Aeromagnetic surveys of Kuttyaro and Aso caldera regions,Japan     

H. R. Blank Jr.  S. Aramaki  K. Ono 《Bulletin of Volcanology》1966,29(1):49-50

Detailed total-intensity aeromagnetic surveys of the Kuttyaro and Aso caldera regions, eastern Hokkaido and central Kyushu, were made during early 1964 under the auspices of the U.S.-Japan Co-operative Science Program in conjunction with a project for geophysical studies of calderas in Japan. Each caldera has a maximum diameter of about 22 km; the flights cover a 60 × 60 km rectangular area in each region. The Kuttyaro survey also encompasses the older caldera Akan, south-west of Kuttyaro, and the younger caldera Mashu to the east. All three lie within the Chīshīma (Kurile) volcanic zone. The isomagnetic contour map shows this zone as a belt of short wave-length anomaies which trends east-northeast across the region. Broad wavelength anomalies with trends intersecting the Chīshīma belt at an acute angle probably reflect structural relief on the Neogene volcanic basement concealed beneath Kuttyaro pyroclastic flows. The centre of Kuttyaro caldera coincides with the sharp southern termination of a strong basement high, whereas caldera faults and post-caldera domes have little magnetic expression. Mashu caldera is marked by a minimum in the position of the caldera lake; a symmetrical positive anomaly centering southeast of the caldera suggests either a buried older volcanic edifice or an intrusion. Akan caldera is represented by a magnetic depression encompassing a positive anomaly produced by its central post-caldera cone. The depression extends north of the geologically-deduced boundary of the caldera and may include an earlier collapse structure. Several volcanoes and lava sequences in the region produce negative anomalies due to inverse polarization. The most significant feature of the Aso isomagnetic map is a large, elongate positive anomaly that occupies the southern half of the caldera and extends about one caldera diameter to the south-west along the trend of the Median Tectonic Line of south-west Japan. Whether the anomaly represents the pre-Tertiary basement complex or a younger intrusion perhaps associated with Aso eruptive activity is uncertain. However, the causative body is abruptly truncated within the caldera by a major east-south-east structure passing through the eastern rim and coincident with the approximate locus of resurgent central vent eruptions. The structure may be a fault system that provided egress for the Aso pyroclastic flows. Superimposed on the basement anomaly are the effects of the topography of the caldera, the superficial caldera structure, and the post-caldera cones. An area of intense solfataric activity in the Kuju group of young volcanoes north of Aso has a pronounced negative anomaly. These two surveys illustrate the utility of the magnetic method for investigations of basement structure in caldera regions. They have served as a guide in interpreting reconnaissance aeromagnetic profiles flown concurrently for this project across some 14 other calderas or caldera-like structures in the Japanese islands.  相似文献   

网点再现与油墨流动性及纸张表面的关系     

魏先福  田中恒雄  甘利武司 《测绘学院学报》1996,(2)

分数维Ｄ值能够表示印刷网点与底片上网点的相似性关系，本文用分数维法定量评价了印刷网点的再现性，主要分析了网点再现与网屏线数、网点面积率、纸张表面粗度及油墨物性的关系。  相似文献   

Normative productivity of the global vegetation     

Georgii A Alexandrov  Tsuneo Matsunaga 《Carbon balance and management》2008,3(1):8

Background  

The biosphere models of terrestrial productivity are essential for projecting climate change and assessing mitigation and adaptation options. Many of them have been developed in connection to the International Geosphere-Biosphere Program (IGBP) that backs the work of the Intergovernmental Panel on Climate Change (IPCC). In the end of 1990s, IGBP sponsored release of a data set summarizing the model outputs and setting certain norms for estimates of terrestrial productivity. Since a number of new models and new versions of old models were developed during the past decade, these normative data require updating.  相似文献   

The 1989 submarine eruption off eastern Izu Peninsula,Japan: ejecta and eruption mechanisms     

Takahiro Yamamoto  Tatsunori Soya  Shigeru Suto  Kozo Uto  Akira Takada  Keiichi Sakaguchi  Koji Ono 《Bulletin of Volcanology》1991,53(4):301-308

