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61.
We have measured helium isotopic ratios of thirty-seven Pacific water samples from various depths collected in adjacent regions
of Honshu, Japan. The 3He/4He ratios vary significantly from 0.989 R
atm to 1.208 R
atm where R
atm is the atmospheric ratio of 1.39 × 10−6. The mid-depth (750–1500 m) profile of 3He/4He ratios at ST-1 located Northwestern Pacific Ocean east of Japan (Off Joban; 37°00′ N, 142°40′ E) is significantly different
from that at ST-2 of the Northern Philippine Sea south of Japan (Nankai Trough; 33°07′ N, 139°59′ E), suggesting that these
waters were separated by a topographic barrier, the Izu-Ogasawara Ridge. Taking 3He/4He data of the Geosecs expeditions in the western North Pacific, an extensive plume of 15% excess 3He relative to the air may be traced at ST-1 over 12,000 kilometers to the northwest of the East Pacific Rise where the mantle
helium may originate. The 20% excess found at ST-2 may be attributable to the additional source of the subduction-type mantle
helium in the Okinawa Trough. A 15% excess of 3He has also been discovered at a depth of about 1000∼1500 m at ST-3 adjacent to Miyakejima Island (33°57′ N, 139°22′ E) and
ST-4 of Sagami Bay (35°00′ N, 139°22′ E). It is confirmed that mid-depth all over the western North Pacific water is affected
by the mantle helium with a high 3He/4He ratio.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
62.
Yasushi Fukamachi Kay I. Ohshima Naoto Ebuchi Tadao Bando Kazuya Ono Minoru Sano 《Journal of Oceanography》2010,66(5):685-696
Time-series data of the vertical structure of the Soya Warm Current (SWC) were obtained by a bottom-mounted acoustic Doppler
current profiler (ADCP) in the middle of the Soya Strait from September 2006 to July 2008. The site of the ADCP measurement
was within the coverage of the ocean-radar measurement around the strait. The volume transport of the SWC through the strait
is estimated on the basis of both the vertical structure observed by the ADCP and the horizontal structure observed by the
radars for the first time. The annual transport estimates are 0.62–0.67 Sv (1 Sv = 106 m3s−1). They are somewhat smaller than the difference between the previous estimates of the inflow and outflow through other straits
in the Sea of Japan, and smaller than those obtained in the region downstream of the strait during 2004–05 (0.94–1.04 Sv).
The difference in the two periods may be attributed to interannual variability of the SWC and/or the different measurement
locations. 相似文献
63.
Decay model for biocide treatment of unballasted vessels: application for the Laurentian Great Lakes
A biocide decay model was developed to assess the potential efficacy and environmental impacts associated with using glutaraldehyde to treat unballasted overseas vessels trading on the Laurentian Great Lakes. The results of Monte Carlo simulations indicate that effective glutaraldehyde concentrations can be maintained for the duration of a vessel's oceanic transit (approximately 9-12 days): During this transit, glutaraldehyde concentrations were predicted to decrease by approximately 10% from initial treatment levels (e.g., 500 mgL(-1)). In terms of environmental impacts, mean glutaraldehyde concentrations released at Duluth-Superior Harbor, MN were predicted to be 100-fold lower than initial treatment concentrations, and ranged from 3.2 mgL(-1) (2 SD: 2.74) in April to 0.7 mgL(-1) (2 SD: 1.28) in August. Sensitivity analyses indicated that the re-ballasting dilution factor was the major variable governing final glutaraldehyde concentrations; however, lake surface temperatures became increasingly important during the warmer summer months. 相似文献
64.
The KASMMER (Kakioka Automatic Standard Magnetometer) has been constructed in 1972 for the standard magnetic observation at Kakioka (Yanagiharaet al., 1973). Then KASMMER system has been improved successively for the high level standard magnetic observation. The purpose of the present paper is to introduce an outline of the improved KASMMER system.The KASMMER system consists of four parts which are four optical pumping magnetometers, a fluxgate magnetometer (Supporting system to the optical pumping magnetometers), a calibration system and a data acquisition system (computer system). The calibration system consists of a proton magnetometer and a magnetic theodolite (Di-72). Details for each part are described and the ability of the improved system is shown to be higher than that of classical magnetic observatory systems. 相似文献
65.
66.
