Activity of IGCP-368 During 1999     

Masaru Yoshida  M. Santosh  Chandra B. Dissanayake 《Gondwana Research》2000,3(2):261

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Neoproterozoic Deformation at a Boundary Zone Between the Nellore-Khammam Schist Belt and Pakhal Basin, SE India: Strain Analysis of Deformed Pebbles     

Rajneesh Kumar  Takamoto Okudaira  Masaru Yoshida 《Gondwana Research》2000,3(3)

In the Kinnerasani area in southeastern India, the terrain boundary between the Archean Nellore-Khammam Schist Belt and the Proterozoic Pakhal Supergroup overlying the Dharwar-Bastar cratons can be observed. We analyzed the mesoscopic and microscopic structural features of the highly deformed pebbles in the basal conglomerate bed of the Pakhal Supergroup that occurs at the terrain boundary. The results of the analysis of the pebbles suggest that: 1) deformation of pebbles resulted from ductile deformation during peak metamorphism 2) the mode of strain is plane strain to constrictive and maximum elongation located to be vertical and 3) the apparent stretch of the pebbles is up to 300%.In the Nellore-Khammam Schist Belt, quartz grains constituting the quartz layer of the feldspathized gneiss folded by the last-phase deformation also show vertical maximum stretching in constrictive strain. This observation suggests that the deformational features, at least the mode of strain, during the last-phase deformation is comparable to the deformation forming elongated pebbles of the Pakhal conglomerate. The last-phase deformation structures of the Nellore-Khammam Schist Belt are well observed near the terrain boundary. This indicates that the Pakhal deformation overprinted the rocks of the Nellore-Khammam Schist Belt near the boundary, and that their tectonic juxtaposition occurred during or before this deformation period. Because the Pakhal deformation took place during or soon after the peak metamorphism of the Pakhal Supergroup, which is known to be 1000 Ma, and the last metamorphism of the Nellore-Khammam Schist Belt in the Khammam area were reported to be 1100 Ma. The tectonic juxtaposition between the Pakhal Supergroup and Nellore-Khammam Schist Belt was around 10001100 Ma.  相似文献   

Field Visit to the Ribeira Fold Belt, 1999     

Masaru Yoshida 《Gondwana Research》2000,3(2):275

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Application of frequency ratio,statistical index,and weights-of-evidence models and their comparison in landslide susceptibility mapping in Central Nepal Himalaya   总被引：12，自引：1，他引：11  

Amar Deep Regmi  Krishna Chandra Devkota  Kohki Yoshida  Biswajeet Pradhan  Hamid Reza Pourghasemi  Takashi Kumamoto  Aykut Akgun 《Arabian Journal of Geosciences》2014,7(2):725-742

The Mugling–Narayanghat road section falls within the Lesser Himalaya and Siwalik zones of Central Nepal Himalaya and is highly deformed by the presence of numerous faults and folds. Over the years, this road section and its surrounding area have experienced repeated landslide activities. For that reason, landslide susceptibility zonation is essential for roadside slope disaster management and for planning further development activities. The main goal of this study was to investigate the application of the frequency ratio (FR), statistical index (SI), and weights-of-evidence (WoE) approaches for landslide susceptibility mapping of this road section and its surrounding area. For this purpose, the input layers of the landslide conditioning factors were prepared in the first stage. A landslide inventory map was prepared using earlier reports, aerial photographs interpretation, and multiple field surveys. A total of 438 landslide locations were detected. Out these, 295 (67 %) landslides were randomly selected as training data for the modeling using FR, SI, and WoE models and the remaining 143 (33 %) were used for the validation purposes. The landslide conditioning factors considered for the study area are slope gradient, slope aspect, plan curvature, altitude, stream power index, topographic wetness index, lithology, land use, distance from faults, distance from rivers, and distance from highway. The results were validated using area under the curve (AUC) analysis. From the analysis, it is seen that the FR model with a success rate of 76.8 % and predictive accuracy of 75.4 % performs better than WoE (success rate, 75.6 %; predictive accuracy, 74.9 %) and SI (success rate, 75.5 %; predictive accuracy, 74.6 %) models. Overall, all the models showed almost similar results. The resultant susceptibility maps can be useful for general land use planning.  相似文献   

Decrease of size of hummocks with downstream distance in the rockslide-debris avalanche deposit at Iriga volcano, Philippines: similarities with Japanese avalanches     

