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111.
About 2000 active faults are known to exist within the land area of Japan. Most of these active faults have deformed the topographic surfaces which were formed in the late Quaternary, including fluvial terraces; and the formative ages of these terraces are estimated mainly by tephrochronology. Fluvial terraces in the eastern Hokuriku region, comprising the Toyama, Tonami, and Kanazawa Plains, northern central Japan, are widely distributed and have been deformed by reverse active faults. The formative age of terraces in this area has not been reported, as volcanic ash deposits are rarely visible within terrace deposits and the overlying loamy soil, and outcrops of fluvial terraces are quite scarce in this area. In the present study, we carried out a drilling survey on these terraces to obtain samples of the overlying loamy soil and upper part of terrace deposits. From these samples, we extracted some well-known widespread volcanic ash, from which we were able to estimate the approximate age of the terraces and the vertical slip rate of the active faults. Late Quaternary fluvial terraces in eastern Hokuriku are divided into 12 levels: Terraces 1 to 12 in descending order. Widespread tephras such as the Kikai-Tozurahara Tephra (K-Tz: 95 ka) are contained in the lowest part of the loamy soil in Terrace 4 and the Daisen-Kurayoshi Pumice (DKP: 55 ka) is present in the lowest part of the loamy soil in Terrace 6. From the ages and the vertical displacements of the fluvial terraces, the late Quaternary average vertical slip rates of active faults in eastern Hokuriku are estimated to be 0.2–0.9 mm/year (Uozu fault), 0.1–0.4 mm/year (Kurehayama fault), 0.1–0.3 mm/year (Takashozu fault), 0.1–0.4 mm/year (Hohrinji fault), and 0.5–0.8 mm/year (Morimoto-Togashi fault). We also estimated the recurrence interval of earthquakes related to active faults from displacement per event and ages of terraces and no significant difference in vertical displacement per single earthquake for different active faults, and recurrence intervals tend to be inversely proportional to vertical displacement rates. This study demonstrates that a combination of drilling of loamy soil and precise cryptotephra analysis of fluvial terraces can be used to estimate the formative age of the terraces and the average slip rate of active faults in areas where volcanic ash deposits are rare. 相似文献
112.
Katayama Y Oura T Iizuka M Orita I Cho KJ Chung IY Okada M 《Marine pollution bulletin》2003,47(1-6):85-90
Effects of spilled oil on microbial communities in tidal flats were examined by use of a simulator for a tidal flat ecosystem. The simulator is composed of a wave generator, a tide control device, and a tidal flat. Sediment for the tidal flat was obtained at a natural tidal flat in Hiroshima Bay, Japan. After stabilizing the benthic organisms, fuel oil C was added to the surface of the flat at 1 lm(-2). Although the total number of micro-organisms remained at 1.5-3.5 x 10(9) cells g(-1) dry sediment irrespective of the addition of oil, bacterial communities which were analyzed based on the 16S rDNA showed clear changes after the addition of fuel oil C and after a subsequent recovery period. Bacterial colonies were randomly isolated from the oil-supplemented sediment during the experiments, and the isolates were examined for susceptibility to hydrocarbons in order to screen the oil-susceptible bacteria. The proportion of oil-susceptible bacteria in the isolates decreased with the addition of the oil. Oil-susceptible bacteria showed an inability to assimilate petroleum compounds as well as an inhibition of growth. The possibility of using oil-susceptible bacteria as an indicator of bioremediation in tidal flats was discussed. 相似文献
113.
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115.
