Outflow of the Intermediate Oyashio Water from Sagami Bay to the Shikoku Basin     

Yoshihiko Sekine  Keita Uchiyama 《Journal of Oceanography》2002,58(4):531-537

Since the Intermediate Oyashio Water (IOW) gradually accumulates in Sagami Bay, it can reasonably be supposed that the IOW also flows out from Sagami Bay, even though it may be altered by mixing with other waters. We have occasionally observed a water less than 34.2 psu with a potential density of 26.8 at the southeastern area off Izu Peninsula in July 1993 by the training vessel Seisui-maru of Mie University. Observational data supplied by the Japan Meteorological Agency and the Kanagawa Prefectural Fisheries Experimental Station show that the IOW of less than 34.1 psu was observed at northern stations of the line PT (KJ) off the Boso Peninsula and to the east of Oshima in the late spring 1993. Based upon these observations, it is concluded that the IOW flows out from Sagami Bay into the Shikoku Basin along southeastern area off the Izu Peninsula. The less saline water (<34.2 psu) was also observed to the west of Miyake-jima during the same cruise, and the westward intrusion of IOW from south of the Boso Peninsula to the Shikoku Basin through the gate area of the Kuroshio path over the Izu Ridge was detected. This event indicated that the IOW branched south of the Boso Peninsula and flowed into Sagami Bay and/or into the gate area over the Izu Ridge. The southward intrusion of IOW into the south of the Boso Peninsula is discussed in relation to the latitudinal location of the main axes of the Kuroshio and the Oyashio. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

The distribution of Fe3+ and Ga3+ between two tetrahedral sites in melilites,Ca2(Mg,Fe3+, Ga,Si)3O7     

Masahide Akasaka  Haruo Ohashi  Isamu Shinno 《Physics and Chemistry of Minerals》1986,13(3):152-155

The distribution of Fe³⁺ and Ga³⁺ between the two tetrahedral sites in three synthetic melilites has been studied by using ⁵⁷Fe Mössbauer spectroscopy. In the melilite, (Ca₂Ga₂SiO₇)₅₀ (Ca₂Fe³⁺GaSiO₇)₅₀ (mol %), the distribution of Fe³⁺ and Ga³⁺ in T1 and T2 sites is apparently random, which can be explained in terms of the electrostatic valence rule. However in the melilites, (Ca₂MgSi₂O₇)₅₂ (Ca₂Fe³⁺GaSiO₇)₄₂ (Ca₂Ga₂SiO₇)₆ and (Ca₂MgSi₂O₇)₆₂ (Ca₂Fe³⁺GaSiO₇)₃₆ (Ca₂Ga₂SiO₇)₂ (mol %), Fe³⁺ shows preference for the more ionic T1 site and Ga³⁺ for the more covalent T2 site. If the electronegativity of Ga³⁺ is assumed to be larger than that of Fe³⁺, the mode of distribution of Fe³⁺ and Ga³⁺ can be explained in terms of our previous hypothesis that a large electronegativity induces a stronger preference for the more covalent T2 site.  相似文献   

Probabilistic aspects of micropaleontologic assemblage zones     

Isamu Hattori 《Mathematical Geology》1985,17(2):167-175

A micropaleontologic assemblage zone is defined by occurrence of some characteristic species among many coeval species. When number of assemblage-defining species and total number of species observed are designated as Aand N,respectively, the ratio, A/N,is strongly dependent on duration of the assemblage. Theoretical consideration on the basis of a micropaleontologic cohort model shows that, when origination rate and extinction rate of species are obtained, the most reasonable ratio (A/N) and duration of the assemblage can be determined. The probabilistic model described in this paper provides a theoretical relation between the ratio and the duration. Inaccuracy in correlating micropaleontologic data to certain assemblage zones established can not be avoided because of many natural sorting and artificial biases. Ambiguity arising when data with a small number of characteristic species are correlated with a certain assemblage is numerically estimated.  相似文献   

Current Nature of the Kuroshio in the Vicinity of the Kii Peninsula   总被引：1，自引：0，他引：1  

Yutaka Nagata  Junichi Takeuchi  Makoto Uchida  Isamu Ishikura  Yoshitaka Morikawa  Takashi Koike 《Journal of Oceanography》1999,55(3):407-416

