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1.
Characteristics and implication of clay minerals in the northern and southern parts of the Chelung-pu fault, Taiwan 总被引：1，自引：0，他引：1
In this study, we report the characteristics of clay minerals present in the Chelung-pu fault in Taiwan. In the 1999 Chi-Chi earthquake, different slip motions were recorded along the Chelung-pu fault in the northern and southern parts of the fault. The characteristics of clay minerals present in the fault zones can be attributed to the differences in motion. We analyzed the shallow drill core samples obtained from the northern and southern sites penetrating the fault. The clay minerals identified in most of the samples from both the sites are smectite, illite, and chlorite. There are illite–smectite mixed layers with a high illite content and no chlorite–smectite mixed layer. In some samples, no smectite is detected. We also examined the iron content and symmetry of iron and magnesium in the silicate and hydroxide layers in chlorite. At the northern site, the total iron content in chlorite of gouge is larger than that of the host rocks. On the other hand, at the southern site, the total iron content varies widely. It is hypothesized that the smectite consumption and differences in the characteristics of chlorite may be controlled by the differences in the lithology, fluid chemistry, fluid temperature, or fault activities (heating or breakage) between the northern and southern sites. 相似文献
2.
红外相机CASCAM光学设计 总被引：1，自引：1，他引：0
介绍紫金山天文台研制的光学-近红外相机CASCAM（Chinese Academy of Science，CAMera)的光学系统设计．CASCAM相机以红外列阵HAWAII-1和光学CCD为探测器，配备国家天文台兴隆观测站2．16米和1．26米望远镜进行0．4—2．5μm波长范围的成像和偏振成像观测．相机的光学系统由F／9→F／6缩焦系统和Offner反射成像系统构成．优化设计结果表明，光学设计方案已满足天文观测的要求．CASCAM相机在设计上实现了光学-近红外很宽波段的消色差变焦，并在楔形分柬片、常温滤光片轮和折射式焦面摆动技术等方面进行了新的尝试． 相似文献
3.
Jiro Koyama Chie Imakado Seiichi Uno Takako Kuroda Shouichi Hara Takahiro Majima Hideyuki Shirota Nathaniel C. Añasco 《Marine pollution bulletin》2014
To assess risks of chemically-dispersed oil to marine organisms, oil concentrations in the water were simulated using a hypothetical spill accident in Tokyo Bay. Simulated oil concentrations were then compared with the short-term no-observed effect concentration (NOEC), 0.01 mg/L, obtained through toxicity tests using marine diatoms, amphipod and fish. Area of oil concentrations higher than the NOEC were compared with respect to use and non-use of dispersant. Results of the simulation show relatively faster dispersion near the mouth of the bay compared to its inner sections which is basically related to its stronger water currents. Interestingly, in the inner bay, a large area of chemically-dispersed oil has concentrations higher than the NOEC. It seems emulsifying oil by dispersant increases oil concentrations, which could lead to higher toxicity to aquatic organisms. When stronger winds occur, however, the difference in toxic areas between use and non-use of dispersant is quite small. 相似文献
4.
Wook-Hyun Nahm Gyoo Ho Lee Dong-Yoon Yang Ju-Yong Kim Kenji Kashiwaya Masayoshi Yamamoto Aya Sakaguchi 《Journal of Paleolimnology》2010,43(3):489-498
This paper describes mean grain-size data from the 137Cs- and 210Pb-dated sediment core BS-3 (33-cm long) recovered from Jinheung Pond, located in the southwestern part of the Korean Peninsula.
Grain-size analysis of the Jinheung Pond sediments shows a clear signal for changes in annual precipitation over the past
60 years. Instrumental records of annual precipitation (AP) and the annual summation of the precipitation of >50 mm per day
(AP50), which reflects the energy available for sediment transport, correlate well with the mean grain-size distributions
measured in the core. The most plausible mechanism for this response in mean grain size is variations in the annual amount
and intensity of precipitation. Heavy precipitation enhances soil erosion over the catchment area and increases the transport
capacity of streams and rivers. Thus, coarser mean grain size should reflect higher precipitation, and smaller mean grain
size should reflect lower rainfall. In the data from core BS-3, however, grain-size peaks attributed to increased annual precipitation
are not prominent. This is because a dam prevents removal of fine particles from the pond via the outflow. Therefore, the
mean grain-size value represents somewhat larger sediments together with fine clays. The results of this study show that sediments
of dammed lakes and ponds are well suited for high-resolution environmental investigations, especially for records of changes
in precipitation over time. 相似文献
5.