The submarine eruption of a new small knoll, which was named Teishi knoll, off eastern Izu Peninsula behind the Izu-Mariana arc occurred in the evening of 13 July 1989. This is the first historic eruption of the Higashi-Izu monogenetic volcano group. The eruption of 13 July followed an earthquake swarm near Ito city starting on 30 June. There were subsequent volcanic tremors on 11 and 12 July, and the formation of the Teishi knoll on the 100 m deep insular shelf 4 km northeast of Ito city. There were five submarine explosions, which were characterized by intermittent domelike bulges of water and black tephra-jets, which occurred within 10 min on 13 July. Ejecta of the eruption was small in volume and composed of highly crystalline basalt scoria, highly vesiculated pumice, and lithic material. Petrographical features suggest that the pumice was produced by vesiculation of reheated wet felsic tuff of an older formation. The Teishi knoll, before the eruption, was a circular dome, 450 m across and 25 m high, with steep sides and a flat summit. Considerations of submarine topographic change indicate the knoll was raised by sill-like intrusion of 10⁶ m³ of magma beneath a 30 m thick sediment blanket. This shallow intrusion is assumed to have started on 11 July when volcanic tremors were observed for the first time, but there was no indications of violent interaction between wet host sediments and intruding magma. The submarine eruption of 13 July appears to have been Friggered by a major lowering of the magma-column. The basalt scoria, having crystal-contents of more than 60%, is assumed to be derived from the cooled plastic margin of the shallow intrusive body. However, glassy scoria, which would indicate the interaction between hot fluidal magma and external water, was not observed. A scenario for the 1989 submarine eruption is as follows. When rapid subsidence of the hot interior of the intrusive magma occurred, reduced pressure caused the implosion of cooled plastic magma, adjacent pressurized, hot host material, and wet sediment. The mixing of these materials triggered the vigorous vapor explosions.  相似文献   

Has the 1998 regime shift also occurred in the oceanographic conditions and lower trophic ecosystem of the Oyashio region?     

Hiromi Kasai  Tsuneo Ono 《Journal of Oceanography》2007,63(4):661-669

To examine whether the regime shift in 1998 that has been variously reported to have occurred in the oceanographic conditions of the central and eastern North Pacific also occurred in the Oyashio region, western North Pacific, we compared data over the period 1990–2003. Oceanographic conditions were compared before 1997 with those after 1998, using the A-line dataset (1990–2003) obtained by the oceanographic surveys of the Hokkaido National Fisheries Research Institute, Fisheries Research Agency (HNFRI/FRA). Seasonal changes of the monthly-mean SST (as temperature in the surface layer) show a significant increase in spring after 1998. After 1998, the mean concentration of chlorophyll a at the surface was higher in spring than that before 1997. This was more remarkable in the main current of the Oyashio. These changes suggest that the spring phytoplankton bloom in the Oyashio region after 1998 was larger in magnitude and initiated earlier. Consumption of nutrients during the spring bloom and standing stock of netplankton also shows a distinct difference between the time period before 1997 and after 1998. These results support the occurrence of the regime shift around 1998 in the Oyashio region. The changes of hydrographical conditions accompanying with the 1998 regime shift are discussed. The hydrographic mechanism of enhancement of primary productivity during the spring phytoplankton bloom was not fully clarified, though. Results in this study may support the usefulness of the A-line dataset for analysis of long-term variability in the western subarctic Pacific.  相似文献   

Seasonal fluctuations of cell density of cyanobacteria and other picophytoplankton in Iwanai Bay,Hokkaido, Japan   总被引：1，自引：0，他引：1  

Akira Miyazono  Tsuneo Odate  Yoshiaki Maita 《Journal of Oceanography》1992,48(3):257-266

In Iwanai Bay, which is located on the Japan Sea coast in Hokkaido, seasonal fluctuations in cell densities of phycoerythrin-dominant cyanobacteria and chlorophyll-dominant, other picophytoplankton were examined. Cell densities of cyanobacteria and other picophytoplankton ranged from 1.4×10⁵ to 1.9×10⁸ and from 4.0×10⁴ to 4.3×10⁶ cells 1^–1, respectively. The cell densities of both groups tended to increase after spring diatom bloom with remarkable fluctuations from June to August. This tendency was caused by the vertical distributions of both groups. The maximum density layer shifted from 0–20 m depth in April–June to 20–50 m depth in August–October. Cyanobacteria were dominant in picophytoplankton community which accounted for 73–99% of the total cell density during the whole year. Present results show that the picophytoplankton community in Iwanai Bay was influenced by a single water mass system (Tsushima Warm Current) during the whole year.This is contribution No. 254 from the Research Institute of North Pacific Fisheries, Faculty of Fisheries, Hokkaido University.  相似文献   

Re-Estimation of Annual Anthropogenic Carbon Input from Oyashio into North Pacific Intermediate Water     

Tsuneo Ono  Katsuyuki Sasaki  Ichiro Yasuda 《Journal of Oceanography》2003,59(6):883-891

The annual transport of anthropogenic carbon (C_anth) to the North Pacific Intermediate Water (NPIW) from the Western Subarctic Gyre (WSG) has been re-estimated by using newly estimated Oyashio transport and C_anth concentration, the latter calculated by the recently-established “ΔC*” method with some modifications. Estimated annual C_anth transport through the nearshore Oyashio west of 146°E was 0.020 ± 0.010 GtC y⁻¹, closely approximating the previous estimation based on a 1-D model calibrated with the CFC vertical distribution. The present study, however, found that an additional 0.025 ± 0.010 GtC y⁻¹ of C_anth was transported into NPIW in the region east of 146°E. Total C_anth transport, 0.045 GtC y⁻¹, contributes about 35% of annual C_anth accumulation of the whole temperate North Pacific. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Increased Stratification and Decreased Lower Trophic Level Productivity in the Oyashio Region of the North Pacific: A 30-Year Retrospective Study     