The Kuroshio flows very close to Cape Shionomisaki when it takes a straight path. The detailed observations of the Kuroshio were made both on board the R/V Seisui-maru of Mie University and on board the R/V Wakayama of the Wakayama Prefectural Fisheries Experimental Station on June 11–14, 1996. It was confirmed that the current zone of the Kuroshio touches the coast and bottom slope just off Cape Shionomiaki, and that the coastal water to the east of the cape was completely separated from that to the west. The relatively high sea level difference between Kushimoto and Uragami could be caused by this separation of the coastal waters when the Kuroshio takes a straight path. This flow is rather curious, as the geostrophic flow, which has a barotropic nature and touches the bottom, would be constrained to follow bottom contours due to the vorticity conservation law. The reason why the Kuroshio leaves the bottom slope to the east of Cape Shionomisaki is attributed to the high curvature of the bottom contours there: if the current were to follow the contours, the centrifugal term in the equation of motion would become large and comparablee to the Coriolis (or pressure gradient) term, and the geostrophic balance would be destroyed. This creates a current-shadow zone just to the east of the cape. As the reason why the current zone of the Kuroshio intrudes into the coastal region to the west of the cape, it is suggested that the Kii Bifurcation Current off the southwest coast of the Kii Peninsula, which is usually found when the Kuroshio takes the straight path, has the effect of drawing the Kuroshio water into the coastal region. The sea level difference between Kushimoto and Uragami is often used to monitor the flow pattern of the Kuroshio near the Kii Peninsula. It should be noted that Uragami is located in the current shadow zone, while Kushimoto lies in the region where the offshore Kuroshio water intrudes into the coastal region. The resulting large sea level difference indicates that the Kuroshio is flowing along the straight path.  相似文献   

Effect of bedrock flow on catchment rainfall‐runoff characteristics and the water balance in forested catchments in Tanzawa Mountains,Japan     

Tomoki Oda  Masakazu Suzuki  Tomohiro Egusa  Yoshimi Uchiyama 《水文研究》2013,27(26):3864-3872

In this paper, we examined the role of bedrock groundwater discharge and recharge on the water balance and runoff characteristics in forested headwater catchments. Using rigorous observations of catchment precipitation, discharge and streamwater chemistry, we quantified net bedrock flow rates and contributions to streamwater runoff and the water balance in three forested catchments (second‐order to third‐order catchments) underlain by uniform bedrock in Japan. We found that annual rainfall in 2010 was 3130 mm. In the same period, annual discharge in the three catchments varied from 1800 to 3900 mm/year. Annual net bedrock flow rates estimated by the chloride mass balance method at each catchment ranged from ?1600 to 700 mm/year. The net bedrock flow rates were substantially different in the second‐order and third‐order catchments. During baseflow, discharge from the three catchments was significantly different; conversely, peak flows during large storm events and direct runoff ratios were not significantly different. These results suggest that differences in baseflow discharge rates, which are affected by bedrock flow and intercatchment groundwater transfer, result in the differences in water balance among the catchments. This study also suggests that in these second‐order to third‐order catchments, the drainage area during baseflow varies because of differences between the bedrock drainage area and surface drainage area, but that the effective drainage area during storm flow approaches the surface drainage area. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

X-ray observations of PSR B1259−63 near the 2007 periastron passage     

M. Chernyakova  A. Neronov  F. Aharonian  Y. Uchiyama  T. Takahashi 《Monthly notices of the Royal Astronomical Society》2009,397(4):2123-2132

PSR B1259−63 is a 48-ms radio pulsar in a highly eccentric 3.4-yr orbit with a Be star SS 2883. Unpulsed γ-ray, X-ray and radio emission components are observed from the binary system. It is likely that the collision of the pulsar wind with the anisotropic wind of the Be star plays a crucial role in the generation of the observed non-thermal emission. The 2007 periastron passage was observed in unprecedented details with Suzaku , Swift , XMM–Newton and Chandra missions. We present here the results of this campaign and compare them with previous observations. With these data we are able, for the first time, to study the details of the spectral evolution of the source over a 2-month period of the passage of the pulsar close to the Be star. New data confirm the pre-periastron spectral hardening, with the photon index reaching a value smaller than 1.5, observed during a local flux minimum. If the observed X-ray emission is due to the inverse Compton (IC) losses of the 10-MeV electrons, then such a hard spectrum can be a result of Coulomb losses, or can be related to the existence of the low-energy cut-off in the electron spectrum. Alternatively, if the X-ray emission is a synchrotron emission of very high-energy electrons, the observed hard spectrum can be explained if the high-energy electrons are cooled by IC emission in Klein–Nishina regime. Unfortunately, the lack of simultaneous data in the TeV energy band prevents us from making a definite conclusion on the nature of the observed spectral hardening and, therefore, on the origin of the X-ray emission.  相似文献   

Oblique and near collision subduction, Sagami and Suruga Troughs —preliminary results of the French-Japanese 1984 Kaiko cruise, Leg 2     

Kazuaki Nakamura  Vincent Renard  Jacques Angelier  Jacques Azema  Jacques Bourgois  Christine Deplus  Kantaro Fujioka  Yozo Hamano  Philippe Huchon  Hajimu Kinoshita  Pierre Labaume  Yujiro Ogawa  Tetsuzo Seno  Akira Takeuchi  Manabu Tanahashi  Akinori Uchiyama  Jean-Louis Vigneresse 《Earth and Planetary Science Letters》1987,83(1-4)

