Yamato 792947, 793408 and 82038: The most primitive H chondrites,with abundant refractory inclusions     

M. Kimura  H. Hiyagon  H. Palme  B. Spettel  D. Wolf  R. N. Clayton  T. K. Mayeda  T. Sato  A. Suzuki  H. Kojima 《Meteoritics & planetary science》2002,37(10):1417-1434

Abstract— In this paper we report petrological and chemical data of the unusual chondritic meteorites Yamato (Y)‐792947, Y‐93408 and Y‐82038. The three meteorites are very similar in texture and chemical composition, suggesting that they are pieces of a single fall. The whole‐rock oxygen isotopes and the chemical compositions are indicative of H chondrites. In addition, the mineralogy, and the abundances of chondrule types, opaque minerals and matrices suggest that these meteorites are H3 chondrites. They were hardly affected by thermal and shock metamorphism. The degree of weathering is very low. We conclude that these are the most primitive H chondrites, H3.2–3.4 (S1), known to date. On the other hand, these chondrites contain extraordinarily high amounts of refractory inclusions, intermediate between those of ordinary and carbonaceous chondrites. The distribution of the inclusions may have been highly heterogeneous in the primitive solar nebula. The mineralogy, chemistry and oxygen isotopic compositions of inclusions studied here are similar to those in CO and E chondrites.  相似文献   

Multi-approach characterization of shallow-water carbonates off Minamitorishima and their depositional settings/history     

Md. Aftabuzzaman  Kazuki Yomogida  Shota Suzuki  Hideko Takayanagi  Akimasa Ishigaki  Shiki Machida  Yoshihiro Asahara  Koshi Yamamoto  Naoto Hirano  Shin-Ichi Sano  Shun Chiyonobu  Davide Bassi  Yasufumi Iryu 《Island Arc》2021,30(1):e12400

Sedimentological, geochemical, and chronological analyses were carried out on 18 carbonate rock samples collected at depths of 938, 1085, and 3354 m on the western slope of Minamitorishima (Marcus Island), which is located near the western margin of the Pacific Plate. Four groups of carbonate rocks were distinguished: a mollusk-rich limestone, a coral-rich dolomite, a foraminiferal-nannofossil packstone, and a phosphatized mudstone/wackestone. The mollusk-rich limestone is characterized by the dominance of bivalves (including rudists) and gastropod shells. Strontium isotope ratios (⁸⁷Sr/⁸⁶Sr) and Mesorbitolina ex gr. texana (a large benthic foraminifer) indicate that the shallow-water carbonates were deposited during the late Aptian–early Albian (ca. 123–111 Ma). The coral-rich dolomite is characterized by abundant scleractinian corals and nongeniculate coralline algae associated with encrusting acervulinid foraminifers. The biotic composition is similar to that of the Oligocene–Pleistocene carbonates reported from other seamounts in the northwestern Pacific. Geochemical data show that the coral-rich carbonates were dolomitized at 9.5–6.8 Ma (Tortonian–Messinian) and that normal seawater was the most likely parent fluid. The foraminiferal-nannofossil packstone is a semi-consolidated foraminiferal-nannofossil ooze and was deposited during the Pleistocene (0.99–0.45 Ma). The phosphatized mudstone/wackestone is marked by the absence of macrofossils and the presence of traces of planktic foraminifers. Although its depositional age is not constrained, the Sr isotope ratios indicate that the phosphatization occurred at 33.2–28.9 Ma. After the deposition of the Cretaceous shallow-water carbonates, including the mollusk-rich limestone, Minamitorishima was drowned and its top was covered with a pelagic cap, represented by the mudstone/wackestone. The late Eocene–early Oligocene volcanism (40.2–33.2 Ma) caused episodic uplift and returned the top of Minamitorishima to a shallow-water environment. After the early Oligocene phosphatization of the pelagic cap, coral reefs flourished on the top of this island. The reef limestone was dolomitized during the Tortonian–Messinian.  相似文献   

Detailed paleoseismic history of the Hinagu fault zone revealed by the high-density radiocarbon dating and trenching survey across a surface rupture of the 2016 Kumamoto earthquake,Kyushu, Japan     

Yoshiki Shirahama  Yukari Miyashita  Masao Kametaka  Yuji Suzuki  Yosuke Miyairi  Yusuke Yokoyama 《Island Arc》2021,30(1):e12376