Katsumi Hattori Peng Han Chie Yoshino Febty Febriani Hiroki Yamaguchi Chieh-Hung Chen 《Surveys in Geophysics》2013,34(3):293-316
In order to clarify the ultra low frequency (ULF) seismo-magnetic phenomena, a sensitive geomagnetic network has been installed in Kanto, Japan. In this study, we have analyzed geomagnetic data observed during the past decade in Izu and Boso Peninsulas. Energy of ULF geomagnetic signals at the frequency around 0.01 Hz has been investigated by wavelet transform analysis. To identify anomalous changes in ionospheric disturbances, the station Memabutsu has been chosen as a reference station. Case studies of magnitude 6 class earthquakes have demonstrated that there are unusual geomagnetic energy enhancements in the vertical component before the main shocks. Statistical studies by superposed epoch analysis have indicated that, before a sizeable earthquake, there are clearly higher probabilities of ULF anomalies than after the earthquake: statistical results of daily counts were found significant at about 3–4 weeks before, 1 week before, few days before, and 1 day after the event for Seikoshi station in Izu and around 2 weeks before, few days before, and 1 day after the event for Kiyosumi station in Boso, respectively. 相似文献
6.
Arito Sakaguchi 《Island Arc》1999,8(3):359-372
Abstract Thermal structural analysis and paleo-heat flow estimation provide clues to understanding the thermal evolution of the accretionary complex. The thermal structure and heat flow in the Jurassic Chichibu and Cretaceous to Tertiary Shimanto accretionary complex, Southwest Japan, have been investigated by vitrinite reflectance measurement and fluid inclusion analysis. As a result, the local and multistage metamorphisms were recognized as follows. First, the Tertiary complex around the Miocene Ashizuri granite underwent exposure to extra-high temperatures. Second, the Okitsu Melange underwent exposure to higher temperatures than the surrounding strata and was formed concurrently with the Kula-Pacific ridge subduction beneath the Japanese Islands in the Eocene. Finally, the thermal structure of most of the Cretaceous and southern Jurassic complexes is independent of the geologic structure, indicating that these areas suffered thermal overprint. Regional radiometric dating studies show that most of the Cretaceous Shimanto complex was heated in the Eocene; the thermal overprint might have occurred as a result of ridge subduction. The heat flow during peak heating was estimated to be 95–120 mW/m2 except for the Cretaceous Okitsu melange and the Cretaceous Nonokawa formation, north of the Okitsu Melange; a much higher value of heat flow of ~200 mW/m2 was estimated in the Okitsu Melange. An estimation of heat flow failed for the non-okawa formation because thermal equilibrium between the fluid and rocks has not yet been reached. It is probable that the southern strata underwent a higher heat flow. Such a trenchward increase in heat flow resembles the present situation of the Nankai Trough, although the heat flow in the Eocene was much higher. 相似文献
7.
K. Sakaguchi J. Tomono K. Okumura Y. Ogawa K. Matsuki 《Rock Mechanics and Rock Engineering》2008,41(2):325-341
Summary A tensile fracture of about 1 m in length was created by indenting wedges in a block of granite, and the heights of the two
fracture surfaces were measured using a large, non-contact surface profile measurement system with a laser profilometer to
determine the aperture distribution of the fracture. Based on the measured data, the frequency characteristics of the asperity
heights, the initial aperture (the aperture when the surfaces are in contact at a single point), and the size effect on the
statistical properties were analyzed. The results can be summarized as follows:
Authors’ address: Dr. Kiyotoshi Sakaguchi, Graduate School of Environmental Studies, Tohoku University, 6-6-20 Aramaki-Aza-Aoba,
Aoba-ku, Sendai 980-8579, Japan 相似文献
| 1. | The relation between the power spectral density of the fracture surface and the spatial frequency shows linearity on a log–log plot and thus the fracture surfaces can be assumed to be fractal object. On the other hand, the power spectral of the initial aperture becomes almost constant for wavelengths greater than about 100 mm. Thus, the matedness between the two surfaces of a fracture of 1 m monotonously increases with wavelength. |
| 2. | The standard deviation of the initial aperture increases with fracture size until the fracture size is about 200 mm, beyond which the standard deviation is almost independent of the fracture size. On the other hand, the mean initial aperture still increases when the fracture size exceeds 200 mm, since the initial aperture depends on the minimum value of the aperture, which decreases with the number of data points. |
8.
