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41.
Koichiro Doi Hideaki Hayakawa Takahito Kazama Toshihiro Higashi Shingo Osono Yoichi Fukuda Jun Nishijima Yuichi Aoyama Junichi Ueda 《极地研究(英文版)》2013,(4):339-343
Abstract This paper reports the results of field-based absolute gravity measurements aimed at detecting gravity change and crustal displacement caused by glacial isostatic adjustment. The project was initiated within the framework of the 53rd Japanese Antarctic Research Expedition (JARE53). Absolute gravity measurements, together with GPS measurements, were planned at several outcrops along the Prince Olav Coast and S6ya Coast of East Antarctica, including at Syowa Station. Since the icebreaker Shirase (AGB 5003) was unable to moor alongside Syowa Station, operations were somewhat restricted during JARE53. However, despite this setback, we were able to complete measurements at two sites: Syowa Station and Langhovde. The absolute gravity value at the Syowa Station IAGBN (A) site, observed using an FG-5 absolute gravimeter (serial number 210; FG-5 #210), was 982 524 322.7+0.1 ktGal, and the gravity change rate at the beginning of 2012 was -0.26 gGal.a-1. An absolute gravity value of 982 535 584.2~0.7 ktGal was obtained using a portable A-10 absolute gravimeter (serial number 017; A-10 #017) at the newly located site AGS01 in Langhovde. 相似文献
42.
Norihisa Usui Tsuyoshi Wakamatsu Yusuke Tanaka Nariaki Hirose Takahiro Toyoda Shiro Nishikawa Yosuke Fujii Yasushi Takatsuki Hiromichi Igarashi Haruka Nishikawa Yoichi Ishikawa Tsurane Kuragano Masafumi Kamachi 《Journal of Oceanography》2017,73(2):205-233
We produced a four-dimensional variational ocean re-analysis for the Western North Pacific over 30 years (FORA-WNP30). It is the first-ever dataset covering the western North Pacific over 3 decades at eddy-resolving resolution. The four-dimensional variational analysis scheme version of the Meteorological Research Institute Multivariate Ocean Variational Estimation system (MOVE-4DVAR) is employed to conduct a long-term reanalysis experiment during 1982–2012. After evaluating the basic performance of FORA-WNP30, the interannual to decadal variability is analyzed. Overall, FORA-WNP30 reproduces basic features in the western North Pacific well. One of outstanding features in FORA-WNP30 is that anomalous events such as the Kuroshio large meander and anomalous intrusion of the Oyashio in the 1980s, when there were no altimeter data, are successfully reproduced. FORA-WNP30 is therefore a valuable dataset for a variety of oceanographic research topics and potentially for related fields such as climate study, meteorology and fisheries. 相似文献
43.
Carbonate concretions, lenses and bands in the Pleistocene, Palaeogene and Upper Triassic coalfields of Japan consist of various carbonate minerals with varied chemical compositions. Authigenic carbonates in freshwater sediments are siderite > calcite > ankerite > dolomite >> ferroan magnesite; in brackish water to marine sediments in the coal measures, calcite > dolomite > ankerite > siderite >> ferroan magnesite; and in the overlying marine deposits, calcite > dolomite >> siderite. Most carbonates were formed progressively during burial within a range of depths between the sediment-water interface and approximately 3 km. The mineral species and the chemical composition of the carbonates are controlled primarily by the initial sedimentary facies of the host sediments and secondarily by the diagenetic evolution of pore water during burial. Based on the regular sequence and burial depth of precipitation of authigenic carbonates in a specific sedimentary facies, three diagenetic stages of carbonates are proposed. Carbonates formed during Stage I (< 500 m) strongly reflect the initial sedimentary facies, e.g. low Ca-Mg siderite in freshwater sediments which are initially rich in iron derived from lateritic soil on the nearby landmass, and Mg calcite and dolomite in brackish-marine sediments whose pore waters abound in Ca2+ and Mg2+ originating in seawater and calcareous shells. Carbonates formed during Stage II (500–2000 m) include high Ca-Mg siderite, ankerite, Fe dolomite and Fe–Mg calcite in freshwater sediments. The assemblage of Stage II carbonates in brackish-marine sediments in the coal measures is similar to that in freshwater sediments. This suggests similar diagenetic environments owing to an effective migration and mixing of pore water due to the compaction of host sediments. Carbonates formed during Stage III (> 2000 m) are Fe calcite and extremely high Ca-Mg siderite; the latter is exclusively in marine mudstones. The supply of Ca is partly from the alteration of silicates in the sediments at elevated burial temperatures. After uplift, calcite with low Mg content precipitates from percolating groundwater and fills extensional cracks. 相似文献
44.