Daisuke Nishio-Hamane Asa Shimizu Ritsuko Nakahira Ken Niwa Asami Sano-Furukawa Taku Okada Takehiko Yagi Takumi Kikegawa 《Physics and Chemistry of Minerals》2010,37(3):129-136
The stability and equation of state for the cotunnite phase in TiO2 were investigated up to a pressure of about 70 GPa by high-pressure in situ X-ray diffraction measurements using a laser-heated
diamond anvil cell. The transition sequence under high pressure was rutile → α-PbO2 phase → baddeleyite phase → OI phase → cotunnite phase with increasing pressure. The cotunnite phase was the most stable
phase at pressures from 40 GPa to at least 70 GPa. The equation of state parameters for the cotunnite phase were established
on the platinum scale using the volume data at pressures of 37–68 GPa after laser annealing, in which the St value, an indicator of the magnitude of the uniaxial stress component in the samples, indicates that these measurements were
performed under quasi-hydrostatic conditions. The third-order Birch-Murnaghan equation of state at K
0′ = 4.25 yields V
0 = 15.14(5) cm3/mol and K
0 = 294(9), and the second-order Birch-Murnaghan equation of state yields V
0 = 15.11(5) cm3/mol and K
0 = 306(9). Therefore, we conclude that the bulk modulus for the cotunnite phase is not comparable to that of diamond. 相似文献
116.
基于格网数据的洪水灾害风险评估方法——以日本新川洪灾为例 总被引:13,自引:1,他引:12
本文对日本格网统计数据的历史、体系以及结构进行了介绍 ,并应用地理信息技术给出了各级格网的自动生成方法。同时以 2 0 0 0年日本新川洪水灾害为案例 ,建立了二维洪水演进水动力学模型 ,并采用地理信息系统与水动力学模型结合的方法对新川破堤洪水泛滥进行了模拟 ,同时对洪泛区灾害损失进行了评估 ,得到的结果为进一步评估洪水灾害风险以及确定合理的洪灾保险费率奠定了基础 ,对于格网统计数据在城市规划以及城市减灾等领域的应用也有一定的借鉴意义。 相似文献
117.
Usu volcano (Hokkaido, Japan) is a dacitic volcano, known for its high production rate of lava domes and crypto-domes. It is thus a good target to study processes of volcanic dome evolution (upheaval and/or relaxation). We carried out repeated GPS and microgravity surveys on the three most recent domes of Mt. Usu (1910: Meiji Shinzan; 1943–1945: Showa-Shinzan and 1977–1982: Usu-Shinzan). The repeat period was 1 to 2 months and extended from October 1996 to June 1997. We also compare new data with results from former studies. More than 20 years after the start of Usu-Shinzan dome growth, there is still subsidence at a maximum rate of about 7 to 8 cm/year. The reasons for this subsidence are discussed. Repeated gravity surveys revealed an increase of gravity on the domes (about 60±10 microgal/year for Usu-Shinzan, about 15 microgal at Showa-Shinzan and 10 to 20 microgal for Meiji-shinzan); this gravity increase exceeds that expected due to subsidence. We discuss and interpret the excess gravity change in terms of a density increase in the edifice, caused by a combination of processes (contraction of the edifice, water level change, devesiculisation, cooling and magma intrusion). Quantification of these processes at Usu volcano may help to understand the processes of evolution at domes on other volcanoes such as Merapi (Indonesia), Unzen (Japan) or Montserrat (West Indies). 相似文献
118.
An intensification of auroral luminosity referred to as an auroral break-up often accompanies the onset of geomagnetic pulsation (Pi 2) at the dip-equator. One such auroral break-up occurred at 2239 UT on 16 June, 1986, being accompanied by weak substorm activity (AE≈50 nT) which was recorded in all-sky image of Syowa Station, Antarctica (66.2°S, 71.8°E in geomagnetic coordinates). The associated Pi 2 magnetic pulsation was detected by a fluxgate magnetometer in the afternoon sector at the dip-equator (Huancayo, Peru; 1.44°N, 355.9° in geomagnetic coordinates; 12.1°S, 75.2°W in geographic coordinates; L = 1.00). In spite of the large separation of the two stations in longitude and latitude, the auroral break-up and subsequent luminosity modulation were seen to be correlated with the wave form of the ground Pi 2 pulsation. This occurred in such a way that the luminosity maximum was seen to occur at the phase of maximum amplitudes of Pi 2 wave form. We argue that the observed correlation could be interpreted as indicating a Pi 2-modulation of a field-aligned acceleration of the low energy electrons that may occur near the equator of the midnight magnetosphere. 相似文献