Shuro?YoshikawaEmail author Toshiya?Kanamatsu Kazuhisa?Goto Izumi?Sakamoto Masatoshi?Yagi Mikio?Fujimaki Riichirou?Imura Kenji?Nemoto Hide?Sakaguchi 《Geo-Marine Letters》2015,35(4):315-328
Ongoing geological research into processes operating on the nearshore continental shelf and beyond is vital to our understanding of modern tsunami-generated sediment transport and deposition. This paper investigates the southern part of Sendai Bay, Japan, by means of high-resolution seismic surveys, vibracoring, bathymetric data assimilation, and radioisotope analysis of a core. For the first time, it was possible to identify an erosional surface in the shallow subsurface, formed by both seafloor erosion and associated offshore-directed sediment transport caused by the 2011 Tohoku-oki tsunami. The area of erosion and deposition extends at least 1,100 m offshore from the shoreline down to water depths of 16.7 m. The tsunami-generated sedimentological signature reaches up to 1.2 m below the present seafloor, whereas bathymetric changes due to storm-related reworking over a period of 3 years following the tsunami event have been limited to the upper ~0.3 m, despite the fact that the study area is located on an open shelf facing the Pacific Ocean. Tsunami-generated erosion surfaces may thus be preserved for extended periods of time, and may even enter the rock record, because the depth of tsunami erosion can exceed the depth of storm erosion. This finding is also important for interpretation of modern submarine strata, since erosion surfaces in shallow (depths less than ~1 m) seismic records from open coast shelves have generally been interpreted as storm-generated surfaces or transgressive ravinement surfaces. 相似文献
9.
Aya Sakaguchi Masayoshi Yamamoto Keiichi Sasaki Kenji Kashiwaya 《Journal of Paleolimnology》2006,35(4):807-818
Distribution of uranium and thorium isotopes in a short sediment core obtained offshore of the Selenga Delta in Lake Baikal,
Siberia, was investigated to establish their sedimentary behaviors and to look for a linkage to paleoenvironmental changes.
The sediments were composed of dominantly fine detrital materials (70–85%) and a relatively high sedimentation rate (ca. 0.03 cm y−1). The depth profile of 238U content in bulk sediment samples showed a large variation of 70–123 Bq kg−1, while 232Th profile showed a relatively narrow range from 36 to 56 Bq kg−1. The observed 234U/238U activity ratios revealed a marked disequilibrium ranging from 1.53 to 1.84 with a mean value of 1.71 ± 0.07, demonstrating
the presence of 50–80% authigenic 238U in the bulk sediments. The distribution of this authigenic 238U did not display any clear correlation with variations in sediment composition (organic, carbonate, Bio-SiO2 and mineral contents) including grain size median. The profile of terrigenous 238U showed a relatively similar pattern to that of 232Th. Results of sequential leaching indicate that 238U in Fe–Mn oxyhydroxides fractions were responsible for the distribution of authigenic 238U rather than in Bio-SiO2 fraction. The distribution of authigenic 238U in the bottom sediments may be explained by the fluctuation of U adsorption capacity on particles including organic matter
and Fe–Mn oxyhydroxides before they entered the lake. This study highlights the potential use of authigenic and terrigenous
U (Th) signatures in sediments to trace the behavior of U (Th) and to reconstruct environmental (e.g., hydrological) changes
in the lake catchment area. 相似文献
10.
Assessment of nitrogen loading from the Kiso-Sansen Rivers into Ise Bay using stable isotopes 总被引：1，自引：0，他引：1
Ryo Sugimoto Akihide Kasai Kouichi Fujita Kenichi Sakaguchi Tomomi Mizuno 《Journal of Oceanography》2011,67(2):231-240
Concentrations of particulate organic nitrogen (PN), dissolved inorganic nitrogen (DIN), and their nitrogen isotope ratios
(δ
15N) in the Kiso-Sansen Rivers were determined from monthly observations over the course of a year to assess variations in the
form and sources of riverine nitrogen discharged into Ise Bay. The δ
15N values of NO3
− observed in the Kiso-Sansen Rivers showed a logarithmic decreasing trend from 8 to 0‰, which varied with the river discharge,
indicating mixing between point sources with high δ
15N and non-point sources with low δ
15N. The influence of isotope fractionation of in situ biogeochemical processes (mainly DIN assimilation by phytoplankton) on
δ
15N of NO3
− was negligible, because sufficient concentrations of NH4
+ for phytoplankton demand would inhibit the assimilation of NO3
−. A simple relationship between river discharge and δ
15N of NO3
− showed that the fraction of total NO3
− flux arising from point sources increased from 4.0–6.3% (1.1–1.8 tN day−1) during higher discharge (>600 m3 s−1) to 30.2–48.3% (2.6–4.1 tN day−1) during lower discharge (<300 m3 s−1). Riverine NO3
− discharge from the Kiso-Sansen Rivers can explain 75% of the variations in surface NO3
− at the head of Ise Bay over the year. 相似文献