Survey of dioxins in Tokyo Bay bottom sediment     

Hosomi M  Matsuo T  Dobashi S  Katou S  Abe H 《Marine pollution bulletin》2003,47(1-6):68-73

This paper examines dioxin profiles in bottom sediments from Tokyo Bay, Japan using sedimentation dating based on 210Pb measurements and dioxin measurements based on particle size distributions. Dioxin concentrations in surface sediment ranged from 3.2 to 52 pg-TEQ g(-1), with the concentrations in the bay back and central region being higher than those at the front of the bay. The vertical dioxin concentration in sediment core samples showed peak levels from years 1962 to 1980, with the maximum being 110 pg-TEQ g(-1). Principal component analysis indicates that the main source of dioxins in bottom sediment from the back of bay are herbicides such as CNP, while in the front of bay atmospheric deposition due to incineration activities are responsible. Dioxins in bottom sediment were mainly found in the particles <75 microm in size.  相似文献   

Dynamic Rupture in a 3-D Particle-based Simulation of a Rough Planar Fault     

Steefen Abe  Shane Latham  Peter Mora 《Pure and Applied Geophysics》2006,163(9):1881-1892

An appreciation of the physical mechanisms which cause observed seismicity complexity is fundamental to the understanding of the temporal behaviour of faults and single slip events. Numerical simulation of fault slip can provide insights into fault processes by allowing exploration of parameter spaces which influence microscopic and macroscopic physics of processes which may lead towards an answer to those questions. Particle-based models such as the Lattice Solid Model have been used previously for the simulation of stick-slip dynamics of faults, although mainly in two dimensions. Recent increases in the power of computers and the ability to use the power of parallel computer systems have made it possible to extend particle-based fault simulations to three dimensions. In this paper a particle-based numerical model of a rough planar fault embedded between two elastic blocks in three dimensions is presented. A very simple friction law without any rate dependency and no spatial heterogeneity in the intrinsic coefficient of friction is used in the model. To simulate earthquake dynamics the model is sheared in a direction parallel to the fault plane with a constant velocity at the driving edges. Spontaneous slip occurs on the fault when the shear stress is large enough to overcome the frictional forces on the fault. Slip events with a wide range of event sizes are observed. Investigation of the temporal evolution and spatial distribution of slip during each event shows a high degree of variability between the events. In some of the larger events highly complex slip patterns are observed.  相似文献   

Evaluation of tsunami impacts on shallow marine sediments: An example from the tsunami caused by the 2003 Tokachi-oki earthquake, northern Japan     

Atsushi Noda  Hajime Katayama  Tsumoru Sagayama  Kazuya Suga  Yasuhito Uchida  Kenji Satake  Kohei Abe  Yukinobu Okamura 《Sedimentary Geology》2007,200(3-4):314-327

A combined approach of field geology and numerical simulation was conducted for evaluating the tsunami impacts on the shelf sediments. The 2003 Tokachi-oki earthquake, M 8.0, that occurred on 25 September 2003 off southeastern Hokkaido, northern Japan, generated a locally destructive tsunami. Maximum run-up height of the tsunami waves reached 4 m above sea level. In order to estimate the tsunami impacts on shallow marine sediments, we compared pre- and post-tsunami marine sediments in water depths of 38–112 m in terms of grain size, sedimentary structure, and microfossil content. Decreases of fine fractions, especially finer than very fine sand, which led to coarsen the mean grain size, were detected in the inner shelf of the northern part of the study area. Foraminiferal assemblages also changed in the coarsened sediments. On the other hand, the other shelf sediments largely unchanged or slightly fined. We also simulated the tsunami wave velocity and direction, and grain size entrained by the modeled tsunami. The numerical simulation resulted in that the 2003 tsunami could transport very fine sand in water depths shallower than 45–95 m at the northern part of the study area. This is comparable with the actual grain-size changes after the tsunami had passed. However, some storms and tidal currents might also be possible to stir the surface sediments after the pre-tsunami survey, so we could not conclude that the grain-size changes had been caused only by the tsunami. Nevertheless, a combined approach of sampling and modeling was powerful for estimating the tsunami impacts under the sea.  相似文献   