Hidetsugu Yoshida 《Landslides》2013,10(5):665-672

A morphometric investigation of the longitudinal distribution of hummocks at the southeastern foot of Iriga volcano in the Philippines showed that hummock size decreases away from the volcano. Aerial photographs and GIS analysis revealed that the size–distance relationship can be expressed as the exponential function A?=?α exp (?β D), where A is the area of a hummock and D is its distance from the source. This relationship is the same as that observed previously for freely spreading debris avalanches in Japan, including two avalanches at Bandai volcano. This size–distance relationship provides information about the physical characteristics of the event: the α value shows a strong correlation with the volume of the collapsed mass of the volcanic edifice, and the β value shows a strong correlation with the coefficient of friction of the debris avalanche. Thus, morphometric analysis of hummocks created by a volcanic avalanche illuminates both the physical properties of the volcanic body and the mobility of the avalanche. For the Iriga debris avalanche, the observed longitudinal hummock distribution is clearly a function of the volume of the collapsed mass and the coefficient of friction of the avalanche. The relationships so defined appear to be a geometric effect related to the areal extent of freely spreading hummocky avalanche deposits, especially their longitudinal dimensions.  相似文献   

EPMA Chemical Ages of Paleoproterozoic Granitoids in NW India and Their Significance     

S. Biju-Sekhar  K. Yokoyama  M. Santosh  M.K. Pandit  T. Okudaira  M. Yoshida 《Gondwana Research》2001,4(4):577-578

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Pan-African Extensional Collapse Along the Gondwana Suture     

M. Santosh  M. Yoshida 《Gondwana Research》2001,4(2)

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Crustal Evolution in South and Southeast Asia: Introduction     

S. Hada  M. Yoshida  Z.X. Li  X. Wang 《Gondwana Research》2001,4(1)

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Non-local memory effects of the electromotive force by fluid motion with helicity and two-dimensional periodicity     

Kumiko Hori  Shigeo Yoshida 《地球物理与天体物理流体动力学》2013,107(6):601-632

In mean-field dynamo theory, the electromotive force term 〈u′ × B′〉 due to small-scale fields connects the small-scale magnetic field with the large-scale field. This term is usually approximated as the α-effect, assumed to be instantaneous in time and local in space. However, the approximation is valid only when the magnetic Reynolds number Rm is much less than unity, and is inappropriate when Rm ? 1, which is the condition satisfied in the Earth's core or solar convection zone. We introduce a function φ _qr as a non-local and non-instantaneous generalization of the usual α-effect and examine its behaviour as a function of Rm in the range 1/64 ≤ Rm ≤ 10 for a kinematic dynamo model. We use the flow of G.O. Roberts 1972 Roberts, GO. 1972. Dynamo action of fluid motions with two-dimensional periodicity. Phil. Trans. Roy. Soc. London Ser. A, 271: 411–454. [Crossref], [Web of Science ®] , [Google Scholar] (Phil, Trans. Roy. Soc. London Ser. A, 1972, 271, 411–454), which is steady and has non-zero helicities and two-dimensional periodicity. As a result, we identify three regions in Rm space according to the behaviour of the function φ _qr : (i) Rm ? 1/4, where the function φ _qr is local and instantaneous and can be approximated by the traditional α and β effects, (ii) 1/4 ? Rm ? 4, where the deviation from the traditional α and β effects increases and non-localness and non-instantaneousness increase, and (iii) Rm ? 4, where boundary layers develop fully and non-localness and non-instantaneousness are prominent. We show that the non-local memory effect for Rm ? 4 strongly affects the dynamo action and explains an observed augmentation of the growth rate in the dispersion relation. The results imply that the non-local memory effect of the electromotive force should be important in the geodynamo or the solar dynamo.  相似文献   

Distribution of nitrous oxide dissolved in water masses in the eastern subtropical North Pacific and its origin inferred from isotopomer analysis     

Ayako Fujii  Sakae Toyoda  Osamu Yoshida  Shuichi Watanabe  Ken’ichi Sasaki  Naohiro Yoshida 《Journal of Oceanography》2013,69(2):147-157

N₂O concentration and its isotopomer ratios were measured over a wide area from San Diego to Honolulu in the eastern subtropical North Pacific (ESNP). Waters in the study area had an N₂O maximum (38.2–50.5 nmol kg^?1) at 600–1000 m depth, which is similar to the profiles obtained previously in other areas in the North Pacific. We separated the seawater into five water masses (two for the surface layer, two for the middle layer, and one for the deep layer) and deduced N₂O production–consumption mechanisms in each water body by use of N₂O isotopomer ratios. The results showed that the mechanisms differ slightly among water masses. In the “coastal” surface layer, N₂O is produced by nitrification (NH₂OH oxidation). In the “open ocean” surface layer, it is produced mainly by nitrifier denitrification and to a lesser extent by nitrification under substrate-limited conditions. In both “upwelling” and “open ocean” middle layers it is produced mainly by denitrification and to a lesser extent by nitrifier denitrification. It is also partly reduced. In the deep layer, it is produced predominantly by denitrification with partial reduction. In this way, isotopomers aid elucidation of production–consumption mechanisms of N₂O in the sea even though the mechanisms cannot always be ascertained.  相似文献