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排序方式: 共有138条查询结果,搜索用时 31 毫秒
11.
ResearchontheseismotectonicsoftheJan┐uary17,1995HanshinM7.2earthquakeZHU-JUNHAN1)(韩竹君),FU-HUREN2)(任伏虎),YujiroOgawa2)(小川雄二郎)a... 相似文献
12.
13.
Shinya Iwasaki Kozo Takahashi Yusuke Ogawa Seiichiro Uehara Christoph Vogt 《Journal of Oceanography》2014,70(3):241-249
Accurate knowledge of the extent of biogenic opal preservation in marine sediment cores is important for paleoceanographic reconstructions. The alkaline leaching method is widely employed for %biogenic opal analysis due to its ease and speed. In this study, a revised method for measuring %biogenic opal in sediment from arctic coring expedition samples was suggested. The studied middle Eocene sediments from the central Arctic Ocean presented a problem in insufficiently leaching biogenic opal with a Na2CO3 solution. Based on XRD analysis, it was suggested that such an alkaline resistance results from slight diagenesis of biogenic opal. In order to solve this problem, an alkaline leaching method utilizing a 2 M NaOH solution was suggested for the accurate measurement of %biogenic opal in the Eocene sediments from the central Arctic. Furthermore, dissolution rates from lithogenic matter by NaOH solution were measured in order to correct the %biogenic opal values. 相似文献
14.
Ablation processes of snow under a thin dust cover are complicated compared with those under a thick cover, mainly owing to the effects of aggregation (redistribution) of dust particles on the conditions of surface melting. Aggregation of dust particles causes the snow surface to brighten after the initial dust configuration, thus affecting the relationship between initial dust concentration and surface albedo. In order to estimate snow ablation rate under a thin dust cover, we used a composite energy balance model in which the surface albedo is taken as a measured input variable. The estimated results of snow ablation agreed reasonably well with the observation, considering the measurement errors inherited in the snow depressions. Comparison of the two cases, that is, one considering the aggregation of dust particles (observation: albedo variable) and the other without aggregation (assumption: albedo constant), showed that the ablation rates were noticeably lower on the former case. This suggests that the aggregation of dust particles induces a reduction of snow ablation. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
15.
Yujiro Ogawa Ryota Mori Toshiaki Tsunogae Yildirim Dilek Ron Harris 《International Geology Review》2015,57(5-8):824-842
Many concepts and interpretations on the formation of the Franciscan mélange have been proposed on the basis of exposures at San Simeon, California. In this paper, we show the distribution of chaotic rocks, their internal structures and textures, and the interrelationship between the chaotic rocks and the surrounding sandstones (turbidites). Mélange components, particularly blueschists, oceanic rocks, including greenstone, pillow lava, bedded chert, limestone, sandstone, and conglomerate, have all been brecciated by retrograde deformation. The Cambria Slab, long interpreted as a trench slope basin, is also strongly deformed by fluidization, brecciation, isoclinal folding, and thrusting, leading us to a new interpretation that turbiditic rocks (including the Cambria Slab) represent trench deposits rather than slope basin sediments. These rocks form an accretionary prism above mélanges that were diapirically emplaced into these rocks first along sinistral-thrust faults, and then along dextral-normal faults. Riedel shear systems are observed in several orders of scale in both stages. Although the exhumation of the blueschist blocks is still controversial, the common extensional fractures and brecciation in most of the blocks in the mélanges and further mixture of various lithologies into one block with mélange muddy matrix indicate that once deeply buried blocks were exhumed from considerable depths to the accretionary prism body, before being diapirically intruded with their host mélange along thrust and normal faults, during which retrograde deformation occurred together with retrograde metamorphism. Recent similar examples of high-pressure rock exhumation have been documented along the Sofugan Tectonic Line in the Izu forearc areas, in the Mineoka belt in the Boso Peninsula, and as part of accretionary prism development in the Nankai and Sagami troughs of Japan. These modern analogues provide actively forming examples of the lithological and deformational features that characterize the Franciscan mélange processes. 相似文献
16.
We studied the relationships between streamwater chemistry and the topography of subcatchments in the Dorokawa watershed in Hokkaido Island, northern Japan, to examine the use of topography as a predictor of streamwater chemistry in a watershed with relatively moderate terrain compared with other regions of Japan. Topographic characteristics of the Dorokawa watershed and its subcatchments were expressed as topographic index (TI) values, which ranged from 4·5 to 20·4 for individual grid cells (50 × 50 m2), but averaged from 6·4 to 7·4 for the 20 subcatchments. Streamwater samples for chemical analyses were collected four times between June and October 2002 from 20 locations in the watershed. The pH of water that passed through the watershed increased from ~5·0 to 7·0, with major increases in Na+ and Ca2+ and marked decreases in NO3? and SO . Distinctive spatial patterns were observed for dissolved organic carbon (DOC), dissolved organic nitrogen (DON), and NO3? concentrations of streamwater across the watershed. Statistical analyses indicated significant linear relationships between the average TI values of subcatchments and DOC, DON, and NO3? concentrations. Furthermore, the proportion of DOC in streamwaters in the wet season increased with TI values relative to other nitrogen species, whereas NO3? concentrations decreased with TI. The gradients of soil wetness and the presence of wetlands explained many of the observed spatial and temporal patterns of DOC, DON, and NO3? concentrations in the surface waters of the Dorokawa watershed. Our results suggest that the TI is especially useful for predicting the spatial distribution of DOC, DON and NO3? in the surface waters of Hokkaido, where topographical relief is moderate and wetlands more common than in other regions of Japan. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
17.
