Aeromagnetic surveys of Kuttyaro and Aso caldera regions,Japan     

H. R. Blank Jr.  S. Aramaki  K. Ono 《Bulletin of Volcanology》1966,29(1):49-50

Detailed total-intensity aeromagnetic surveys of the Kuttyaro and Aso caldera regions, eastern Hokkaido and central Kyushu, were made during early 1964 under the auspices of the U.S.-Japan Co-operative Science Program in conjunction with a project for geophysical studies of calderas in Japan. Each caldera has a maximum diameter of about 22 km; the flights cover a 60 × 60 km rectangular area in each region. The Kuttyaro survey also encompasses the older caldera Akan, south-west of Kuttyaro, and the younger caldera Mashu to the east. All three lie within the Chīshīma (Kurile) volcanic zone. The isomagnetic contour map shows this zone as a belt of short wave-length anomaies which trends east-northeast across the region. Broad wavelength anomalies with trends intersecting the Chīshīma belt at an acute angle probably reflect structural relief on the Neogene volcanic basement concealed beneath Kuttyaro pyroclastic flows. The centre of Kuttyaro caldera coincides with the sharp southern termination of a strong basement high, whereas caldera faults and post-caldera domes have little magnetic expression. Mashu caldera is marked by a minimum in the position of the caldera lake; a symmetrical positive anomaly centering southeast of the caldera suggests either a buried older volcanic edifice or an intrusion. Akan caldera is represented by a magnetic depression encompassing a positive anomaly produced by its central post-caldera cone. The depression extends north of the geologically-deduced boundary of the caldera and may include an earlier collapse structure. Several volcanoes and lava sequences in the region produce negative anomalies due to inverse polarization. The most significant feature of the Aso isomagnetic map is a large, elongate positive anomaly that occupies the southern half of the caldera and extends about one caldera diameter to the south-west along the trend of the Median Tectonic Line of south-west Japan. Whether the anomaly represents the pre-Tertiary basement complex or a younger intrusion perhaps associated with Aso eruptive activity is uncertain. However, the causative body is abruptly truncated within the caldera by a major east-south-east structure passing through the eastern rim and coincident with the approximate locus of resurgent central vent eruptions. The structure may be a fault system that provided egress for the Aso pyroclastic flows. Superimposed on the basement anomaly are the effects of the topography of the caldera, the superficial caldera structure, and the post-caldera cones. An area of intense solfataric activity in the Kuju group of young volcanoes north of Aso has a pronounced negative anomaly. These two surveys illustrate the utility of the magnetic method for investigations of basement structure in caldera regions. They have served as a guide in interpreting reconnaissance aeromagnetic profiles flown concurrently for this project across some 14 other calderas or caldera-like structures in the Japanese islands.  相似文献   

Numerical model studies on the generation and dissipation of the diurnal coastal-trapped waves over the Sakhalin shelf in the Sea of Okhotsk     

Jun Ono  Kay I. Ohshima 《Continental Shelf Research》2010

To clarify the generation and dissipation mechanisms of diurnal coastal-trapped waves (CTWs) over the Sakhalin shelf, a series of numerical experiments were conducted using a three-dimensional tidal model of the Okhotsk Sea with density stratification. The tidal model used has good reproduction owing to the careful fitting to the recent observations. The numerical experiments suggested that diurnal CTWs are primarily (~60%) generated by the conversion of tidal energy at the northern corner of the Sakhalin shelf, and further amplified by vorticity generation due to the water column oscillation from Sakhalin Bay and the influence of Kashevarov Bank. From the observations, it was found that diurnal CTWs are effectively dissipated by the strong spin-down due to bottom friction. The conventional turbulent closure model cannot reproduce the observed damping of diurnal CTWs, which raises a caution in modeling the tidal fields in high-latitude regions where diurnal CTWs exist. To resolve this underestimation of the damping, the vertical eddy viscosity was parameterized using its dependence on the observed major axis length of the diurnal tidal current ellipses, which improves the model reproduction on the damping of diurnal CTWs. The model also suggests that the spin-down effects due to friction associated with the sea-ice cover play an important role in the tidal current reduction in the region where diurnal CTWs exist, as the observations suggested.  相似文献   

Co-ignimbrite ash-fall deposits of the 1991 eruptions of Fugen-dake, Unzen Volcano, Japan     

Kazunori Watanabe  Koji Ono  Keiichi Sakaguchi  Akira Takada  Hideo Hoshizumi 《Journal of Volcanology and Geothermal Research》1999,89(1-4)