The authors have studied alterations of Cenozoic and Mesozoic pyroclastic rocks of Japan, which contain several kinds of zeolites in abundance. This paper summarizes zeolites in sedimentary rocks, with reference to the depositional environments and zonal distribution, by a survey of the literature in addition to the authors’ data. The zonal distribution of zeolites is recognized in buried sedimentary rocks as follows: The zeolites in syngenetic or early diagenetic origin depend strongly upon a specific sedimentary environment. Phillipsite occurs largely in pelagic sediments of the younger geologic age. Analcime is found in saline-lake and terrestrial sediments in a warm, rather arid region, frequently associated with phillipsite, chabazite and natrolite. The zeolites are not influenced by the sedimentary environments but depend upon the depth of burial, i.e., increasing temperature and pressure. Most of clinop- tilolite, mordenite and erionite, forming at a relatively shallow depth, occur only as an alteration product of acidic to intermediate volcanic glass and cement of the post- Jurassic pyroclastic rocks. Laumontite, forming at a greater depth, on the other hand, is widely distributed in the pre-Pliocene various sedimentary rocks. 相似文献
45.
A 100 m laser strainmeter system installed in a 1 km deep tunnel at Kamioka, Gifu, Japan 总被引:1,自引:0,他引:1
Shuzo Takemoto Akito Araya Junpei Akamatsu Wataru Morii Hideo Momose Masatake Ohashi Ichiro Kawasaki Toshihiro Higashi Yoichi Fukuda Shinji Miyoki Takashi Uchiyama Daisuke Tatsumi Hideo Hanada Isao Naito Souichi Telada Nobuo Ichikawa Kensuke Onoue Yasuo Wada 《Journal of Geodynamics》2004,38(3-5):477
We have installed a laser strainmeter system in a deep tunnel about 1,000 m below the ground surface at Kamioka, Gifu, Japan. The system consists of three types of independent interferometers: (1) an EW linear strainmeter of the Michelson type with unequal arms, (2) an NS-EW differential strainmeter of the Michelson type with equal arms and (3) a NS absolute strainmeter of the Fabry–Perot type. These are configured in L-shaped vacuum pipes, each of which has a length of 100 m. (1) and (2) are highly sensitive (order of 10−13 strain) and have wide dynamical range (10−13–10−6). Observations with strainmeters (1) and (2) started on June 11, 2003. (3) is a new device for absolute-length measurements of the order of 10−9 of a long-baseline (100 m) Fabry–Perot cavity by the use of phase-modulated light. This third strainmeter will be ready for operation before the end of 2004. The laser source of strainmeters (1) and (2) is a frequency-doubled YAG laser with a wavelength of 532 nm. The laser frequency is locked onto an iodine absorption line and a stability of 2 × 10−13 is attained. The light paths of the laser strainmeter system are enclosed in SUS304 stainless steel pipes. The inside pressure is kept to be 10−4 Pa. Consequently, quantitative measurement of crustal strains of the order of 10−13 can be attained by employing the laser strainmeter system of (1) and (2) at Kamioka. This resolving power corresponds to that of a superconducting gravimeter. Using the laser strainmeter system, we expect to determine parameters related to fluid core resonance, core modes and core undertone as well as other geodynamic signals such as slow strain changes caused by silent earthquakes or slow earthquakes. 相似文献
46.
Piezomagnetic fields produced by dislocation sources 总被引:2,自引:1,他引:2
Yoichi Sasai 《Surveys in Geophysics》1994,15(4):363-382
Tectonomagnetic modeling based on the linear piezomagnetic effect is reviewed with special attention to dislocation models. Stacey's scheme was the prototype for such modeling, as proposed in his first seismomagnetic calculations in 1964. The linear piezomagnetic law is presented, in which the stress-induced magnetization is expressed as a linear combination of stress components. The Gauss law for magnetic field and the Cauchy-Navier equation for static elastic equilibrium are combined through linear piezomagnetism and the Hooke law to yield the basic equation for piezomagnetic potential. A representation theorem for its solution is given by surface integrals of the displacement and its normal derivative over the strained body.A Green's function method is developed to compute the piezomagnetic field produced by a dislocation surface in an elastic half-space. Volterra's formula for piezomagnetic potential is derived by modifying Stacey's scheme for tectonomagnetic modeling. The Green's functions for the problem are called elementary piezomagnetic potentials, which are defined as potentials produced by elementary dislocations. Special consideration is required to construct the elementary piezomagnetic potentials, because the stress field around a point dislocation has a singularity of orderr
–3. The integral representing elementary piezomagnetic potentials is not uniformly convergent. Owing to inappropriate convergency, the Green's functions obtained in an earlier study led to a puzzling outcome. Revised Green's functions give consistent results with those obtained so far by numerical integrations. Generally the piezomagnetic field produced by dislocation sources is weak in the case of a homogeneous earth model. Two enhancement effects for piezomagnetic signals are suggested: one due to inhomogeneous magnetization and the other via bore-hole observations. 相似文献
47.