Physical size of tsunamigenic earthquakes of the northwestern Pacific     

Katsuyuki Abe 《Physics of the Earth and Planetary Interiors》1981,27(3):194-205

The new scale M_t of tsunami magnitude is a reliable measure of the seismic moment of a tsunamigenic earthquake as well as the overall strength of a tsunami source. This M_t scale was originally defined by Abe (1979) in terms of maximum tsunami amplitudes at large distances from the source. A method is developed whereby it is possible to determine M_t at small distances on the basis of the regional tsunami data obtained at 30 tide stations in Japan. The relation between log H, maximum amplitude (m) and log Δ, a distance of not less than 100 km away from the source (km) is found to be linear, with a slope close to 1.0. Using three tsunamigenic earthquakes with known moment magnitudes M_w, for calibration, the relation, M_t = log H + log Δ + D, is obtained, where D is 5.80 for single-amplitude (crest or trough) data and 5.55 for double-amplitude (crest-to-trough) data. Using a number of tsunami amplitude data, M_t is assigned to 80 tsunamigenic earthquakes that occurred in the northwestern Pacific, mostly in Japan, during the period from 1894 to 1981. The M_t values are found to be essentially equivalent to M_w for 25 events with known M_w. The 1952 Kamchatka earthquake has the largest M_t, 9.0. Of all the 80 events listed, at least seven unusual earthquakes which generated disproportionately-large tsunamis for their surface-wave magnitude M_s are identified from the relation. From the viewpoint of tsunami hazard reduction, the present results provide a quantitative basis for predicting maximum tsunami amplitudes at a particular site.  相似文献   

Tsunami propagation in rivers of the Japanese Islands     

Kuniaki Abe 《Continental Shelf Research》1986,5(6)

On 26 May 1983 the rivers of the Japanese Islands were invaded by a tsunami from the Sea of Japan. Water levels in five large rivers were measured and were highest midway towards the uppermost point of inundation. The level at the uppermost point was approximately the same as that at the river mouths. As a result of resonance, a standing wave develops in the rivers. The period of the invading tsunami was found to be 80 min. This continental shelf oscillation resulted in a long-wave propagation of the tsunami.The water levels showed another peak in the neighbourhood of estuarine inflows. The period of this wave was estimated to be 20 min; its formation was attributed to generation near the tsunami source.The cross-section and longitudinal profiles of the rivers, together with water flow, complicated the observed water level profiles.  相似文献   

Textural analysis and flow mechanism of the Donzurubo subaqueous pyroclastic flow deposits     

T. Yamazaki  I. Kato  I. Muroi  M. Abe 《Bulletin of Volcanology》1973,37(2):231-244

The Donzurubo subaqueous pyroclastic flow deposits deposited in subaqueous environments maintaining high temperatures (about 500°C). Each flow unit of these pyroclastic flow deposits shows some characteristic size distributions in its stratigraphic column. The concentration of pumice at the top clearly defines the top facies of a flow unit. Median diameter (Md Ø) and the averages of the largest ten essential dense debris increase gradually starting from both the top and the bottom of the flow unit. The maximum points of Md Ø and the averages of the largest ten essential dense debris are usually found in the middle zone of each flow unit, but the Md Ø maximum points are generally in a lower position than the averages. Mechanical analyses show that the deposits consist of polymodal populations. They show, on the whole, an asymmetrical distribution, which is mainly due to the absence of the coarser fractions of the main population. The size distribution characteristics and the C-M pattern of the deposits suggest that these subaqueous pyroclastic flow deposits were not originated by homogeneously suspended turbulent flows but by incandescent turbulent flows with layered suspension.  相似文献   

Synthesis of analcime from volcanic sediments in sodium silicate solution     

Hiroshi Abe  Morihiro Aoki  Hiroshi Konno 《Contributions to Mineralogy and Petrology》1973,42(2):81-92

Analcime has been synthesized from natural rhyolitic tuff and green tuff (Miocene age) at 200° C and 20 kg/cm² with solution of Na₂SiO₃ (12%) in 50- to 260-hr runs. From the diffraction intensities, it was found that the alteration products of green tuff contained more analcime than those of rhyolitic tuff. It has been concluded that the lithological character of starting materials and the chemical behavior of reaction products are important controlling factors in analcimization.  相似文献   

Effects of light intensity on the production of VSLs from the marine diatom Ditylum brightwellii     

Abe  Minami  Okuda  Yuki  Hashimoto  Shinya 《Journal of Atmospheric Chemistry》2022,79(1):1-16

Journal of Atmospheric Chemistry - Very short-lived substances (VSLs) are known to play an important role in ozone depletion in the troposphere and stratosphere. Environmental factors that...  相似文献   

Insight into nitrous oxide production processes in the western North Pacific based on a marine ecosystem isotopomer model   总被引：2，自引：0，他引：2  

Chisato Yoshikawa  Hitomi Abe  Maki N. Aita  Florian Breider  Keichi Kuzunuki  Sakae Toyoda  Nanako O. Ogawa  Hisami Suga  Naohiko Ohkouchi  Sebastian O. Danielache  Masahide Wakita  Makio C. Honda  Naohiro Yoshida 《Journal of Oceanography》2016,72(3):491-508

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Factors influencing maintenance and decline of a diatom bloom in the Yatsushiro Sea,Japan     

Goh Onitsuka  Tomoyuki Shikata  Saho Kitatsuji  Kazuo Abe  Takeshi Yamamoto  Hiroki Ochiai  Hitoshi Matsuo 《Journal of Oceanography》2016,72(4):617-627

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