Evaluation of slope stability by finite element method using observed displacement of landslide   总被引：1，自引：0，他引：1  

Yasuo Ishii  Keiichi Ota  Senro Kuraoka  Ryosuke Tsunaki 《Landslides》2012,9(3):335-348

To monitor land deformation in detail, we ran a large-scale field test in which an artificial landslide was induced by the application of a load to a natural slope. The measured landslide displacement was reproduced numerically through the use of finite element model analysis with a two-dimensional elasto-viscoplastic model. The analysis suggested that the strength of the sliding surface decreased as the landslide mass moved. We propose a simple method for estimating safety factors. The method involves back-calculation of shear strength parameters through reproduction of observed landslide displacements and calculating the ratio of driving force to resisting force acting on the sliding surface as modeled by joint elements. This ratio, the “stability index”, shows the same trend as safety factors calculated by a two-dimensional limit equilibrium method and a shear strength reduction method that use back-calculated shear strength parameters estimated from the limit equilibrium state. The results indicate that the stability index may be applicable to the assessment of slope stability.  相似文献   

Spatial distribution of organic matter in the Bells CM2 chondrite using near‐field infrared microspectroscopy     

Yoko KEBUKAWA  Satoru NAKASHIMA  Michio ISHIKAWA  Kento AIZAWA  Tsutomu INOUE  Keiko NAKAMURA‐MESSENGER  Michael E. ZOLENSKY 《Meteoritics & planetary science》2010,45(3):394-405

Abstract– Distributions of organic functional groups as well as inorganic features were analyzed in the Bells (CM2) carbonaceous chondrite using near‐field infrared (NFIR) spectroscopy. NFIR spectroscopy has recently been developed to enable infrared spectral mapping beyond the optical diffraction limit of conventional Fourier transform infrared microspectroscopy. NFIR spectral mapping of the Bells 300 nm thick sections on Al plates for 7.5 × 7.5 μm² areas showed some C‐H‐rich areas which were considered to represent the organic‐rich areas. Heterogeneous distributions of organic matter as well as those of inorganic phases such as silicates (Si‐O) were observed with 1 μm spatial resolution. The NFIR mappings of aliphatic C‐H (2960 and 2930 cm^?1) and structural OH (3650 cm^?1) confirm that organic matter is associated with phyllosilicates as previously suggested. The NFIR mapping method can provide 1 μm spatial distribution of organic functional groups and their association with minerals. High local sensitivity of NFIR enables us to find organic‐rich areas and to characterize them by their aliphatic CH₂/CH₃ ratios. The aliphatic CH₂/CH₃ ratio of Bells is slightly higher than Murchison, similar to Orgueil, and lower than literature values of IDPs and cometary dust particles.  相似文献   

Effects of ocean particles on the upwelling radiance and polarized radiance in the atmosphere-ocean system     

Chong Shi  Pucai Wang  Teruyuki Nakajima  Yoshifumi Ota  Saichun Tan  Guangyu Shi 《大气科学进展》2015,32(9):1186-1196

Based on a vector radiative transfer model of the atmosphere-ocean system, the influence of oceanic components on radiation processes, including polarization effects, was investigated in the wavelength region ranging from 0.380 to 0.865 μm. The components considered were phytoplankton, inorganic suspended material (sediment), and colored, dissolved organic matter. Due to their important roles in oceanic radiation processes, the sensitivity of the bidirectional reflectance to the rough ocean surface, represented by the wind velocity 10 m above the ocean surface, and aerosol, were taken into account. The results demonstrated that both radiance and polarized radiance just below the ocean surface were sensitive to the change of the concentrations of the considered components, while the dependence of polarized radiance on the observation geometry was more sensitive than radiance. Significant differences in the specular plane existed between the impacts of the phytoplankton and sediment on the degree of polarization just above the ocean surface at 670 nm. At the top of the atmosphere (TOA), polarization was relatively insensitive to changing concentrations of ocean particles at longer wavelengths. Furthermore, the radiance at the TOA in the solar plane was more sensitive to the aerosol optical thickness than wind velocity. In contrast, wind velocity strongly influenced the radiance at the TOA in the sun glint region, while the polarization degree showed less dependence in that region. Finally, a nonlinear optimal inversion method was proposed to simultaneously retrieve the aerosol and wind velocity using radiance measurement.  相似文献   

