Double-planed deep seismic zone and anomalous structure in the upper mantle beneath northeastern Honshu (Japan)   总被引：1，自引：0，他引：1  

Akira Hasegawa  Norihito Umino  Akio Takagi  Ziro Suzuki 《Tectonophysics》1979,57(1):1-6

Seismicity located by using the most recent data obtained from the high-gain seismograph network of Tohoku University shows that the deep seismic zone beneath northeastern Honshu, Japan, is composed of two thin planes which are parallel to each other and are 30–40 km apart. Focal mechanisms derived from the earthquakes in the upper plane are reverse-faulting, or, some of them, down-dip compression. As a contrast, those in the lower plane are down-dip extension. The location of the upper boundary of the descending lithospheric slab, inferred from the arrival-time difference between ScS and ScSp waves and from the travel-time anomaly of intermediate-depth earthquakes observed at the small-scale seismic array, coincides exactly with the upper plane of the double-planed deep seismic zone. Anelasticity (1/Q) structure of the upper mantle consists of three distinct zones: a high-Q (Qs− 1500) inclined lithospheric slab, an intennediate-Q (Qs−350) land-side mantle between the Pacific coast and the volcanic front, and a low-Q (Qs − 100) land-side mantle between the volcanic front and the coast of the Japan Sea.The evidence obtained here provides valuable information as to the definition of the type of mechanism producing the plate motion beneath island arcs.  相似文献   

Experimental study of the alteration process of labradorite in acid hydrothermal solutions     

Yoshiro Tsuzuki  Kazuhiro Suzuki 《Geochimica et cosmochimica acta》1980,44(5):673-683

Labradorite was altered artificially by HC1 solution ranging from M = 1 to M = 0.003 at 245 and 230°C. The products of alteration were examined by X-ray diffraction, electron microscopy, electron diffraction, infrared spectroscopy and the electron microprobe and the solution was analyzed chemically.Amorphous silica only was formed in solutions with M_HCl = 1 and M_HCl = 0.3. In a solution with M_HCl = 0.2, amorphous silica was initially formed, later dissolved and replaced by kaolinite. A mixture of microcrystalline boehmite and amorphous aluminosilicate was formed, altering to kaolinite in solutions with M_HCl = 0.1 and 0.3. Small amounts of kaolinite were initially formed but the alteration soon stopped in solution with M_HCl = 0.003. Relationships between the alteration processes and pH of the solutions can be roughly explained by using solubility diagrams assuming the congruent dissolution of labradorite and precipitation of the products in partial equilibrium. However, these assumptions are not valid with strongly acid solutions.The rate of dissolution of labradorite is controlled not only by its surface area, but also by the diffusion of matter through the layer of alteration products.  相似文献   

Chromite-bearing spessartites from Kasuga-mura,Japan, and their bearing on possible mantle origin andesite     

Kazuhiro Suzuki  Keiichi Shiraki 《Contributions to Mineralogy and Petrology》1980,71(3):313-322

An unusual association of chromite and hornblende was found in the spessartites of andesite composition, occurring as a dike swarm associated with a Cretaceous granite batholith. The spessartites are largely porphyritic with phenocrysts of either hornblende or augite. One dike, comprising a finegrained spessartite, exhibits distinct chilled selvages of aphanitic facies. The chromites in the fine-grained and augite-spessartites are significantly higher in Cr/ (Cr+Al) than those occurring rarely as inclusions in the phenocrystic hornblendes in the hornblende spessartite, although both are similar in Mg/ (Mg+Fe), Fe₂O₃, and TiO₂. The phenocrystic hornblendes are titaniferous pargasite with high Mg/ (Mg+Fe), and differ in their higher octahedral Al from the groundmass hornblendes including those in the fine-grained spessartite. The crystallization sequence in the phenocrystic hornblende-bearing spessartites is Al-rich chromite, phenocrystic hornblende, and plagioclase without pyroxene, suggesting a high water content in the magma and the start of the crystallization at relatively high pressures. The finegrained spessartite from which the porphyritic spessartites have been derived by fractionation of dominant mafic minerals, has the high Mg-value and Cr content equivalent to those in primitive, undifferentiated basalts, although still andesitic in SiO₂ content. Chemically similar magnesian andesites, although uncommon, found in some orogenic calc-alkalic suites may represent a magma composition in equilibrium with mantle peridotite under the condition of high water pressures.  相似文献   

