Three-dimensional P-wave velocity structure in the upper crust beneath Kuju Volcano, central Kyushu, Japan     

Yasuaki Sudo  Yoshihiro Matsumoto 《Bulletin of Volcanology》1998,60(3):147-159

 Kuju Volcano lies near Aso Caldera at the center of Kyushu Island, western Japan. After a few hundred years of dormancy, a phreatic explosion accompanied by a small ash eruption occurred on 11 October 1995. This study was undertaken to determine the subsurface seismic velocity structure associated with the active magmatic regime in the Kuju volcanic region. The three-dimensional, upper crustal, P-wave velocity structure beneath Kuju Volcano was determined using methods for the simultaneous inversion of P-wave arrival times from local earthquakes in and around the Kuju volcanic region for velocities and hypocentral parameters. Results reveal two shallower low-velocity anomalies located in the northern and southern parts of Kuju Volcano, consistent with the presence of significant negative Bouguer gravity anomalies. In addition, a high-velocity anomaly is located approximately 5 km northwest of Mt. Kuju, one of the domes in Kuju Volcano. Beneath this high-velocity anomaly, a low-velocity anomaly is present. This velocity structure suggests a magmatic regime that has a lid consisting of cooled solid material overlying a chamber of partially molten material. Received: 23 September 1997 / Accepted: 20 June 1998  相似文献   

Partitioning of heavy metals into mineral and organic fractions in a sediment core sample from Osaka Bay     

Yasushi Kitano  Masahiro Sakata  Eiji Matsumoto 《Journal of Oceanography》1981,37(5):259-266

Partitioning of copper, zinc, iron and manganese into oxide, sulfide, organic and silicate fractions has been determined with a selective chemical leaching technique on sediment samples from a core collected in Osaka Bay. The samples have been dated by the²¹⁰Pb method. Most of the copper and zinc in the polluted surface sediment layer are contained in both oxide and sulfide fractions. This suggests that the transformation of oxides and hydroxides to sulfides under anoxic conditions within the sediment is significant for the fixation of copper and zinc discharged through human activities into the sediment. Manganese is apparently enriched in oxide and hydroxide fractions of the surface layer due to the post-depositional migration of manganese within the sediment. The copper, zinc and manganese contents of the 30 % H₂O₂ soluble fraction (mostly organic fraction) decrease with depth in the sediment core, and correlate significantly with the organic carbon content. The heavy metal (Cu, Zn, Fe and Mn) contents of the silicate fraction, without exchangeable sites, are almost constant with depth.  相似文献   

Experimental studies on the possible influences of composition changes of pore water on the stability conditions of methane hydrate in marine sediments   总被引：4，自引：1，他引：4  

Hailong Lu  Ryo Matsumoto 《Marine Chemistry》2005,93(2-4):149-157

Experiments with a set of electrolyte solutions have been carried out to investigate the effects of pore water composition changes on the stability conditions of methane hydrate in marine sediments. The results reveal that (1) SO₄²⁻ and Cl⁻ concentration changes can affect hydrate stability slightly, (2) the changes in both the type and the concentration of cations, which occur in normal diagenetic processes, do not exert a significant influence on the methane hydrate stability conditions, and (3) the shift of hydrate stability in pore water can be expressed as a function of the Cl⁻ concentration only. Based on the results above, an empirical equation ΔT (K)=0.00206 Cl⁻ (mmol/dm³) has been obtained for estimating the shift in the equilibrium temperature of methane hydrate in pore water at a given pressure.  相似文献   

日本海东缘海洋天然气水合物矿藏之上的甲烷羽状流--地下甲烷运移到浅水的可能机制     

Ryo Matsumoto  龚建明 《海洋地质前沿》2006,22(5):33-33

在日本海会聚边缘的东侧,第三纪沉积物厚度大、有机质丰富,是日本最好的油气区。2003—2004年,在对该区南部的Naoetsu盆地中的UT-04海岭进行调查时,日本METI和JOG-MEC意外地发现了与气体活动有关的较大的麻坑、浅表层含气沉积物以及充气泥丘。高精度地震调查证实海底之下约170  相似文献   

Trends and factors governing polycyclic aromatic hydrocarbon levels in Tokyo Bay sediments     

Keiichi Ohta  Nobuhiko Handa  Eiji Matsumoto 《Geochimica et cosmochimica acta》1983,47(9):1651-1654

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Biological organic carbon export estimated from the annual carbon budget observed in the surface waters of the western subarctic and subtropical North Pacific Ocean from 2004 to 2013     

Masahide Wakita  Makio C. Honda  Kazuhiko Matsumoto  Tetsuichi Fujiki  Hajime Kawakami  Sayaka Yasunaka  Yoshikazu Sasai  Chiho Sukigara  Mario Uchimiya  Minoru Kitamura  Toru Kobari  Yoshihisa Mino  Akira Nagano  Shuichi Watanabe  Toshiro Saino 《Journal of Oceanography》2016,72(5):665-685