Book review     

Ota Kulhanek 《Geophysical Journal International》1991,106(1):301-302

Book Reviewed in this Article:
Observatory seismology Ed. Litehiser, J. J., University of California Press, 1990, x + 379 pp, ISBN 0520 065824, US$ 48.  相似文献   

Degradation of common pharmaceuticals and personal care products in mixed solutions by advanced oxidation techniques   总被引：6，自引：6，他引：0  

R. R. Giri Ph.D.  H. Ozaki D.Eng.  S. Ota  R. Takanami M.Eng.  S. Taniguchi M.Eng. 《International Journal of Environmental Science and Technology》2010,7(2):251-260

Widespread detection of pharmaceutical compounds in water environment has been a serious concern recently, while conventional sewage treatments are ineffective for their elimination. But, advanced oxidation techniques are very promising to remove varieties of organic contaminants in water. This research aims to elucidate oxidation potentials of sixteen commonly used pharmaceutical compounds in mixed solutions by seven advanced oxidation techniques in laboratory batch experiments. The removal profiles exhibited four distinct patterns: a) easily degradable by all seven techniques, b) not easily degradable by all seven techniques, c) easily degradable by ozone-based techniques, but not by ultraviolet radiation-based techniques and d) easily degradable by ultraviolet radiation-based techniques, but not by ozone-based techniques. Ozone-based techniques rather than ultraviolet radiation-based techniques were very powerful for simultaneous removal of the compounds efficiently. Moreover, ozonation combined with ultraviolet radiation was the most appropriate technique for simultaneous removal of the tested compounds efficiently. Increased ozone dissolution and decomposition with ozone-based techniques did not always enhance the compounds’ removal. Physicochemical properties of the compounds and solution pH also presumably played an important role on the removal which merits further attention.  相似文献   

Evaluation of various satellite sensors for waterline extraction in a coral reef environment: Majuro Atoll, Marshall Islands   总被引：4，自引：0，他引：4  

Hiroya Yamano  Hiroto Shimazaki  Tsuneo Matsunaga  Albon Ishoda  Caleb McClennen  Hiromune Yokoki  Kazuhiko Fujita  Yoko Osawa  Hajime Kayanne 《Geomorphology》2006,82(3-4):398-411

The ability of five satellite sensor bands (IKONOS band 4, Terra ASTER bands 3 and 4, and Landsat ETM+ bands 4 and 5) was examined to extract the waterline at coral reef coasts (Majuro Atoll, Marshall Islands) using different wavelength regions (near infrared [NIR] and shortwave infrared [SWIR]) and different spatial resolutions (4, 15, and 30 m). After performing georeferencing and normalization of the images, density slicing was used to extract the waterline. Comparisons of extracted waterline positions with ground-level data for eight transects and global positioning system (GPS) tracks of the island shorelines showed that NIR bands were superior to SWIR bands because of the characteristics of the coral reef coasts, including a lack of foam and suspended sediments (which can affect the NIR wavelength region, if present) and the presence of remnant water on reef flats during low tide (which can affect the SWIR wavelength region). A linear relationship was found between the estimation errors of waterline positions and the spatial resolutions of the NIR sensors. Analysis on estimation errors and image costs showed that Terra ASTER band 3 was the most cost-effective sensor for extracting waterlines with reasonable accuracy. The results serve as general guidelines for using satellite-derived data to estimate intertidal topography and detect and monitor shorelines in coral reef environments.  相似文献   

Source parameters of selected earthquakes on the central and western margin of Afar     

Fekadu Kebede  Ota Kulh  nek 《Tectonophysics》1989,170(3-4):243-257

Spectral analysis of 196 short-period and long-period vertical- and horizontal-component seismograms from ten earthquakes on the central and western margin of Afar is performed to determine source parameters and discuss their tectonic implications. For the earthquakes in the regions under study, the stress drop varies from 2 to 31 bar while the seismic moment varies from 2 × 10²⁴ to 154 × 10²⁴ dyn cm. In general, low stress-drop values are obtained indicating the presence of softer material (especially for central Afar) at a shallower depth. It is observed that there is an increase in stress drop with the increase in moment-magnitude which in turn is obtained from the calculated average seismic moment. Energy estimates show that the mode of energy release is different in the two regions indicating that different tectonic processes are involved in the two regions. The slip rate obtained for the Serdo area is of the order of 1.6 cm/yr and is in close agreement with the spreading rate already obtained for central Afar. Spreading rates obtained earlier and that of the present study show a low spreading rate for Afar and neighbouring regions as compared to those of the other regions of the world.  相似文献   