Sanae Chiba  Tsuneo Ono  Kazuaki Tadokoro  Takashi Midorikawa  Toshiro Saino 《Journal of Oceanography》2004,60(1):149-162

An analysis of the time series data sets collected from the 1960s to 1990s in the Oyashio Water revealed signs of alteration in the physical, chemical and biological properties of the water column in the western subarctic North Pacific. Wintertime salinity, phosphate concentration and apparent oxygen utilization (AOU) in the subsurface increased linearly over the 30 years. At the same time, salinity and phosphate in the surface mixed layer decreased. An increase in the density gradient in the surface and subsurface suggested that the water column stratification intensified, reducing the vertical exchange of water properties during the period. The Net Community Production (NCP), estimated from the phosphate consumption from February through August, also declined. Water column Chl a was approximately halved and diatoms decreased by one order of magnitude in spring, consistent with the multi-decadal decreasing trend of NCP. Zooplankton biomass was also nearly halved during the same period. In contrast, wintertime Chl a increased by 63% and diatom abundance doubled. Developmental timing became earlier in Neocalanus flemingeri, and spring occurrence of N. plumchrus increased after the 1980s. Reduced vertical water exchange might have limited nutrient supply to the level, decreasing winter-summer NCP for these three decades. It is speculated that, in the meantime, the earlier stabilization of the surface layer might have enhanced wintertime diatom production in the Oyashio's light-limited environment. This condition could allow zooplankton to effectively utilize diatoms from earlier timing, resulting in the apparent early developmental timing and abundance increase. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Mercury concentration in the ocean     

Masakichi Nishimura  Shigeki Konishi  Katsuhiko Matsunaga  Kohtaro Hata  Tsuneo Kosuga 《Journal of Oceanography》1983,39(6):295-300

Seventy percent of 342 seawater samples collected in the Bering Sea, North and South Pacific, Japan Sea, East and South China Seas, and Indian Ocean had concentrations of “total” mercury ranging from 3 to 6 ng Hg l^?1 with an arithmetic mean of 5.3 ng l^?1 and a geometric mean of 5.0 ng l^?1. In some cases, a higher concentration was observed at the surface, at the halocline or thermocline, or in the bottom water. But in general, there was no consistent correlation between mercury concentration and depth, except for a statistical tendency for mercury concentration to be slightly higher in the surface water. This tendency suggests that mercury in the ocean is supplied from the atmosphere by rain washout. The latitudinal variation of surface mercury concentrations showed that the maximum concentration at each latitude decreased from 40°N to 30°S. This variation provides evidence that atmospheric mercury is emitted mainly from continental areas naturally or anthropogenically.  相似文献   

Responses of diatoms to iron-enrichment (SEEDS) in the western subarctic Pacific, temporal and spatial comparisons     

Atsushi Tsuda  Hiroshi Kiyosawa  Akira Kuwata  Mamiko Mochizuki  Naonobu Shiga  Hiroaki Saito  Sanae Chiba  Keiri Imai  Jun Nishioka  Tsuneo Ono 《Progress in Oceanography》2005,64(2-4):189

Phytoplankton species composition was analyzed inside and outside of the iron-enriched patch during the SEEDS experiment. Before the iron-enrichment, the phytoplankton community consisted of similar proportions of pico-, nano- and micro-sized phytoplankton, and the micro-phytoplankton was dominated by the pennate diatom Pseudo-nitzschia turgidula. Although all the diatoms, except the nano-sized Fragilariopsis sp., increased during the two weeks of the observation period, the flora in the patch dramatically changed with the increase of phytoplankton biomass to a centric diatom-dominated community. Neritic diatoms, especially Chaetoceros debilis, showed higher growth rates than other diatoms, without any delay in the initiation of growth after the enrichment, and accounted for 90% of the micro-phytoplankton after day 9. In contrast, the oceanic diatoms showed distinct delays in the initiation of growth. We conclude that the responses of the diatoms to the manipulation of iron concentration were different by species, and the fast and intensive response of the phytoplankton to iron-enrichment resulted from the presence of a small amount of neritic diatoms at the study site. The important factors that determine the dominant species in the bloom are the potential growth rates under an iron-replete condition and the growth lag. Abundant species in the patch are widely distributed in the North Pacific and their relative contributions in the Oyashio area and at Stn KNOT are high from spring to summer. However, a characteristic difference of species composition between the SEEDS bloom and natural blooms was the lack of Thalassiosira and Coscinodiscus species in the patch, which usually account for a major part of the phytoplankton community under blooming conditions in the western North Pacific.  相似文献