Anomalous thermal expansion in spinel MgAl2O4     

Isao Suzuki  Mineo Kumazawa 《Physics and Chemistry of Minerals》1980,5(3):279-284

The accurate measurement of thermal expansion in spinel MgAl₂O₄ over a temperature range between 30° C and 900° C has revealed an anomalous behaviour indicating a possible presence of a second order phase transition at 660° C.  相似文献   

Discrimination of spurious self-correlation in nondimensionalized analyses of fluid dynamical data     

Yoshiaki Toba  Naoya Suzuki  Satoru Komori 《Journal of Oceanography》2008,64(3):393-397

Nondimensionalization of variables enables us to treat experiment data much more simply and efficiently by decreasing the number of variables. In some cases, trivial conclusions (which Kenney, 1982, called spurious self-correlation) result from a formal application of dimensional analyses. In contrast, in some cases fully significant conclusions can be derived. We first discuss how to construct nondimensional variables retaining the physical meanings of variables. We then propose simple and efficient methods, especially the use of “spurious triangle (SpT)”, to discriminate between significant conclusions and spurious self-correlations in the analysis of nondimensionalized variables.  相似文献   

Modeling Arctic Ocean heat transport and warming episodes in the 20th century caused by the intruding Atlantic Water     

Jun Takahashi  Tatsuo Suzuki  Igor V Polyakov  Kohei Mizobata  Moto Ikeda  Fancois J.Saucier  Markus Meier 《极地研究(英文版)》2008,19(2):159-167

This study investigates the Arctic Ocean warming episodes in the 20th century using both a high-resolution coupled global climate model and historical observations. The model, with no flux adjustment, reproduces well the Atlantic Water core temperature （AWCT） in the Arctic Ocean and shows that four largest decadalscale warming episodes occurred in the 1930s, 70s, 80s, and 90s, in agreement with the hydrographic observational data. The difference is that there was no pre-warming prior to the 1930s episode, while there were two pre-warming episodes in the 1970s and 80s prior to the 1990s, leading the 1990s into the largest and prolonged warming in the 20th century. Over the last century, the simulated heat transport via Fram Strait and the Barents Sea was estimated to be, on average, 31.32 TW and 14.82 TW, respectively, while the Bering Strait also provides 15.94 TW heat into the west- ern Arctic Ocean. Heat transport into the Arctic Ocean by the Atlantic Water via Fram Strait and the Barents Sea correlates significantly with AWCT （ C = 0.75 ） at 0- lag. The modeled North Atlantic Oscillation （NAO） index has a significant correlation with the heat transport （ C = 0.37 ）. The observed AWCT has a significant correlation with both the modeled AWCT （ C =0.49） and the heat transport （ C =0.41 ）. However, the modeled NAO index does not significantly correlate with either the observed AWCT （ C = 0.03 ） or modeled AWCT （ C = 0.16 ） at a zero-lag, indicating that the Arctic climate system is far more complex than expected.  相似文献   

Numerical calculation of free-surface potential flow around a ship using the modified Rankine source panel method     

Md. Shahjada Tarafder  Kazuo Suzuki 《Ocean Engineering》2008,35(5-6):536-544

A modified Rankine source panel method is presented for solving a linearized free-surface flow problem with respect to the double-body potential. The method of solution is based on the distribution of Rankine sources on the hull as well as its image and on the free surface. An iterative algorithm is used for determining the free surface and wave resistance using upstream finite difference operator. A verification of numerical modeling is made using the Wigley hull and the validity of the computer program is examined by comparing the details of wave profiles and wave making resistance with Series 60 model.  相似文献   

The environments and clustering properties of 2dF Galaxy Redshift Survey selected starburst galaxies     

Matt S. Owers  Chris Blake  Warrick J. Couch  Michael B. Pracy  Kenji Bekki 《Monthly notices of the Royal Astronomical Society》2007,381(2):494-510