Monitoring degradation of the 1995 Nojima earthquake fault scarps at Awaji Island, southwestern Japan     

Yoko Ota  Takashi Azuma  Mayumi Kobayashi 《Journal of Geodynamics》1997,24(1-4)

The Nojima fault on the northwestern coast of Awaji Island, south of Kobe, was reactivated during the January 17, 1995 Hyogoken-nanbu earthquake. This fault rupture was dominated by right-lateral offset (max. 1.7 m) along a high-angle reverse fault which has a maximum vertical displacement of 1.3 m on the southeastern side. We repeatedly measured seven profiles across the fault scarp in two areas (Hirabayashi to the northeast and Ogura to the southwest) for approximately 1 year following the earthquake. The original profile of the fault scarp was an overhanging scarp at Hirabayashi and Ogura, corresponding to the 70–80 ° dip of the fault plane. The fault scarp at Hirabayashi displaces Plio-Pleistocene siltstones of the Osaka Group and is overlain by a thin bed of unconsolidated gravel. The Ogura area is entirely underlain by the Osaka Group. Scarp degradation at Hirabayashi occurred by collapse of the gravel bed and proceeded more quickly than at Ogura, where fault scarp degradation proceeded mainly by exfoliation of the Osaka Group siltstones. The degradation occurred at a very fast rate until March at Hirabayashi, and until June or July at Ogura. Since then, the degradation has been very slow. Our data strongly indicate that the scarp profile was initially controlled mainly by the dip of the fault plane, and scarp degradation has been primarily controlled by lithological factors. The degradation of the Nojima earthquake fault scarp proceeded much more quickly than that of normal fault scarps in the western U.S.A., where many observations of the initial stages of scarp degradation have been carried out. The extremely rapid degradation of the Nojima fault scarp in weak late Neogene siltstones might, in combination with rapid cultural modification of the landscape, explain the paucity of geomorphic scarps along the numerous active faults in Japan. This observation may also have implications for tectonic geomorphology and paleoseismicity studies in other countries characterised by weak bedrock and moderate to high rainfall regimes.  相似文献   

Spatial and temporal variations of seismicity in the Horn of Africa from 1960 to 1993   总被引：2，自引：0，他引：2  

Atalay Ayele  Ota Kulhánek 《Geophysical Journal International》1997,130(3):805-810

Spatial and temporal variations of seismic energy release and b -value are investigated in the Horn of Africa. The results indicate that the area around the Afar Depression and southern Sudan is at a higher stress level than the southern Red Sea and Gulf of Aden. The distribution of earthquakes in the vicinity of Afar shows a systematic pattern and suggests the existence of two microplates (blocks) centred about the Danakil and Aisha horsts.  相似文献   

Seasonal variation of bromocarbons at Hateruma Island,Japan: implications for global sources     

Yoko Yokouchi  Takuya Saito  Jiye Zeng  Hitoshi Mukai  Stephen Montzka 《Journal of Atmospheric Chemistry》2017,74(2):171-185

High-frequency measurements of dibromomethane (CH₂Br₂) and bromoform (CHBr₃) at Hateruma Island, in the subtropical East China Sea, were performed using automated preconcentration gas chromatography/mass spectrometry. Their baseline concentrations, found in air masses from the Pacific Ocean, were 0.65 and 0.26 ppt, respectively, in summer and 1.08 and 0.87 ppt, respectively, in winter. Air masses transported from Southeast Asia were rich in bromocarbons, suggesting strong emissions in this area. The passage of cold fronts from the Asian continent was associated with sharp increases in observed concentrations of bromocarbons derived from coastal regions of the continent. Comparison of the relationships between [CH₂Br₂]/[CHBr₃] and [CHBr₃] in the Hateruma Island data with those in monthly mean data from 14 globally distributed U.S. National Oceanic and Atmospheric Administration ground stations suggested that these gases are produced primarily from a common process on a global scale.  相似文献