Leg 2 of the French-Japanese 1984 Kaiko cruise has surveyed the Suruga and the Sagami Troughs, which lie on both sides of the northwestward moving and colliding Izu-Bonin Ridge, the northernmost part of the Philippine Sea plate. The transition from the Nankai Trough to the Suruga Trough is characterized by northward decrease in width of the accretionary prism, in good agreement with the increasing obliquity between the through axis and the direction of the convergence, as the strike of the convergent boundary changes from ENE-NNE to south-north. South of the area, the southern margin of the Zenisu Ridge shows contractional deformations. This supports the interpretation made by the team of Leg 1 who studied the western extension of the area we studied, that it is an intra-oceanic thrusting of the ridge over the Shikoku Basin. In the Sagami Trough, where the relative motion is highly oblique to the plate boundary, active subduction is mostly confined in the east-west trending portions of the trough located south of the Boso Peninsula and along the lower Boso Canyon, near the TTT triple junction. In between, the present motion is mainly right-lateral along the northwest trending Boso escarpment. However, an inactive but recent (Pliocene to lower Pleistocene) accretionary prism exists south of the Boso escarpment, which suggests that the relative motion was more northerly than at present before about 1 Ma ago.  相似文献   

A study of the groundwater cycle in Sri Lanka using stable isotopes     

Xianfang Song  Isamu Kayane  Tadashi Tanaka  Jun Shimada 《水文研究》1999,13(10):1479-1496

The characteristics of the groundwater cycle were researched using stable isotope technology in western Sri Lanka where climatic conditions change greatly within a relatively short distance. The effects of local climate, surface water and topography on the groundwater cycle in the study area with similar geological conditions were investigated. Sri Lanka can be divided spatially into a dry zone, an intermediate zone and a wet zone, and also temporally into the rainy season and the dry season. The zonal characteristics of the groundwater cycle were also elucidated using stable isotopic technology. As an input δ diagram of precipitation in the study area, there are obvious seasonal changes in the isotopic composition and a magnitude effect, both in the wet zone and dry zone. In the wet zone, the slope of the regression line between δ D and δ ¹⁸O and deuterium excess is close to 8 and 10, respectively. However, in the dry zone, the slope of the regression line between δ D and δ ¹⁸O and deuterium excess is much less than 8 and 10, respectively. In the wet zone, there is an obvious seasonal change in the isotopic composition of groundwater. The groundwater was recharged by precipitation during the whole year. The isotopically lighter groundwater was found at the valley bottom in the rainy season there. Under the very heavy precipitation conditions, the slope of the regression line between δ D and δ ¹⁸O and deuterium excess for groundwater was close to 8 and 10, respectively. In other cases, the slopes of the regression lines are less than 8. In the dry zone, the groundwater was recharged by precipitation only in the rainy season. The isotopically lighter groundwater was found on the ridge of the valley in the rainy season. The slope of the regression line between δ D and δ ¹⁸O and deuterium excess for groundwater was much less than 8 and 10, respectively. Copyright © 1999 John Wiley & Sons, Ltd.  相似文献   

Long-period waves in the vicinity of Onagawa Bay (I)     

Isamu Aida  Tokutaro Hatori  Morio Koyama  Hideki Nagashima  Kinjiro Kajiura 《Journal of Oceanography》1972,28(5):207-219

To investigate the response characteristics of a bay to tsunamis, field measurements of long-period waves have been carried out at Onagawa and Okachi Bays, both of which face the Pacific Ocean in northern Japan. In Onagawa Bay, the observed transfer function is in good agreement with the prediction based on the one-dimensional numerical model, in the period range larger than about 15 minutes. The response of shorter periods seems to be influenced by the two-dimensionality of the bay. The oscillations within Onagawa Harbor are also discussed with respect to the relative amplitude and phase at two stations inside the harbor and it is estimated that the reflection coefficient at the waterfront is about 0.7. In Okachi Bay, the oscillations in the period range larger than about 10 minutes could be explained by a Y-shaped model of the bay. The dominant oscillations offshore of these two-bays are found to be the mode with the motion predominantly in the direction normal to the shelf orientation, and the estimated power spectral density of incoming waves in deep water varies asf ^–2,f being the frequency. The waves of lateral modes, such as edge waves on the shelf, are small and of minor importance to generate bay oscillations of longer periods.  相似文献   

How do “numbers” construct social reality in disaster-stricken areas?: a case of the 2008 Wenchuan earthquake in Sichuan,China     

Seiji Kondo  Katsuya Yamori  Tomohide Atsumi  Isamu Suzuki 《Natural Hazards》2012,62(1):71-81

This article focuses on the dynamics of using numbers to construct an image of social reality in disaster areas. Numbers are neither objective nor value-neutral but are rather generated, transmitted and shared with social signification. In other words, numbers can be thought of as simply socially constructed information. Statistics and other numbers usually work in positive ways. However, it is also possible that using numbers in the media can lead to unintended messages that could produce negative consequences. We conducted field studies in disaster-stricken areas of the 2008 Wenchuan earthquake in China and compared findings to the case of the 1995 Kobe earthquake in Japan in order to examine how numbers—in terms of the amount of donations, the timeline of reconstruction projects and casualty figures—construct social reality and cause a variety of social dysfunctions.  相似文献