We investigate the environments and clustering properties of starburst galaxies selected from the 2dF Galaxy Redshift Survey (2dFGRS) in order to determine which, if any, environmental factors play a role in triggering a starburst. We quantify the local environments, clustering properties and luminosity functions of our starburst galaxies and compare to random control samples. The starburst galaxies are also classified morphologically in terms of their broad Hubble type and evidence of tidal merger/interaction signatures. We find the starburst galaxies to be much less clustered on large (5–15 Mpc) scales compared to the overall 2dFGRS galaxy population. In terms of their environments, we find just over half of the starburst galaxies to reside in low to intermediate luminosity groups, and a further ∼30 per cent residing in the outskirts and infall regions of rich clusters. Their luminosity functions also differ significantly from that of the overall 2dFGRS galaxy population, with the sense of the difference being critically dependent on the way their star formation rates are measured. In terms of pin-pointing what might trigger the starburst, it would appear that factors relating to their local environment are most germane. Specifically, we find clear evidence that the presence of a near neighbour of comparable luminosity/mass within 20 kpc is likely to be important in triggering a starburst. We also find that a significant fraction (20–30 per cent) of the galaxies in our starburst samples have morphologies indicative of either an ongoing or a recent tidal interaction and/or merger. These findings notwithstanding, there remain a significant portion of starburst galaxies where such local environmental influences are not in any obvious way playing a triggering role, leading us to conclude that starbursts can also be internally driven.  相似文献   

Effect of open gap in coastal forest on tsunami run-up—investigations by experiment and numerical simulation     

Nguyen Ba Thuy  Katsutoshi Tanimoto  Norio Tanaka  Kenji Harada  Kosuke Iimura 《Ocean Engineering》2009,36(15-16):1258-1269

The objective of this study is to investigate the effects of an open gap, such as a road, in a coastal forest on tsunami run-up. A numerical model based on two-dimensional nonlinear long-wave equations was developed to account for the effects of drag and turbulence induced shear forces due to the presence of vegetation. Experiments were conducted on a forest simulated with vertical cylinders by changing the gap width. The numerical model was validated in good agreement with the experimental results. The numerical model was then applied to a wide forest of Pandanus odoratissimus, a tree species that is a dominant coastal vegetation on a sand dune in South and Southeast Asia. The effect of vertical stand characteristics of P. odoratissimus with aerial roots was considered on the drag resistance. A straight open gap perpendicular to the shoreline was used to investigate the effect of gap width. As the gap width increases, the flow velocity at the end of the open gap first increases, reaches a maximum, and then decreases, while the run-up height increases monotonously. The maximum velocity in the present condition is 1.7 times the maximum velocity without a coastal forest. The effects of different gap arrangements in the forest on tsunami run-up were also investigated in this paper. The flow velocity at the end of an open gap can be reduced by a staggered arrangement.  相似文献   

Effects of ulvoid (Ulva spp.) accumulation on the structure and function of eelgrass (Zostera marina L.) bed     

Sugimoto K  Hiraoka K  Ohta S  Niimura Y  Terawaki T  Okada M 《Marine pollution bulletin》2007,54(10):1582-1585

The objective of this study is to clarify the effect of ulvoid (Ulva spp.) accumulation on the structure and function of an eelgrass bed by the coast of Iwakuni, Seto Inland Sea, Japan. We monitored eelgrass shoot density and volume of ulvoid accumulation in the study site and evaluated effects of the accumulated ulvoid canopy on the percent survival, seedling density, growth rates, photosynthetic photon flux density (PPFD) and carbon contents of eelgrass. Eelgrass shoot density decreased by the accumulation of ulvoid. Also, seedling density decreased by the increase in the ulvoid volumes. Shoot density, seedling density and leaf elongation were negatively correlated with ulvoid volume. Carbon contents in eelgrass decreased by the accumulation of ulvoid (canopy height: 25cm). These results suggest that accumulation of ulvoid bloom has significant negative impacts on the structure and function of eelgrass bed, i.e. decreases in vegetative shoot density, seedling density, shoot height and growth rate.  相似文献