Keika Horiguchi Sadato Ueki Yuji Sano Naoto Takahata Akira Hasegawa George Igarashi 《Island Arc》2010,19(1):60-70
In order to study the precise geographical distribution of helium isotope ratios in northeastern Japan and compare it with geophysical data, we collected 43 gas and water samples from hot and mineral springs in the region where the ratio had never been reported, and measured the 3 He/4 He and 4 He/20 Ne ratios of these samples. It was found that the 3 He/4 He ratios show clear contrasts between the forearc and the back-arc regions in the Tohoku district in northeastern Japan. In the forearc region, the ratios are smaller than 1 RA (1 RA = 1.4 × 10−6 ; RA means the 3 He/4 He ratio of the atmosphere). On the other hand, those along the volcanic front and in the back-arc region are apparently higher. Moreover, we found a variation in the 3 He/4 He ratios along the volcanic front. In Miyagi Prefecture (38–39°N), the ratios range from 2 to 5 RA . On the other hand, the ratios are less than 1 RA in and around the southern border between Iwate and Akita Prefectures (39–39.5°N). Comparing the distribution of helium isotope ratios to results of recent geophysical studies, we found that the features in geographical distribution of helium isotope ratios are similar to those of seismic low-velocity zone distributions and high Qp−1 distributions in the uppermost mantle. These observations strongly suggest that the helium isotope ratios reflect the distribution of melts in the uppermost mantle and are a useful tool for investigating the origin, behavior, and distribution of deep fluids and melts. 相似文献
67.
68.
Yuji Sano Hiroshi Wakita Stanley N. Williams 《Journal of Volcanology and Geothermal Research》1990,42(1-2)
We have collected 14 water and gas samples from 9 thermal springs and gas vents near Nevado del Ruiz volcano, Colombia. The 3He/4He and 4He/20Ne ratios vary significantly from 0.98 Ratm (where Ratm is the atmospheric 3He/4He ratio of 1.4 × 10−6) to 6.30 Ratm, and from 0.37 to 7.0, respectively. The 3He/4He ratio (corrected for air contamination) decreases with increasing distance from the central crater of the volcano to the sampling site. The trend is very similar to that observed at Ontake volcano, Japan. A hydrodynamic porous-media dispersion model can explain the 3He/4He trend. The temporal variations in the 3He/4He ratio at four sites provide useful information on the apparent velocity of the magmatic fluid flow brought on by a volcanic eruption. The estimated value of several tens m day−1 agrees well with the inferred velocity of flow in Oshima volcano, Japan and is comparable to the largest rate of groundwater movement in a deep sedimentary basin. 相似文献
69.
Short-term and intermediate-term geochemical precursors 总被引:2,自引:0,他引:2
Detection of precursory phenomena in observation data is essential to earthquake prediction studies. Continuous monitoring of radon concentration in groundwater in Japan in one case showed a short-term anomaly related to a nearby earthquake. With the exception of the 1978 Izu-Oshimakinkai earthquake (M7.0), however, no abnormal change has been noted. This may be due partially to difficulty in detecting insignificant precursory signals from observation data, which ordinarily contains a noise-induced fluctuations, and partially to lack of understanding of the mechanism controlling the appearance of precursory phenomena. In order to increase our knowledge of the variation pattern of precursory changes in radon concentration of groundwater, hydrologic precursors with significant features are examined in this paper. Complexity of appearance of precursory phenomena and problems in assignment of the specific earthquake are discussed. 相似文献
70.
Yuji Sano Kentaro Terada Setsuo Takeno Lawrence a. Taylor Harry y. Mcsween 《Meteoritics & planetary science》2000,35(2):341-346
Abstract— We report ion microprobe U‐Th‐Pb dating of Shergotty phosphates by means of the sensitive high‐resolution ion microprobe (SHRIMP) recently installed at Hiroshima University, Japan. ten analyses of whitlockite (merrillite) and three analyses of apatite indicate a 238u/206pb isochron age of 225 ± 200 ma and a tera‐wasserburg concordia‐constrained linear three‐dimensional isochron age of 217 ± 110 ma in the 238u/206pb‐207pb/206pb204pb/206pb diagram. These ages agree well with the 232Th‐208pb age of 189 ± 83 Ma, which suggests that primary crystallization or a shock metamorphic event defined the formation age of the phosphate minerals. The average of the later two ages, 204 ± 68 Ma, is consistent with the previously published Rb‐Sr age of 165 ± 11 Ma and U‐Th‐Pb age of ~200 Ma. These show marginal agreement with the 40Ar‐39Ar age of 254 ± 10 Ma but are significantly different from the Sm‐Nd age of 360 ± 16 Ma. Taking into account the closure temperature of the U‐Pb system in apatite, we suggest the time that Shergotty last experienced a temperature of ~900 °C was 204 ± 68 Ma. 相似文献