Late Cenozoic volcanic activity in the Chugoku area, southwest Japan arc during back-arc basin opening and reinitiation of subduction   总被引：3，自引：0，他引：3  

Jun-Ichi Kimura  Tomoyuki Kunikiyo  Isaku Osaka  Takashi Nagao  Seiki Yamauchi  Susumu Kakubuchi  Shomei Okada  Norie Fujibayashi  Ryuhei Okada  Hisashi Murakami  Takashi Kusano  Koji Umeda  Shintaro Hayashi  Tsuneari Ishimaru  Atusi Ninomiya  Atsushi Tanase 《Island Arc》2003,12(1):22-45

Abstract Temporal–spatial variations in Late Cenozoic volcanic activity in the Chugoku area, southwest Japan, have been examined based on 108 newly obtained K–Ar ages. Lava samples were collected from eight Quaternary volcanic provinces (Daisen, Hiruzen, Yokota, Daikonjima, Sambe, Ooe–Takayama, Abu and Oki) and a Tertiary volcanic cluster (Kibi Province) to cover almost all geological units in the province. Including published age data, a total of 442 Cenozoic radiometric ages are now available. Across‐arc volcanic activity in an area approximately 500 km long and 150 km wide can be examined over 26 million years. The period corresponds to syn‐ and post‐back‐arc basin opening stages of the island arc. Volcanic activity began in the central part of the rear‐arc ca 26 Ma. This was followed by arc‐wide expansion at 20 Ma by eruption at two rear‐arc centers located at the eastern and western ends. Expansion to the fore‐arc occurred between 20 and 12 Ma. This Tertiary volcanic arc was maintained until 4 Ma with predominant alkali basalt centers. The foremost‐arc zone activity ceased at 4 Ma, followed by quiescence over the whole arc between 4 and 3 Ma. Volcanic activity resumed at 3 Ma, covering the entire rear‐arc area, and continued until the present to form a Quaternary volcanic arc. Adakitic dacite first occurred at 1.7 Ma in the middle of the arc, and spread out in the center part of the Quaternary volcanic arc. Alkali basalt activities ceased in the area where adakite volcanism occurred. Fore‐arc expansion of the volcanic arc could be related to the upwelling and expansion of the asthenosphere, which caused opening of the Japan Sea. Narrowing of the volcanic zone could have been caused by progressive Philippine Sea Plate subduction. Deeper penetration could have caused melting of the slab and resulted in adakites. Volcanic history in the Late Cenozoic was probably controlled by the history of evolution of the upper mantle structure, coinciding with back‐arc basin opening and subsequent reinitiation of subduction.  相似文献   

Filamentation Instability of Nonlinear Alfvén Waves and Plasma Heating associated with Recombination Effect     

M. Suzuki  J. I. Sakai 《Solar physics》1998,178(1):43-53

We investigate plasma heating associated with the effect of recombination and the filamentation instability of Alfvén waves propagating along homogeneous magnetic field in low-beta plasmas, by using an MHD simulation code. The linear instability of Alfvén waves leading to the filamentation is investigated by imposing small density perturbations across a magnetic field. We show results of the nonlinear stage of the above filamentation instability and the plasma heating through a two-dimensional simulation. It is shown that the plasma heating is caused by localized heating and whole heating, which are associated with the filamentation instability and the effect of recombination, respectively. We discuss the implication of these results for plasma heating processes observed in the chromosphere of the Sun.  相似文献   

The Rotation of Sunspots During Activity Cycle 22     

Suzuki  Miyosi 《Solar physics》1998,178(2):259-265

The solar rotation rate derived from the measurements of daily sunspot positions during activity cycle 22 (1988–1996) are presented. The averaged differential rotation is nearly symmetric with respect to the equator. The comparisons of our measurement with those for previous cycles show that the equatorial rotation rate gradually increases from cycle 18 to 22.  相似文献   

Lateral structural variation across a collision zone in central Hokkaido, Japan, as revealed by wide-angle seismic experiments     

