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21.
Yoshizawa Katsuaki 《Planetary and Space Science》1984,32(5):605-610
Relationships between the North-South asymmetry of the geomagnetic activity associated with the sector polarity of the interplanetary magnetic field (IMF) and various solar wind parameters are examined using the subauroral zone magnetic activity indices an and as. It is found that: (1) the effect of the sector polarity of IMF on the North-South asymmetry is due to the By-component of IMF, not to the Bx-component; (2) the asymmetry appears only when IMF is directed southward, being augmented by the increment of the magnitudes of the southward component and the solar wind velocity. 相似文献
22.
Auto-detection and integration of tectonically significant lineaments from SRTM DEM and remotely-sensed geophysical data 总被引：1，自引：0，他引：1
Alaa A. Masoud Katsuaki Koike 《ISPRS Journal of Photogrammetry and Remote Sensing》2011,66(6):818-832
A set of techniques was developed for automatically detecting tectonic lineaments from multi-source remotely-sensed data at various scales. The techniques include adaptive shading of grid data to enhance linear features, a segment-tracing algorithm to extract line segments from the shaded grid data, grouping of the segments by concatenating short segments, and connecting them by proximity and co-linearity criteria to form a lineament that represents significant tectonic structure. B-spline smoothing was adopted for lineament representation. Finally, a technique for assessing the orientations and styles of faulting (normal, reverse, and strike-slip types) was developed for use in characterizing the extrapolated fracture planes. The applicability of the developed techniques was examined using 30 arc-second topography/bathymetry grids, 1-min gravity anomaly grids, and 2-min total field magnetic intensity grids covering Egypt and its surroundings. Lineaments derived from data types so diverse in composition and from various depths corresponded well with the referenced tectonic features over much of the region. Prominent trends and faulting styles of lineaments provided important clues as to the timing of their development as well as strong support for a structural inheritance model. Results demonstrated the effectiveness of the developed techniques combined with integration of remotely-sensed data in detecting regional fracture systems accurately and in characterizing geodynamics over a long timeframe. 相似文献
23.
Incorporation of fracture directions into 3D geostatistical methods for a rock fracture system 总被引：2，自引：2，他引：0
Katsuaki?KoikeEmail author Chunxue?Liu Tomoji?Sanga 《Environmental Earth Sciences》2012,66(5):1403-1414
Simulating a rock fracture distribution is an important problem common to various fields in geosciences. This paper presents GEOFRAC, a geostatistical method to simulate a fracture distribution by incorporating the directions (strikes and dips) of the sampled fracture data into the simulation. Fracture locations are generated randomly following fracture densities assigned by a sequential Gaussian simulation. Fracture directions are transformed into an indicator set consisting of several binary (0 and 1) variables and the variables are compressed using the principal component analysis. Ordinary kriging is then employed to estimate the distributions of these principal values and the results are back-transformed into the coordinate system of the original indicator set. Fracture directions are generated randomly using their histograms within the defined directional interval. Finally, facets (fracture elements) are determined from the simulated locations and directions, and the fractures within the angle and distance tolerances are connected to form a fracture plane. From a case study of applying GEOFRAC to the fracture data in Kikuma granite, southwest Japan, GEOFRAC was shown to be able to depict a plausible fracture system because the simulated directions corresponded well to those measured. Furthermore, the simulated fracture system was available to estimate the hydraulic conductivity of the study site, which was roughly in agreement with the average of hydraulic test results. 相似文献
24.
