Late Pliocene time. This change in the weathering mode in the watershed reduced the nutrient flux and aquatic productivity of Lake Baikal.  相似文献   

Extending Lagrangian perturbation theory to a fluid with velocity dispersion     

Masaaki Morita  Takayuki Tatekawa 《Monthly notices of the Royal Astronomical Society》2001,328(3):815-828

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The Ejection of Relativistic Bullets from Supernovae and the Generation of Gamma-Ray Bursts     

Umeda H 《The Astrophysical journal》2000,536(2):L89-L92

We present 1 μm Hubble Space Telescope/near-infrared camera and multiobject spectrometer resolved imaging polarimetry of the GG Tau circumbinary ring. We find that the ring displays east-west asymmetries in surface brightness as well as several pronounced irregularities but is smoother than suggested by ground-based adaptive optics observations. The data are consistent with a 37 degrees system inclination and a projected rotational axis at a position angle of 7 degrees east of north, determined from millimeter imaging. The ring is strongly polarized, up to approximately 50%, which is indicative of Rayleigh-like scattering from submicron dust grains. Although the polarization pattern is broadly centrosymmetric and clearly results from illumination of the ring by the central stars, departures from true centrosymmetry and the irregular flux suggest that binary illumination, scattering through unresolved circumstellar disks, and shading by these disks may all be factors influencing the observed morphology. We confirm a approximately 0&farcs;25 shift between the inner edges of the near-infrared and millimeter images and find that the global morphology of the ring and the polarimetry provide strong evidence for a geometrically thick ring. A simple Monte Carlo scattering simulation is presented that reproduces these features and supports the thick-ring hypothesis. We cannot confirm filamentary streaming from the binary to the ring, also observed in the ground-based images, although it is possible that there is material inside the dynamically cleared region that might contribute to filamentary deconvolution artifacts. Finally, we find a faint fifth point source in the GG Tau field that, if it is associated with the system, is almost certainly a brown dwarf.  相似文献   

Large-scale chaotically mixed sedimentary body within the Late Pliocene to Pleistocene Chikura Group, Central Japan     

Yuzuru  Yamamoto  Yujiro  Ogawa  Takayuki  Uchino  Satoru  Muraoka  Tae  Chiba 《Island Arc》2007,16(4):505-507

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Internal structure of the Nojima Fault zone from the Hirabayashi GSJ drill core   总被引：1，自引：0，他引：1  

Tomoyuki Ohtani  Hidemi Tanaka    Koichiro Fujimoto  Takayuki Higuchi  Naoto Tomida  Hisao Ito 《Island Arc》2001,10(3-4):392-400

Abstract The internal structures of the Nojima Fault, south-west Japan, are examined from mesoscopic observations of continuous core samples from the Hirabayashi Geological Survey of Japan (GSJ) drilling. The drilling penetrated the central part of the Nojima Fault, which ruptured during the 1995 Kobe earthquake (Hyogo-ken Nanbu earthquake) ( M 7.2). It intersected a 0.3 m-thick layer of fault gouge, which is presumed to constitute the fault core (defined as a narrow zone of extremely concentrated deformation) of the Nojima Fault Zone. The rocks obtained from the Hirabayashi GSJ drilling were divided into five types based on the intensities of deformation and alteration: host rock, weakly deformed and altered granodiorite, fault breccia, cataclasite, and fault gouge. Weakly deformed and altered granodiorite is distributed widely in the fault zone. Fault breccia appears mostly just above the fault core. Cataclasite is distributed mainly in a narrow (≈1 m wide) zone in between the fault core and a smaller gouge zone encountered lower down from the drilling. Fault gouge in the fault core is divided into three types based on their color and textures. From their cross-cutting relationships and vein development, the lowest fault gouge in the fault core is judged to be newer than the other two. The fault zone characterized by the deformation and alteration is assumed to be deeper than 426.2 m and its net thickness is > 46.5 m. The fault rocks in the hanging wall (above the fault core) are deformed and altered more intensely than those in the footwall (below the fault core). Furthermore, the intensities of deformation and alteration increase progressively towards the fault core in the hanging wall, but not in the footwall. The difference in the fault rock distribution between the hanging wall and the footwall might be related to the offset of the Nojima Fault and/or the asymmetrical ground motion during earthquakes.  相似文献   

Experiments on the Element Distribution between the Granodiorite JG-1a and 2M NaCl Hydrothermal Solution at Temperatures of 300 to 800°C and a Pressure of 1 kb     

Etsuo Uchida    Takuro Haitani    Takayuki Suetsugu    Takahiro Kashima  Ken Tsutsui 《Resource Geology》2003,53(2):155-161

Abstract. The distribution of Na, K, Ca, Mg, Mn and Fe between the granodiorite JG-la, one of the geochemical standard rocks, and 2M NaCl aqueous solution was experimentally determined at temperatures of 300 to 800C and a pressure of 1 kb using standard cold seal-type pressure vessels. The solid run products melted partially at 800C. Only K shows a significantly different behavior from the experiments using the basalt JB-la (Uchida and Tsutsui, 2000) due to the presence of ortho-clase in the JG-la. The transition elements tend to be preferably partitioned into the aqueous chloride solutions with increasing temperature. At 800C and 1 kb, the Fe concentration of the aqueous chloride solutions reached up to 5,000 ppm, and the Mn concentration up to 350 ppm. The distribution coefficient, K_{D, i} = C_{i, sol}/C_i, rock, is in the order of Na>K>Mn>Ca> Fe>Mg at 300C, but changed in the order of Mn>N>K>Fe>Ca>Mg at 800C. The distribution coefficients of the divalent cations for the JG-la are higher than those for the JB-1a. The distribution coefficient of the transition elements, Fe and Mn, increases significantly with increasing temperature. The thermodynamic analysis for aqueous speciation revealed that this is attributable to the formation of the tri-chloro complexes of the transition elements at higher temperatures.  相似文献   

Frequency-dependence of velocity and attenuation of elastic waves in granite under uniaxial compression     

Hitoshi Oda  Osamu Nishizawa  Kin'ichiro Kusunose  Takayuki Hirata 《Pure and Applied Geophysics》1990,133(1):73-85

Velocity as well as attenuation factorQ ^–1 ofP-wave in a dry granitic rock sample under uniaxial compressions were measured in the range of frequency between 100 kHz and 710 kHz by using the pulse transmission technique. Above the stress of 0.5 _f , where _f is the fracture stress, theP-wave velocity decreases with increasing axial stress, whereasQ ^–1 increases. Particularly, the change ofQ ^–1 is greater for high frequency than for low frequency. At a given stress level, the higher the frequency, the higher theP-wave velocity and the largerQ ^–1. This result means that the velocity decrease with increasing stress is smaller for higher frequency. Because of this frequency-dependence of velocity decrease, theP-wave in the rock under dilatant state shows dispersion. The body wave dispersion is more remarkable at higher stress, and is not found in a homogeneous material with no cracks. Thus the disperison is attributed to the generation of cracks. When the frequency-dependence ofQ ^–1 is approximated asf ⁿ in the present frequency range, the exponentn takes a value from 0.63 to 0.77.  相似文献