El Niño-related sea surface elevation and ocean bottom pressure enhancement associated with the retreat of the Oyashio southeast of Hokkaido,Japan     

Hasegawa  Takuya  Nagano  Akira  Matsumoto  Hiroyuki  Ariyoshi  Keisuke  Wakita  Masahide 《Marine Geophysical Researches》2019,40(4):505-512

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Wind and buoyancy driven intermediate-layer overturning in the Sea of Okhotsk     

Junji Matsuda  Humio Mitsudera  Tomohiro Nakamura  Keisuke Uchimoto  Takuya Nakanowatari  Naoto Ebuchi 《Deep Sea Research Part I: Oceanographic Research Papers》2009,56(9):1401-1418

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Rupture process for micro-earthquakes inferred from borehole seismic recordings   总被引：1，自引：0，他引：1  

Taka’aki Taira  Douglas S. Dreger  Robert M. Nadeau 《International Journal of Earth Sciences》2015,104(6):1499-1510

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The detectability of shallow slow earthquakes by the Dense Oceanfloor Network system for Earthquakes and Tsunamis (DONET) in Tonankai district,Japan     

Keisuke Ariyoshi  Ryoko Nakata  Toru Matsuzawa  Ryota Hino  Takane Hori  Akira Hasegawa  Yoshiyuki Kaneda 《Marine Geophysical Researches》2014,35(3):295-310

In order to understand the characteristics of shallow very low-frequency (VLF) events as revealed by recent ocean-floor observation studies, we perform a trial simulation of earthquake cycles in the Tonankai district by taking the characteristics of the 1944 Tonankai earthquake and assuming that slow earthquakes occur on numerous small asperities. Our simulation results show that the increase of moment release rate of shallower VLF events in the pre-seismic stage of a megathrust earthquake is higher than that of deeper VLF events. This increase may make leveling change due to VLF swarms detectable at Dense Oceanfloor Network system for Earthquakes and Tsunamis (DONET). We also introduce the time series of hydraulic pressure data at DONET, comparing with the leveling change expected from our numerical simulation. Since leveling change due to shallower VLF swarms is so local as to be incoherent, removal of the moving-averaged data from the data stacked by four nearby observation points in the same node may be useful to detect the short-term local leveling change.  相似文献   

Cross-Validation of Open-Path and Closed-Path Eddy-Covariance Techniques for Observing Methane Fluxes     

Hiroki Iwata  Yoshiko Kosugi  Keisuke Ono  Masayoshi Mano  Ayaka Sakabe  Akira Miyata  Kenshi Takahashi 《Boundary-Layer Meteorology》2014,151(1):95-118

Methane ( ${\mathrm {CH}}_{4}$ ) fluxes observed with the eddy-covariance technique using an open-path ${\mathrm {CH}}_{4}$ analyzer and a closed-path ${\mathrm {CH}}_{4}$ analyzer in a rice paddy field were evaluated with an emphasis on the flux correction methodology. A comparison of the fluxes obtained by the analyzers revealed that both the open-path and closed-path techniques were reliable, provided that appropriate corrections were applied. For the open-path approach, the influence of fluctuations in air density and the line shape variation in laser absorption spectroscopy (hereafter, spectroscopic effect) was significant, and the relative importance of these corrections would increase when observing small ${\mathrm {CH}}_{4}$ fluxes. A new procedure proposed by Li-Cor Inc. enabled us to accurately adjust for these effects. The high-frequency loss of the open-path ${\mathrm {CH}}_{4}$ analyzer was relatively large (11 % of the uncorrected covariance) at an observation height of 2.5 m above the canopy owing to its longer physical path length, and this correction should be carefully applied before correcting for the influence of fluctuations in air density and the spectroscopic effect. Uncorrected ${\mathrm {CH}}_{4}$ fluxes observed with the closed-path analyzer were substantially underestimated (37 %) due to high-frequency loss because an undersized pump was used in the observation. Both the bandpass and transfer function approaches successfully corrected this flux loss. Careful determination of the bandpass frequency range or the transfer function and the cospectral model is required for the accurate calculation of ${\mathrm {CH}}_{4}$ fluxes with the closed-path technique.  相似文献   

Coseismic changes in the chemical composition of volcanic gases from the Owakudani geothermal area on Hakone volcano,Japan     

Takeshi Ohba  Yasushi Daita  Takeshi Sawa  Noriyasu Taira  Yusuke Kakuage 《Bulletin of Volcanology》2011,73(4):457-469