Tectonic architecture through Landsat-7 ETM+/SRTM DEM-derived lineaments and relationship to the hydrogeologic setting in Siwa region, NW Egypt 总被引：2，自引：0，他引：2
Fracture zones on the Earth’s surface are important elements in the understanding of plate motion forces, the dynamics of the subsurface fluid flow, and earthquake distributions. However, good exposures of these features are always lacking in arid regions, characterized by flat topography and where sand dunes extensively cover the terrain. During field surveys these conditions, in many cases, hinder the proper characterization of such features. Therefore, an approach that identifies the regional fractures as lineaments on remotely-sensed images or shaded digital terrain models, with its large scale synoptic coverage, could be promising.In the present work, a segment tracing algorithm (STA), for lineament detection from Landsat-7 Enhanced Thematic Mapper Plus (ETM+) imagery, and the data from the Shuttle Radar Topographic Mission (SRTM) 30 m digital elevation model (DEM), has been applied in the Siwa region, located in the northwest of the Western Desert of Egypt. The objectives are to analyze the spatial variation in orientation of the detected linear features and its relation to the hydrogeologic setting in the area and the underlying geology, and to evaluate the performance of the algorithm applied to the ETM+ and the DEM data.Detailed structural analysis and better understanding of the tectonic evolution of the area could provide useful tools for hydrologists for reliable groundwater management and development planning. The results obtained have been evaluated by the structural analysis of the area and field observations. Four major vertical fracture zones were detected corresponding to two conjugate sets of strike-slip faults that governed the surface, and subsurface environments of the lakes in the region, and these correlate well with the regional tectonics. 相似文献
25.
The factors determining the suitability of limestone for industrial use and its commercial value are the amounts of calcium oxide (CaO) and impurities. From 244 sample points in 18 drillhole sites in a limestone mine, southwestern Japan, data on four impurity elements, SiO2, Fe2O3, MnO, and P2O5 were collected. It generally is difficult to estimate spatial distributions of these contents, because most of the limestone bodies in Japan are located in the accretionary complex lithologies of Paleozoic and Mesozoic age. Because the spatial correlations of content data are not clearly shown by variogram analysis, a feedforward neural network was applied to estimate the content distributions. The network structure consists of three layers: input, middle, and output. The input layer has 17 neurons and the output layer four. Three neurons in the input layer correspond with x, y, z coordinates of a sample point and the others are rock types such as crystalline and conglomeratic limestones, and fossil types related to the geologic age of the limestone. Four neurons in the output layer correspond to the amounts of SiO2, Fe2O3, MnO, and P2O5. Numbers of neurons in the middle layer and training data differ with each estimation point to avoid the overfitting of the network. We could detect several important characteristics of the three-dimensional content distributions through the network such as a continuity of low content zones of SiO2 along a Lower Permian fossil zone trending NE-SW, and low-quality zones located in depths shallower than 50 m. The capability of the neural network-based method compared with the geostatistical method is demonstrated from the viewpoints of estimation errors and spatial characteristics of multivariate data. To evaluate the uncertainty of estimates, a method that draws several outputs by changing coordinates slightly from the target point and inputting them to the same trained network is proposed. Uncertainty differs with impurity elements, and is not based on just the spatial arrangement of data points. 相似文献
26.
Magaia Luís André Koike Katsuaki Goto Tada-nori Masoud Alaa Ahmed 《Natural Resources Research》2019,28(3):1197-1215
Natural Resources Research - Unlike in coastal and sedimentary basins, regional-scale exploration of groundwater resources using only geophysical methods is costlier in consolidated rocks such as... 相似文献
27.
Distinguishing potential sources of arsenic released to groundwater around a fault zone containing a mine site 总被引：1，自引：1，他引：0
Arsenic (As) contamination in groundwater in mineralized areas typically results from the oxidation of As-rich sulfide minerals in aquifers, from hydrothermal alteration of geothermal systems, or as a result of anthropogenic influences such as mining activity. The primary goal of this study was to determine the spatial and temporal variance in As concentrations in shallow groundwater in a mineralized area and to identify the main As source controlling the concentration patterns. To this end, a combination of a geostatistical technique for space–time modeling of As concentrations and a numerical simulation, which models the transport of As in groundwater, is implemented. A study site in North Sulawesi, Sulawesi Island, Indonesia was selected as it was suitable for investigating the importance of fault lines and metal mining on As contamination. Initially, stable isotope analysis was used to ascertain the groundwater source and the mixing mechanism of the shallow and deep groundwater. Geostatistical modeling revealed consistent general patterns of As concentrations during the past 10 years, with high concentrations found along a NW–SE axis. By matching the geostatistical results with the distributions of As concentrations obtained through transport modeling, the deep-seated hydrothermal system along the fault zone was found to be the major As source. Wastewater from the mine was also observed to be a local As source. Another important influence on the As concentration pattern was a river, which acted as a boundary to separate the groundwater systems into two regions. 相似文献
28.