The NE-trending Hinagu fault zone, length 81 km, is one of the major active faults in Kyushu, Japan. From north to south, it is divided into three segments based on geomorphic features and paleoseismic behavior: the Takano-Shirahata, Hinagu, and Yatsushiro Sea segments. The 2016 Kumamoto earthquake produced a 6-km-long surface rupture with a dextral strike-slip displacement on the northern part of the Takano-Shirahata segment. Surface rupture, a faint east-side-up flexure with a vertical offset of less than 8 cm, was observed near the middle of the Takano-Shirahata segment. To examine past surface-rupturing earthquakes on the Takano-Shirahata segment, including rupture frequency and timing, we conducted a paleoseismic study with boring and trenching at Yamaide. A trench across the surface rupture exposed multiple fault strands associated with multiple surface-rupturing events that deformed several strata of fine-grained sediments. By structural and stratigraphic interpretation, high-density radiocarbon dating and tephra analysis, and Bayesian modeling, we constrained the timing of seven events, Events 1–7, to 0.84–1.25, 1.31–7.06, 9.99–11.0, 10.8–12.1, 12.0–13.0, 14.2–15.1, and before 14.8 kcal BP. Slip during Events 1–6 was obviously larger than the 2016 slip. The estimated average recurrence interval was about 2596–2860 years, but the interval between Events 2 and 3 was much longer than other intervals. Moreover, the vertical throw associated with Event 2 was larger than that of other events. This implies that the Takano-Shirahata segment has a period with rare larger earthquakes and a period with frequent smaller earthquakes. Some events might have produced ruptures on both the Takano-Shirahata and the northern part of the Hinagu segments simultaneously or in a short time. The variety of recurrence intervals suggests that the seismic activity has been affected by one or both activities of the Futagawa fault zone and the Hinagu segment.  相似文献   

Density measurements of liquid Fe–Si alloys at high pressure using the sink–float method     

Ryuji Tateyama  Eiji Ohtani  Hidenori Terasaki  Keisuke Nishida  Yuki Shibazaki  Akio Suzuki  Takumi Kikegawa 《Physics and Chemistry of Minerals》2011,38(10):801-807

The compositional dependence on the density of liquid Fe alloys under high pressure is important for estimating the amount of light elements in the Earth’s outer core. Here, we report on the density of liquid Fe–Si at 4 GPa and 1,923 K measured using the sink–float method and our investigation on the effect of the Si content on the density of the liquid. Our experiments show that the density of liquid Fe–Si decreases from 7.43 to 2.71 g/cm³ non-linearly with increasing Si content (0–100 at%). The molar volume of liquid Fe–Si calculated from the measured density gradually decreases in the compositional range 0–50 at% Si, and increases in the range 50–100 at% Si. It should be noted that the estimated molar volume of the alloys shows a negative volume of mixing between Fe and Si. This behaviour is similar to Fe–S liquid (Nishida et al. in Phys Chem Miner 35:417–423, 2008). However, the excess molar volume of mixing for the liquid Fe–Si is smaller than that of liquid Fe–S. The light element contents in the outer core estimated previously may be an underestimation if we take into account the possible negative value of the excess mixing volume of iron–light element alloys in the outer core.  相似文献   

Was the 2011 Tohoku-Oki earthquake preceded by aseismic preslip? Examination of seafloor vertical deformation data near the epicenter     

R. Hino  D. Inazu  Y. Ohta  Y. Ito  S. Suzuki  T. Iinuma  Y. Osada  M. Kido  H. Fujimoto  Y. Kaneda 《Marine Geophysical Researches》2014,35(3):181-190

Ocean-bottom pressure records obtained near the epicenter of the 2011 Tohoku-Oki earthquake were examined to test whether the earthquake was preceded by substantial precursory crustal deformation. The seafloor data enabled us to search for small-scale preslip near the epicenter that would be difficult to identify from terrestrial geodetic data. After treating the data to reduce nontectonic fluctuations, we obtained a time series of seafloor vertical deformation in the epicentral region with a noise level of 2–4 cm. No significant crustal deformation related to preslip was detected in the period of roughly a day before the mainshock, whereas postseismic deformation associated with the largest foreshock 2 days before the mainshock was apparent. From our quantitative estimate of the sensitivity of the seafloor network in detecting slip on the plate interface, we conclude that the Tohoku-Oki earthquake was not preceded by preslip with moment release greater than moment magnitude (Mw) 6.2 in the vicinity of the hypocenter or greater than Mw 6.0 along the subduction interface near the trench.  相似文献   

Magma discharge variations during the 2011 eruptions of Shinmoe-dake volcano, Japan, revealed by geodetic and satellite observations     

Tomofumi Kozono  Hideki Ueda  Taku Ozawa  Takehiro Koyaguchi  Eisuke Fujita  Akihiko Tomiya  Yujiro J Suzuki 《Bulletin of Volcanology》2013,75(3):1-13

We present precise geodetic and satellite observation-based estimations of the erupted volume and discharge rate of magma during the 2011 eruptions of Kirishima-Shinmoe-dake volcano, Japan. During these events, the type and intensity of eruption drastically changed within a week, with three major sub-Plinian eruptions on January 26 and 27, and a continuous lava extrusion from January 29 to 31. In response to each eruptive event, borehole-type tiltmeters detected deflation of a magma chamber caused by migration of magma to the surface. These measurements enabled us to estimate the geodetic volume change in the magma chamber caused by each eruptive event. Erupted volumes and discharge rates were constrained during lava extrusion using synthetic aperture radar satellite imaging of lava accumulation inside the summit crater. Combining the geodetic volume change and the volume of lava extrusion enabled the determination of the erupted volume and discharge rate during each sub-Plinian event. These precise estimates provide important information about magma storage conditions in magma chambers and eruption column dynamics, and indicate that the Shinmoe-dake eruptions occurred in a critical state between explosive and effusive eruption.  相似文献   