A new species of tapejarid pterosaur, Huaxiapterus coroUatus sp. nov. is erected on the basis of a nearly complete skull and postcranial skeleton from the Lower Cretaceous Jiufotang Formation of Liaoning Province, China. Huaxiapterus coroUatus sp. nov. is characterized by a hatchet-shaped rectangular process on the premaxilla, whose short axis is perpendicular to the anterior margin of the premaxillae. Except for this process, other characters of the skull such as the breadth of the snout between the anterior margin of the nasoantorbital fenestra and the anterior margin of the premaxilla are similar to that of Huaxiapterus jii. Huaxiapterus and a second Chinese tapejarid, Sinopterus, share several unique cranial characters in common with Tapejara and these three genera appear to be more closely related to each other than to other azhdarchoids. The Chinese tapejarids (Sinopterus and Huaxiapterus) have relatively elongate skulls and weakly developed cranial crests and seem to be less derived than Tapejara, with its shorter, deeper skull and large cranial crest. Tupuxuarids (Tupuxuara and Thalassodromeus) have often been associated with tapejarids in the family Tapejaridae, but this relationship is controversial because some phylogenetic analyses have supported the pairing of tupuxuarids with Azhdarchidae. We propose that Tapejaridae be restricted to Tapejara, Sinopterus and Huaxiapterus. 相似文献
48.
Estimability analysis of variance and covariance components 总被引:1,自引:1,他引:1
Although variance and covariance components have been extensively investigated and a number of elegant formulae to compute
them have been derived, nothing is known, without any ambiguity, about their estimability in the case of a fully unknown variance–covariance
matrix. We prove that variance and covariance components in this case are not estimable, thus clarifying the ambiguity of
the literature on the topic and correcting some erroneous statements in the literature. We also give a new theorem on the
estimability of a linear function of variance and covariance components. Then we propose a new method to estimate the variance–covariance
matrix with special structure, which can presumably be represented by, at most, r(r + 1)/2 independent parameters to guarantee its estimability in such a subspace, by directly implementing the positive definiteness
of the matrix as constraint to the restricted maximum likelihood method, where r is the number of redundant measurements. Therefore, our estimates of the variance and covariance components always reconstruct
a positive definite matrix and are always physically meaningful. 相似文献
49.
Yoshifumi Nogi Kumiko Nishi Nobukazu Seama Yoichi Fukuda 《Marine Geophysical Researches》2004,25(3-4):221-231
The seafloor spreading evolution in the Southern Indian Ocean is key to understanding the initial breakup of Gondwana. We
summarize the structural lineaments deduced from the GEOSAT 10 Hz sampled raw altimetry data as well as satellite derived
gravity anomaly map and the magnetic anomaly lineation trends from vector magnetic anomalies in the West Enderby Basin, the
Southern Indian Ocean. The gravity anomaly maps by both Sandwell and Smith 1997, J. Geophys. Res. 102, 10039–10054 and 10 Hz raw altimeter data show almost the same general trends. However, curved structural trends, which turn
from NNW–SSE in the south to NNE–SSW in the north, are detected only from gravity anomaly maps by 10 Hz raw altimeter data
just to the east of Gunnerus Ridge. NNE–SSW structural trends and magnetic anomaly lineation trends that are perpendicular
to them are observed between the Gunnerus Ridge and the Conrad Rise. To the west of Gunnerus Ridge, structural elements trend
NNE–SSW and magnetic polarity changes are normal to them. In contrast, almost NNW–SSE structural trends and ENE–WSW magnetic
polarity reversal strikes are dominant to the east of Gunnerus Ridge. Curved structural trends, which turn from WNW–ESE direction
in the south to NNE–SSW direction in the west, and magnetic polarity reversal strikes that are almost perpendicular to them
are observed just south of Conrad Rise. The magnetic polarity reversals may be parts of the Mesozoic magnetic anomaly sequence
that formed along side of the structural lineaments before the long Cretaceous normal polarity superchron. Curved structural
trends, detected only from gravity anomaly maps by 10 Hz raw altimeter data, most likely indicate slight changes in spreading
direction from an initial NNW–SSE direction to NNE–SSW. Our results also suggest that these curved structural trends are fracture
zones that formed during initial breakup of Gondwana. 相似文献
50.
Wells turbine with end plates for wave energy conversion 总被引:1,自引:0,他引:1
Manabu Takao Toshiaki Setoguchi Yoichi Kinoue Kenji Kaneko 《Ocean Engineering》2007,34(11-12):1790-1795
In order to improve the performance of the Wells turbine for wave energy conversion, the effect of end plate on the turbine characteristics has been investigated experimentally by model testing. As a result, it is found that the characteristics of the Wells turbine with end plates are superior to those of the original Wells turbine, i.e., the turbine without end plate and the characteristics are dependent on the size and position of end plate. Furthermore, by using a computational fluid dynamics (CFD), reason of the performance improvement of the turbine has been clarified and the effectiveness of the end plate has been demonstrated. 相似文献