Yudi Adityawarman Arata Kaneko Koji Nakano Naokazu Taniguchi Katsuaki Komai Xinyu Guo Noriaki Gohda 《Journal of Oceanography》2011,67(2):173-182
A 30 km-range reciprocal sound transmission experiment was carried out on the line connecting Honshu and Shikoku (the first
and fourth biggest main Japanese islands, respectively) in the central part (Aki-nada) of the Seto Inland Sea, Japan, during
March–May 2010 to measure the mean current and temperature variations over the sea. The range-averaged current along the sound
transmission line was estimated to have a mean and standard deviation of (3.8–4.4) ± (1.7–1.8) cm/s after converting the travel
time difference data into currents, including a fortnightly tidal variation in the range of ±30 cm/s. The positive mean current
implies slow water movement from the west to east through Aki-nada. The range-averaged speed of sound was estimated by converting
from the mean travel time or one-way travel time into the speed of sound, and further converted into temperature for fixed
values of salinity and depth, according to the standard speed of sound formula. Besides the precise measurement (to an accuracy
of 0.01°C) of semidiurnal and diurnal tidal variations and seasonal warming, the temperature data showed periodic variations
with periods of 7.0 and 21.1 days that had never been observed in Aki-nada before. This study suggests that reciprocal sound
transmission is a powerful technique for the long-term accurate measurement of mean current and temperature variations in
coastal and inland seas. 相似文献
29.
Katsuaki Koike Toshiaki Minta Shinya Ishizaka Michito Ohmi 《Natural Resources Research》1996,5(1):23-32
An application of a geotechnical database system for primary evaluation of ground-water resources in a sedimentary basin is proposed. The database consists of 1200 borehole logs including geologic columns,in situ test results, ground-water level, water quality data, and resistivity logs. The Kumamoto plain, situated in southwest Japan, is chosen as a study area. The evaluation process consists of two steps: (1) modeling of shapes of water-bearing strata, and (2) modeling of distribution of physical quantity which has some relationship with the porosity of those strata. In step (1), the shapes of upper and/or lower surface of the pyroclastic flow deposits and the andesitic lava were determined, whereas the three-dimensional distribution model of resistivity was constructed from resistivity logging data obtained from 100 boreholes and using the proposed interpolation method in the step (2). An empirical equation between the porosity and the resistivity of the lava was also identified. The integration of two types of model and the empirical equation contributed to an estimate of the total volume of the ground-water under the study area. 相似文献
30.
Jean Aurelien Moukana Hisafumi Asaue Katsuaki Koike 《Environmental Earth Sciences》2013,70(4):1495-1506
This study aimed at clarifying the relationship between the dynamics of land use/land cover (LULC) changes and decline in the groundwater levels, and specifying an LULC category strongly affecting such decline in a Quaternary sedimentary basin. Groundwater level data recorded at 26 observation wells for a 14-year period in the Kumamoto Plain, central Kyushu, southwest Japan, were used for the analysis. The general trends of LULC were detected by a satellite image classification technique and surface spline method, which highlighted the decreases in groundwater-recharge materials. As the next step, those trends of groundwater levels that were closely correlated with rainfall were removed from the level data set, and the resultant residual component levels were applied to co-kriging analysis with LULC categories. Co-kriging provided a detailed map of groundwater level variability. Furthermore, we propose a method, prediction of residual of groundwater level (PWL), to infer future residual groundwater levels from the supposed LULC pattern by co-kriging-based modeling. PWL was demonstrated to be effective because it clearly represented the decrease and increase in negative residual level areas, depending on the extent of rice fields in the past and in predicted future distribution scenarios. 相似文献