The annual flux of biologically produced organic carbon from surface waters is equivalent to annual net community production (NCP) at a steady state and equals the export of particulate and dissolved organic carbon (POC and DOC, respectively) to the ocean interior. NCP was estimated from carbon budgets of salinity-normalized dissolved inorganic carbon (nDIC) inventories at two time-series stations in the western subarctic (K2) and subtropical (S1) North Pacific Ocean. By using quasi-monthly biogeochemical observations from 2004 to 2013, monthly mean nDIC inventories were integrated from the surface to the annual maximum mixed layer depth and corrected for changes due to net air–sea CO₂ exchange, net CaCO₃ production, vertical diffusion from the upper thermocline, and horizontal advection. The annual organic carbon flux at K2 (1.49 ± 0.42 mol m^?2 year^?1) was lower than S1 (2.81 ± 0.53 mol m^?2 year^?1) (p < 0.001 based on t test). These fluxes consist of three components: vertically exported POC fluxes (K2: 1.43 mol m^?2 year^?1; S1: 2.49 mol m^?2 year^?1), vertical diffusive DOC fluxes (K2: 0.03 mol m^?2 year^?1; S1: 0.25 mol m^?2 year^?1), and suspended POC fluxes (K2: 0.03 mol m^?2 year^?1; S1: 0.07 mol m^?2 year^?1). The estimated POC export flux at K2 was comparable to the sum of the POC flux observed with drifting sediment traps and active carbon flux exported by migrating zooplankton. The export fluxes at both stations were higher than those reported at other time-series sites (ALOHA, the Bermuda Atlantic Time-series Study, and Ocean Station Papa).  相似文献   

Comparison of sinking particles in the upper 200 m between subarctic station K2 and subtropical station S1 based on drifting sediment trap experiments     

Makio C. Honda  Hajime Kawakami  Kazuhiko Matsumoto  Masahide Wakita  Tetsuichi Fujiki  Yoshihisa Mino  Chiho Sukigara  Toru Kobari  Mario Uchimiya  Ryo Kaneko  Toshiro Saino 《Journal of Oceanography》2016,72(3):373-386

Drifting sediment trap experiments were conducted during various seasons to elucidate the characteristics of particles sinking through the upper 200 m of the water column in the western Pacific at subarctic station K2 and subtropical station S1. The sinking particle flux increased when primary productivity was high at each station, during June–July at K2 and during February at S1. Biogenic opal (Opal) and CaCO₃ were the major components of the fluxes at K2 and S1, respectively. Contrary to the expectation of a high flux at the eutrophic station K2 and low flux at the oligotrophic station S1, the annual average organic carbon fluxes at 100 m were comparable at both stations: 62.7 mg C m^?2 day^?1 at K2 and 56.1 mg C m^?2 day^?1 at S1. The similarity of the fluxes was perhaps a reflection of the unexpectedly high primary production at S1. At K2, the organic carbon export ratio (organic carbon flux/primary productivity) was significantly and negatively correlated with primary production and tended to decrease with depth. The magnitude of the rate of attenuation of the organic carbon flux with depth was larger at S1 than at K2. This rate of attenuation tended to decrease and increase with primary production at K2 and S1, respectively. The explanation for these patterns may be that the flux of labile organic carbon at relatively shallow depths decreased with increasing primary production at K2, and zooplankton grazing pressure increased with increasing primary productivity at S1.  相似文献   

Seasonal variability of phytoplankton community structure in the subtropical western North Pacific     

Tetsuichi Fujiki  Kosei Sasaoka  Kazuhiko Matsumoto  Masahide Wakita  Yoshihisa Mino 《Journal of Oceanography》2016,72(3):343-358

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Franciscan eclogite revisited: Reevaluation of the P–T evolution of tectonic blocks from Tiburon Peninsula, California, U.S.A.     

T. Tsujimori  K. Matsumoto  J. Wakabayashi  J. G. Liou 《Mineralogy and Petrology》2006,88(1-2):243-267

Summary High-grade blocks in the Franciscan complex at Tiburon, California, record relatively low temperature eclogite-facies metamorphism and blueschist-facies overprinting. The eclogite-facies mineral assemblage contains prograde-zoned garnet + omphacite + epidote ± hornblende (katophoritic and barroisitic Ca–Na amphibole) ± glaucophane + phengite (∼3.5 Si p.f.u.) ± paragonite + rutile + quartz. The blueschist-facies mineral assemblage contains chlorite + titanite + glaucophane + epidote ± albite ± phengite (∼3.3 Si p.f.u.). Albite is not stable in the eclogite stage. New calculations based on garnet-omphacite-phengite thermobarometry and THERMOCALC average-P–T calculations yield peak eclogite-facies P–T conditions of P = 2.2–2.5 GPa and T = 550–620 °C; porphyroclastic omphacite with inclusions of garnet and paragonite yields an average-P–T of 1.8 ± 0.2 GPa at 490 ± 70 °C for the pre-peak stage. The inferred counterclockwise hairpin P–T trajectory suggests prograde eclogitization of a relatively “cold” subducting slab, and subsequent exhumation and blueschist-facies recrystallization by a decreasing geotherm. Although an epidote-garnet amphibolitic assemblage is ubiquitous in some blocks, P–T pseudosection analyses imply that the epidote-garnet amphibolitic assemblage is stable during prograde eclogite-facies metamorphism. Available geochronologic data combined with our new insight for the maximum pressure suggest an average exhumation rate of ∼5 km/Ma, as rapid as those of some ultrahigh pressure metamorphic terranes.  相似文献   

Two recent flowslides in Yamashina area, Kanazawa City, Japan     

Fa-Wu Wang  Tatsunori Matsumoto  Yasuhiro Tanaka 《Landslides》2006,3(1):84-84

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