Sediment organic matter source estimation and ecological classification in the semi-enclosed Batan Bay Estuary,Philippines 总被引:2,自引:0,他引:2
The large organic matter flow in tropical coastal areas is recognized as an important process in the global carbon(C)cycle.However,the nature of organic matter flow in semi-enclosed tropical estuaries remains unclear due to the various environmental processes(tidal change,river flow,waves from the sea,and internal circulation)and organic matter sources therein.Thus,sediment organic matter(SOM)sources,and their distribution pattern,are key to understanding ecosystem material flow.Our research in the Batan Bay Estuary,Philippines,a semi-enclosed estuary under large mangrove deforestation,was conducted to determine ecosystem properties through analysis of C and nitrogen stable isotope ratios and environmental factors.First,we determined that mangrove litter,microphytobenthos,and phytoplankton are the main SOM sources in the Batan Bay Estuary.Second,the estuary was classified into three ecological zones(the Bay zone,Back-barrier zone,and River zone).In addition,we estimated SOM source ratios using the Stable Isotope Analysis in R package and determined different organic matter sources in different zone.The high ratios of mangrove litter as SOM indicate that a large amount of terrestrial plant organic matter remains despite the heavy mangrove deforestation that has occurred since the 1980s,and that the Back-barrier zone consists of a different type of ecosystem that promotes accumulation of C from mangrove litter and microphytobenthos. 相似文献
18.
Long-Term Variations of Potential Temperature and Dissolved Oxygen of the Japan Sea Proper Water 总被引:4,自引:0,他引:4
Observed potential temperatures and concentrations of dissolved oxygen are analyzed to elucidate their variations during the
period from 1958 to 1996 at Stn. P (37°43′ N, 134°43′ E) and from 1965 to 1996 at Stn. H (40°30′ N, 137°40′ E) in the Japan
Sea. At Stn. P, increases of the potential temperature for the period are found below 800 m depth with the largest value of
0.16 ± 0.09°C per century at 800 m depth. At Stn. H, the potential temperature increased below 500 m depth. The increase rate
has the largest value of 0.50 ± 0.18°C per century at 500 m depth and it is 0.30 ± 0.09°C per century at 800 m depth. The
concentrations of dissolved oxygen increased around 800 m depth at Stn. P. At Stn. H, they increased above 800 m depth. On
the other hand, they decreased below 1200 m depth at both stations. The layer of the dissolved oxygen minimum has deepened
in these decades. These features appearing in the distributions of temperature and dissolved oxygen are successively simulated
by a vertical one-dimensional advection-diffusion model including consumption of dissolved oxygen and termination of the deep
water supply. These results suggest that the supply of the Japan Sea Proper Water into the deep layer, which is cold and rich
in dissolved oxygen, has been decreasing for the last four decades.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
19.
Mohammad Rezwanul Islam Syeda Fahliza Begum Yasushi Yamaguchi Katsuro Ogawa 《水文研究》1999,13(17):2907-2923
Every year the Ganges and Brahmaputra rivers in Bangladesh transport 316 and 721 million tonnes of sediment, respectively. These high loads of suspended sediment reflect the very high rate of denudation in their drainage basins. The average mechanical denudation rate for the Ganges and Brahmaputra basins together is 365 mm 103 yr−1. However, the rate is higher in the Brahmaputra Basin than that in the Ganges Basin. Several factors, including mean trunk channel gradient, relief ratio, runoff, basin lithology and recurring earthquakes are responsible for these high denudation rates. Of the total suspended sediment load (i.e. 1037 million tonnes) transported by these rivers, only 525 million tonnes (c. 51% of the total load) are delivered to the coastal area of Bangladesh and the remaining 512 million tonnes are deposited within the lower basin, offsetting the subsidence. Of the deposited load, about 289 million tonnes (about 28% of the total load) are deposited on the floodplains of these rivers. The remaining 223 million tonnes (about 21% of the total load) are deposited within the river channels, resulting in aggradation of the channel bed at an average rate of about 3·9 cm yr−1. Although the Brahmaputra transports a higher sediment load than the Ganges, the channel bed aggradation rate is much higher for the Ganges. This study also documents a wide range of interannual, seasonal and daily variation in suspended sediment transport and water discharge. Interannual variation in sediment deposition within the basin is also suggested. Copyright © 1999 John Wiley & Sons, Ltd. 相似文献
20.
Toward seamless indoor-outdoor applications: Developing stakeholder-oriented location-based services
Kohei Ogawa Edward Verbree Sisi Zlatanova Naohiko Kohtake Yoshiaki Ohkami 《地球空间信息科学学报》2013,16(2):109-118
Location-Based Services (LBS), an emerging new business based on smartphone and mobile networks, are becoming more and more popular. Most of these LBSs, however, only offer non-seamless indoor/outdoor applications and simple applications without giving stakeholders the chance to play an active role. Our specific aim is to solve these issues. This paper presents concepts to solve these issues by expanding the Open Location Services Interface Standard (OpenLS) to allow seamless indoor/outdoor positioning and to extend the content of the services to include information recommended by stakeholders. 相似文献