Fugen-dake, the main peak of Unzen Volcano, began a new eruption sequence on November 17, 1990. On May 20, 1991, a new lava dome appeared near the eastern edge of the Fugen-dake summit. Small-scale, 10⁴–10⁶ m³ in volume, Merapi-type block and ash flows were frequently generated from the growing lava dome during May–June, 1991. These pyroclastic flows were accompanied by co-ignimbrite ash plumes that deposited ash-fall deposits downwind of the volcano. Three examples of co-ignimbrite ash-fall deposits from Unzen pyroclastic flows are described. The volume of fall deposits was estimated to be about 30% by volume of the collapsed portions of the dome that formed pyroclastic flows. This proportion is smaller than that described for other larger co-ignimbrite ash-fall deposits from other volcanoes. Grain size distributions of the Unzen co-ignimbrite ash-fall deposits are bi-modal or tri-modal. Most ashes are finer than 4 phi and two modes were observed at around 4–7 phi and 9 phi. They are composed mainly of groundmass fragments. Fractions of another mode at around 2 phi are rich in crystals derived from dome lava. Some of the fine ash component fell as accretionary lapilli from the co-ignimbrite ash cloud indicating either moisture or electrostatic aggregation. We believe that the co-ignimbrite ash of Unzen block and ash flows were formed by the mechanical fracturing of the cooling lava blocks as they collapsed and moved down the slope. These ashes were entrained into the convective plumes generated off the tops of the moving flows.  相似文献   

High temperature stability limit of phase egg, AlSiO3(OH)   总被引：1，自引：1，他引：0  

Shigeaki Ono 《Contributions to Mineralogy and Petrology》1999,137(1-2):83-89

The stability relations of phase egg, AlSiO₃(OH), have been investigated at pressures from 7 to 20 GPa, and temperatures from 900 to 1700 °C in a multi-anvil apparatus. At the lower pressures phase egg breaks down according to the univariant reaction, phase egg = stishovite + topaz-OH, which extends from 1100 °C at 11 GPa to 1400 °C at 13 GPa where it terminates at an invariant point involving corundum. At pressures above the invariant point, the stability of phase egg is limited by the breakdown reaction, phase egg = stishovite + corundum + fluid, which extends from the invariant point to 1700 °C at 20 GPa. Stishovite crystallized in the Al₂O₃-SiO₂-H₂O system contains Al₂O₃, and the amount of Al₂O₃ increases with increasing temperature. It is inferred that the Al₂O₃ content is controlled by the charge-balanced substitution of Si⁴⁺ by Al³⁺ and H⁺. Aluminum-bearing stishovite coexisting with an H₂O-rich fluid may contain a certain amount of water. Therefore, phase egg and stishovite in a subducting slab could transport some H₂O into the deep Earth. Received: 14 October 1998 / Accepted: 19 May 1999  相似文献   

Silica minerals in cumulate eucrites: Insights into their thermal histories     

Haruka Ono  Atsushi Takenouchi  Takashi Mikouchi  Akira Yamaguchi 《Meteoritics & planetary science》2019,54(11):2744-2757

Some eucrites contain up to 10 vol% silica minerals; however, silica minerals have not been studied in detail so far. We performed a mineralogical study of silica minerals in three cumulate eucrites (Moore County, Moama, and Yamato [Y] 980433). Monoclinic tridymite was common in all three samples. Moama contained orthorhombic tridymite as lamellae within monoclinic tridymite grains. Y 980433 included quartz around an impact melt vein. The presence of orthorhombic tridymite in Moama indicates that Moama cooled more rapidly than the other two samples at low temperatures (<400 °C). This result is different from the slower cooling rates of Moama (?0.0004 °C yr^?1) than that of Moore County (>0.3 °C yr^?1, after the shock event) at high temperatures (>500 °C) estimated from compositional profiles of pyroxene exsolution lamellae. The difference of the cooling rates may reflect their geological settings. Y 980433 cooled slowly at low temperature, as did Moore County. Quartz in Y 980433 could be a local product transformed from monoclinic tridymite by a shock event. We suggest that silica minerals in meteorites record thermal histories at low temperatures and shock events.  相似文献   

Iron deficiency in micro-sized diatoms in the Oyashio region of the Western subarctic Pacific during spring     

Ai Hattori-Saito  Jun Nishioka  Tsuneo Ono  R. Michael L. McKay  Koji Suzuki 《Journal of Oceanography》2010,66(1):105-115