The chemical and isotopic compositions of volcanic gases at a borehole and a natural fumarole in the Owakudani geothermal area, Hakone volcano, Japan, have been repeatedly measured since 2001, when a seismic swarm occurred in the area. The CO₂/H₂O and CO₂/H₂S ratios were high in 2001. It increased in 2006 and again in 2008 when seismic swarms occurred beneath the geothermal area. The observed increases suggest the injection of CO₂- and SO₂-rich magmatic gas into the underlying hydrothermal reservoir, implying that the magmatic gas was episodically supplied to the hydrothermal system in 2006 and 2008. The earthquake swarms probably resulted from the injection of gas through the shallow crust accompanying the break of the sealing zone.  相似文献   

Middle Eocene low-paleolatitude radiolarian evidence for the Cabog Formation,Central East Luzon,Philippine Mobile Belt     

Keisuke Ishida  Shigeyuki Suzuki  Graciano P. Yumul  Carla B. Dimalanta 《Gondwana Research》2011,19(1):61-70

The Cabog Formation, newly established herein and exposed in central East Luzon, Philippine Mobile Belt, is defined in age by the occurrence of radiolarians. The radiolarian assemblage is correlative with the middle Eocene and suggests a low paleolatitude affinity. The correlation, sedimentary environment, and the tectonic significance are discussed. The Cabog Formation is correlative with the distal part of the middle–late Eocene Caraballo Formation, which is exposed in the northeastern side of the Philippine Fault Zone. The sandstone composition and radiolarian age suggest that the Cabog Formation represents the first depositional stage in the early arc setting. The northward migration of the formation is also estimated in relation with the Philippine Sea Plate motion along the Older Philippine Fault from the equatorial area.  相似文献   

Hayabusa‐returned sample curation in the Planetary Material Sample Curation Facility of JAXA     

Toru YADA  Akio FUJIMURA  Masanao ABE  Tomoki NAKAMURA  Takaaki NOGUCHI  Ryuji OKAZAKI  Keisuke NAGAO  Yukihiro ISHIBASHI  Kei SHIRAI  Michael E. ZOLENSKY  Scott SANDFORD  Tatsuaki OKADA  Masayuki UESUGI  Yuzuru KAROUJI  Maho OGAWA  Shogo YAKAME  Munetaka UENO  Toshifumi MUKAI  Makoto YOSHIKAWA  Junichiro KAWAGUCHI 《Meteoritics & planetary science》2014,49(2):135-153

Abstract– The Planetary Material Sample Curation Facility of JAXA (PMSCF/JAXA) was established in Sagamihara, Kanagawa, Japan, to curate planetary material samples returned from space in conditions of minimum terrestrial contaminants. The performances for the curation of Hayabusa‐returned samples had been checked with a series of comprehensive tests and rehearsals. After the Hayabusa spacecraft had accomplished a round‐trip flight to asteroid 25143 Itokawa and returned its reentry capsule to the Earth in June 2010, the reentry capsule was brought back to the PMSCF/JAXA and was put to a series of processes to extract recovered samples from Itokawa. The particles recovered from the sample catcher were analyzed by electron microscope, given their ID, grouped into four categories, and preserved in dimples on quartz slide glasses. Some fraction of them has been distributed for initial analyses at NASA, and will be distributed for international announcement of opportunity (AO), but a certain fraction of them will be preserved in vacuum for future analyses.  相似文献   

Investigation of cutting methods for small samples of Hayabusa and future sample return missions     

Masayuki Uesugi  Ryo Noguchi  Tooru Matsumoto  Junya Matsuno  Takashi Nagano  Akira Tsuchiyama  Shigenori Harada  Kaori Yokoyama  Yoshiaki Yodo  Noboru Takeda  Toru Yada  Shogo Yakame  Yuzuru Karouji  Yukihiro Ishibashi  Masanao Abe  Tatsuaki Okada  Akio Fujimura  Mitsuru Ebihara  Fumio Kitajima  Keisuke Nagao  Tomoki Nakamura  Hiroshi Naraoka  Takaaki Noguchi  Ryuji Okazaki  Hisayoshi Yurimoto 《Meteoritics & planetary science》2014,49(7):1186-1201

We report the investigation of cutting methods for Hayabusa samples. The purpose of our study is to explore the possibility of applying multiple analyses to a single particle effectively. We investigated the cutting performance of a blade dicing saw, laser, focused ion beam (FIB), and physical breaking by microindenter. Cutting performance was examined by estimating the aspect ratio of the cut slit, i.e., depth over width of the slit. We also investigated the possible contamination and sample damage by cutting. The result of the investigation shows that we can cut the samples from <50 μm to 500 μm using those methods with aspect ratios from 10 to 20, although they would introduce some contamination or damage to the samples. Our investigations also provide an important basis for the analysis of samples obtained by future sample return missions.  相似文献   

Fractal structure of spatial distribution of microfracturing in rock   总被引：10，自引：0，他引：10  

Takayuki Hirata  Takashi Satoh  Keisuke Ito 《Geophysical Journal International》1987,90(2):369-374

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