Solar Rotation Rate during Solar Activity Cycle 23     

Miyoshi Suzuki 《Solar physics》2012,278(2):257-267

We studied the solar rotation rate and its temporal change, using the sunspot data obtained during activity cycle 23 (1996 – 2006). The equatorial rotation rate is nearly the same as in the former cycle 22, while the latitudinal gradient of differential rotation considerably increased. Comparison of our results with others indicates the existence of a long-term periodicity of about eight cycles in differential rotation. In addition, no significant asymmetry in differential rotation between the northern and southern hemispheres during cycle 23 was found. The equatorial rotation rate and the latitudinal gradient of the differential rotation in the period of cycle 23 are approximately constant, except for the initial and final phases in the cycle.  相似文献   

Microbial community respiration and structure of dead zone sediments of Omura Bay, Japan   总被引：1，自引：0，他引：1  

Minoru Wada  Shotaro Suzuki  Tadashi Nara  Yu Umezawa  Motohiro Shimanaga  Kazumi Matsuoka  Hideaki Nakata 《Journal of Oceanography》2012,68(6):857-867

Monitoring sediment microbial community metabolism and structure is instrumental to understanding biogeochemical processes in and ecological impacts on bottom environments. The aim of this study was to determine potential community respiration and to reveal community dynamics of the microorganisms in the dead zone sediments of Omura Bay, Japan. The bay is highly enclosed and develops severe hypoxia in the central regions every summer. We collected sediment core samples from the center of the bay during hypoxia, estimated sediment oxygen consumption by using an adapted in vivo electron transport system activity (in vivo ETSA) assay, enumerated abundance of bacteria, and analyzed bacterial community structure by automated ribosomal intergenic spacer analysis. Higher ETSA and bacterial diversity were found in upper sediments (within 3?cm depth) from the center than the fringe of the bay. Sediment bacterial community structure of the bay center was distinct from that of the fringe. From these results, upper sediment in the dead zone of Omura Bay was characterized by (1) greater community respiration and (2) greater diversity of bacterial components compared with the non-hypoxic sediment of the bay fringe. These characteristics have important implications for understanding the interaction between microbial communities and the development of hypoxia in Omura Bay.  相似文献   

Wave dissipation by vegetation with layer schematization in SWAN   总被引：1，自引：0，他引：1  

Tomohiro Suzuki  Marcel ZijlemaBastiaan Burger  Martijn C. MeijerSiddharth Narayan 《Coastal Engineering》2012,59(1):64-71

The energy of waves propagating through vegetation is dissipated due to the work done by the waves on the vegetation. Dalrymple et al. (1984) estimated wave dissipation by integrating the force on a cylinder over its vertical extent. This was extended by Mendez and Losada (2004) to include varying depths and the effects of wave damping due to vegetation and wave breaking for narrow-banded random waves. This paper describes the wave dissipation over a vegetation field by the implementation of the Mendez and Losada formulation in a full spectrum model SWAN, with an extension to include a vertical layer schematization for the vegetation. The present model is validated with the original equation and results from Mendez and Losada (2004). The sensitivity of the model to the shape of the frequency spectrum, directional spreading and layer schematization are investigated. The model is then applied to field measurements by using a vegetation factor. This model has the ability to calculate two-dimensional wave dissipation over a vegetation field including some important aspects such as breaking and diffraction as used in SWAN model.  相似文献   

Prolonged impact of earthquake-induced landslides on sediment yield in a mountain watershed: The Tanzawa region, Japan   总被引：5，自引：0，他引：5  

Takashi Koi  Norifumi Hotta  Ituro Ishigaki  Norimasa Matuzaki  Yoshimi Uchiyama  Masakazu Suzuki 《Geomorphology》2008,101(4):692-702

To determine for how long a landslide affects sediment discharge, the sediment yields of 15 check-dam basins were compared with the time series of landslide distributions in a mountain basin in the Tanzawa region, central Japan. The distribution of sediment yield was quantitatively estimated from deposition in the sediment pools of check dams. The relationship between the landslide history and sediment discharge in the Nakagawa River basin was examined for an approximately 80-year period. Two major landslide events occurred during this period: the 1923 Kanto Earthquake and the 1972 disaster caused by heavy rainfall. The resulting trend in sediment discharge of the whole basin, estimated using reservoir sedimentation in the Miho Dam at its base, was nearly constant, with high sediment discharge (2897 m³ km^− 2 yr^− 1) in the intervening quarter-century, despite the recovery of vegetation on landslide areas in this period. Comparisons of the landslide distributions resulting from the two disasters, the sediment yields of check-dam basins, and the sediment discharge of the whole basin indicate that recent sediment discharge contains landslide debris that was originated by the Kanto Earthquake that occurred over 80 years ago. Thus, to understand high sediment discharge, it is essential to investigate not only the current basin condition and recent events, but also the landslide history of the basin for at least the previous 100 years.  相似文献