In order to detect iron (Fe) stress in micro-sized (20–200 μm) diatoms in the Oyashio region, western subarctic Pacific during spring, immunological ferredoxin/flavodoxin assays were applied to samples collected from the surface layer in May 2005. Concomitantly, the community composition of the micro-sized phytoplankton and hydrographic conditions, including dissolved Fe and macronutrient concentrations, were also examined. Chlorophyll (Chl) a concentrations were <2 mg m⁻³ at all sampling stations, except at a station where the Chl a level was 9.0 mg m⁻³ and a micro-sized diatom bloom occurred. A high abundance of ferredoxin in micro-sized diatoms was detected only at a rather near-shore station where dissolved Fe and macronutrient concentrations were higher, indicating that the micro-sized diatoms did not suffer from iron deficiency. On the other hand, flavodoxin in micro-sized diatoms was often observed at the other stations, including the bloom station, where macronutrients were replete but dissolved Fe concentration was low (0.31 nM). A significant amount of chlorophyllide a, a degradation product of Chl a, was also observed at the bloom station, suggesting a decline of the diatom bloom. The micro-sized phytoplankton species at all the stations were mainly composed of the diatoms Thalassiosira, Chaetoceros, and Fragilariopsis spp. Our study indicates that micro-sized diatoms were stressed by Fe bioavailability during the spring season in the Oyashio region  相似文献   

Re-Estimation of Annual Anthropogenic Carbon Input from Oyashio into North Pacific Intermediate Water     

Tsuneo Ono  Katsuyuki Sasaki  Ichiro Yasuda 《Journal of Oceanography》2003,59(6):883-891

The annual transport of anthropogenic carbon (C_anth) to the North Pacific Intermediate Water (NPIW) from the Western Subarctic Gyre (WSG) has been re-estimated by using newly estimated Oyashio transport and C_anth concentration, the latter calculated by the recently-established “ΔC*” method with some modifications. Estimated annual C_anth transport through the nearshore Oyashio west of 146°E was 0.020 ± 0.010 GtC y⁻¹, closely approximating the previous estimation based on a 1-D model calibrated with the CFC vertical distribution. The present study, however, found that an additional 0.025 ± 0.010 GtC y⁻¹ of C_anth was transported into NPIW in the region east of 146°E. Total C_anth transport, 0.045 GtC y⁻¹, contributes about 35% of annual C_anth accumulation of the whole temperate North Pacific. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Optical depth,size distribution and flux of dust from Owens Lake,California     

Tezz C. Niemeyer  Dale A. Gillette  John J. DeLuisi  Young J. Kim  William F. Niemeyer  Trevor Ley  Thomas E. Gill  Duane Ono 《地球表面变化过程与地形》1999,24(5):463-479

A joint United States/Russian/French collaborative experiment was undertaken in March 1993 and March 1996. Projects LODE I and II (Lake Owens Dust Experiments) took place on the anthropogenically desertified playa (dry lakebed) and surrounding regions of Owens Lake, in east-central California. One of the five parts of Project LODE was to determine relationships between optical depth and flux of dust emitted from the dry lake. Project LODE II included subsequent dust plume measurements and size distributions obtained through April 1996, to further refine the flux measurements for distinct mineral aerosol source regions at Owens Lake. Size distributions of dust aerosol were determined and aerosol optical depths were calculated from sunphotometer solar extinction measurements taken downwind in plumes coming from the emissive areas of Owens Lake. This source was visually observed for 10 measured dust storms. The plume mass was calculated to be 1·5 × 10⁹ g using ground-based measurements and ≥1·6 × 10⁹ g from satellite data. Project LODE II results were found to be consistent with LODE I results for the south end of the playa, but flux values were found to be reduced for the northeastern portion of the playa by comparison. Vertical flux values estimated by sunphotometry were found to be consistent with values estimated via a micrometeorological method. Copyright © 1999 John Wiley & Sons, Ltd.  相似文献   

Response uncertainty and time-variant reliability analysis for hysteretic MDF structures     

Y. G. Zhao  T. Ono  H. Idota 《地震工程与结构动力学》1999,28(10):1187-1213

Response uncertainty evaluation and dynamic reliability analysis corresponding to classical stochastic dynamic analysis are usually restricted to the uncertainties of the excitation. The inclusion of the parameter uncertainties contained in structural properties and excitation characteristics has become an increasingly important problem in many areas of dynamics. In the present paper, a point estimate procedure is proposed for the evaluation of stochastic response uncertainty, and a response surface approach procedure in standard normal space is proposed for analysis of time-variant reliability analysis for hysteretic MDF structures having parameter uncertainties. Using the proposed procedures, the response uncertainties and time-variant reliability can be easily obtained by several repetitions of stochastic response analysis under given parameters without conducting sensitivity analysis, which is considered to be one of the primary difficulties associated with conventional methods. In the time-variant reliability analysis, the failure probability can be readily obtained by improving the accuracy of the first-order reliability method using the empirical second-order reliability index. The random variables are divided into two groups, those with CDF and those without CDF. The latter are included via the high-order moment standardization technique. A numerical example of a 15F hysteretic MDF structure that takes into account uncertainties of four structural parameters and three excitation characteristics is performed, based on which the proposed procedures are investigated and the effects of parameter uncertainties are discussed. Copyright © 1999 John Wiley & Sons, Ltd.  相似文献   

Volume transport in the Soya Strait during 2006–2008     

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