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   

Toxicity of 17alpha-ethynylestradiol and norethindrone,constituents of an oral contraceptive pill to the swimming and reproduction of cladoceran Daphnia magna,with special reference to their synergetic effect     

Goto T  Hiromi J 《Marine pollution bulletin》2003,47(1-6):139-142

Toxicity of 17alpha-ethynylestradiol (EE2) and norethindrone (NOR), constituents of low dosage oral contraceptives, was assessed for the freshwater cladoceran Daphnia magna. Acute toxicity tests showed that 5 ppm of EE2, the highest concentration in this study, never inhibited swimming, whereas NOR inhibited swimming at >3 ppm: 48 h EC(50) for NOR was 6.41 ppm. Chronic toxicity tests were carried out for 25 days by measuring the number of offspring, moltings and sex ratios of neonates at 20, 100 and 500 ppb. EE2>100 ppb significantly decreased the number of offspring to 75% of the control; however, no effect was observed in molting and sex ratios at <500 ppb. NOR did not affect reproduction and sex ratios at <500 ppb. Mixture of EE2 (5.88 ppb) and NOR (94.12 ppb) also significantly decreased the number of offspring to 57% of the control. This result indicates the importance of examining synergetic effects of chemicals in the context of natural environments which face exposure to myriad chemicals.  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   

The 1992 Cairo earthquake: A case study of a small destructive event     

Attia El-Sayed  Ronald Arvidsson  Ota Kulhánek 《Journal of Seismology》1998,2(4):293-302

On 12 October 1992, an earthquake, magnitude mb = 5.9 and M s = 5.2, hit the City of Cairo, Egypt. It was this century's largest earthquake in northern Egypt with related destruction in the City of Cairo, the Nile Valley and the Nile Delta areas. Our source parameter determinations show that the 1992 earthquake had a normal faulting mechanism, seismic moment M o = 5.2 × 1017 Nm, centroid depth of 23 km and a source time function duration of 3 seconds. The mechanism is compared with those corresponding to two other events that occurred in the northern Red Sea. The similarity between the mechanisms as well as the spatial distribution of the geological faults around Cairo suggest seismic activity along the extension of the stress field of the Red Sea rift system to the area around the City of Cairo. This situation affects the level of seismic hazard in the Cairo area. The 1992 earthquake belongs to an unusual class of relatively small, M w > 6.0, yet destructive earthquakes. The damage caused by these events is usually attributed to their shallow focal depth, 5 km, and to amplification of seismic waves in the local soil beneath the damaged structures. However, the Cairo earthquake deviates from other events of this class since the focal depth was determined to be 23 km. We calculated synthetic accelerograms for the 1992 earthquake with the loose sediments observed in the Nile Valley, and show that this enhanced the amplitude of the acceleration by a factor of two. However, the determined accelerations, about 0.5 m s-2, cannot alone explain the relatively large amount of damaged structures. Hence, a major cause to the destruction is likely the poor state of construction of the Cairo buildings.  相似文献   

Has the 1998 regime shift also occurred in the oceanographic conditions and lower trophic ecosystem of the Oyashio region?     

Hiromi Kasai  Tsuneo Ono 《Journal of Oceanography》2007,63(4):661-669

To examine whether the regime shift in 1998 that has been variously reported to have occurred in the oceanographic conditions of the central and eastern North Pacific also occurred in the Oyashio region, western North Pacific, we compared data over the period 1990–2003. Oceanographic conditions were compared before 1997 with those after 1998, using the A-line dataset (1990–2003) obtained by the oceanographic surveys of the Hokkaido National Fisheries Research Institute, Fisheries Research Agency (HNFRI/FRA). Seasonal changes of the monthly-mean SST (as temperature in the surface layer) show a significant increase in spring after 1998. After 1998, the mean concentration of chlorophyll a at the surface was higher in spring than that before 1997. This was more remarkable in the main current of the Oyashio. These changes suggest that the spring phytoplankton bloom in the Oyashio region after 1998 was larger in magnitude and initiated earlier. Consumption of nutrients during the spring bloom and standing stock of netplankton also shows a distinct difference between the time period before 1997 and after 1998. These results support the occurrence of the regime shift around 1998 in the Oyashio region. The changes of hydrographical conditions accompanying with the 1998 regime shift are discussed. The hydrographic mechanism of enhancement of primary productivity during the spring phytoplankton bloom was not fully clarified, though. Results in this study may support the usefulness of the A-line dataset for analysis of long-term variability in the western subarctic Pacific.  相似文献   

Depolymerized pyribole structures derived from talc by heating     

Hiromi Konishi  Junji Akai 《Physics and Chemistry of Minerals》1991,17(7):569-582

Talc specimens heated to 700–1450° C were examined with an analytical high-resolution transmission electron microscope. Neither the amphibole-like structure nor the MPP structure (M = mica, P = pyroxene-layer), proposed by Avgustinik and Vigdergauz (1948) and Sueno et al. (1980), was found. On the contrary, a disordered pyribole structure was observed. This pyribole showed a structure disordered in terms of chain widths, with single and double chains predominant. A local MPP structure with 4–6 repeated units of (21) sequence was generally observed in a disordered region. The electron diffraction data were consistent with maximum symmetry A2/m for the proto-MPP structure. A HRTEM study of the fine structures associated with the depolymerization of talc was the basis of a structural model proposed for the depolymerization of biopyriboles. In this model, a pair of (010) faults with a displacement of 1/2 (a+c) took an important role. The acceptor and donor regions model was also discussed.  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   

Positional isomer composition of monounsaturated fatty acids from a lacustrine sediment     

Hiromi Matsuda  Tadashiro Koyama 《Geochimica et cosmochimica acta》1977,41(2):341-345

From the surface sediment of a eutrophic lake (Japan), the double bond position in the monounsaturated fatty acids (C₁₅-C₂₆) has been determined by combined gas chromatography-mass spectrometry of the methoxylated derivatives. The relative abundance of 11-octadecenoic acid, suggested to be of bacterial origin, is higher in the chloroform-methanol extract than the extract by saponification.  相似文献   

The spectrum of short-period seismic noise     

Ota Kulhánek 《Studia Geophysica et Geodaetica》1966,10(4):472-475

Резюме Приводятся спектры короткопериодических помех в диапазоне частот 1–3 гц. Регистрация помех была проведена электромалнитным вертикальным сейсмографом на станции Кашперске Горы. В исследованном частотном диапазоне выл установлен один максимум при частотеf≐ гц. Положение этого максимума в зависимости от времени в течение одного года (1962) изменяется незначительно (табл. 1, фиг. 2a). Амплитуды максимумов изменяются в щироком диапазоне 34–50 ϱ∂. Целью анализа было получить информации о спектральных сбойствах короткопериодических помех с точки зрения проекта подходяшей системы для их фильтрации.

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