Takaya Iwasaki  Oguz Ozel  Takeo Moriya  Shin'ichi Sakai  Sadaomi Suzuki  Gen Aoki  Takuya Maeda†  & Takashi Iidaka 《Geophysical Journal International》1998,132(2):435-457

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Late Olenekian Radiolarians from Bedded Chert of Ashio Terrane, Northeast Japan,and Faunal Turnovers in Western Panthalassa during Early Triassic     

NoritoshiSuzuki  NatsumiAkiba 《中国地质大学学报(英文版)》2002,13(2):124-140,T001

Late Olenekian assemblages in the western Panthalassa have been recovered from bedded radiolarian chert sequences of an accretionary complex, the Ashio belt. These faunas are documented and considered in terms of radiolarian diversity and faunal turnover during the latest Permian to Middle Triassic time. The fauna includes 30 radiolarians belonging to Spumellaria or Entactinaria, with two relicts from the Late Permian. This late Olenekian fauna is markedly different from Permian and Asisian faunas, respectively, and is herein named the Minowa fauna. Study of the literaure indicates that radiolarian provinces were significantly disconnected between the western Panthalassa and eastern Tethys during late Olenekian time. Furthermore, 121 of 143 species disappeared during late Olenekian time, and in turn 118 new species appeared in the western Panthalassa around the Olenekian-Anisian boundary. It is concluded that faunal turnover occurred at least three times between the latest Permian and Middle Triassic.The first turnover is the Poalaozoie-type radiolarian extinction at the Permain-Triassic boundary,the second is the diversification of spheroidal Spumellaria and Entactinaria between early and late Olenekian time, and the third is a faunal turnover from the Minowa fauna to the true Mesozoic-type radiolarian famas that are characterized by mulit0segmented Nassellaria.  相似文献   

Seismic activity in the northeastern Japan arc     

Akio Takagi  Akira Hasegawa  Norihito Umino  Ziro Suzuki 《Physics of the Earth and Planetary Interiors》1979,18(4):351-354

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Thermal expansion of single-crystal tephroite     

Shinichi Okajima  Isao Suzuki  Kiyoshi Seya  Yoshio Sumino 《Physics and Chemistry of Minerals》1978,3(2):111-115

The thermal expansion of tephroite (Mn₂SiO₄) at temperatures between 25 and 850°C has been determined by a dilatometric technique. The analysis of data in terms of Grüneisen's theory yields the Grüneisen's parameter γ=1.04, and the pressure derivative of rigidity (?G/?P)=0.7.  相似文献   

Examination of a Correction Procedure for the Flow Attenuation in Orthogonal Sonic Anemometers     

Takanori Shimizu  Masakazu Suzuki  Akira Shimizu 《Boundary-Layer Meteorology》1999,93(2):227-236

In this study we examine the calibration of wind speed measured by a sonic anemometer, with an orthogonal probe configuration, with regard to the approximation of the flow angle, and the wind-speed dependence of the flow attenuation attributed to the transducer shadow. The flow angle should be calculated by the iterative method when the attenuation is relatively high. For a probe manufactured by Kaijo Co. TR-61C, the wind-speed dependence of the transducer shadow effect is formulated from the results of the wind-tunnel experiment. Assuming the equation is applicable to field observations, significant errors possibly remain especially when the wind speed is low, and /or the angle between the flow vector and the sonic path is small, if the wind-speed dependence in measurement errors is neglected.  相似文献   

Utilization of underground spaces in urban areas: Urban geo-grid plan     

Noriharu Miyake  Atsushi Denda 《Engineering Geology》1993,35(3-4):175-181

Miyake, N. and Denda, A., 1993. Utilization of underground spaces in urban areas: Urban geo-grid plan. In: M. Langer, K. Hoshino and K. Aoki (Editors). Engineering Geology in the Utilization of Underground Space.Eng. Geol., 35: 175–181.

The Urban Geo-grid Plan aims for a systematic and better coexistence of above-ground and underground areas through the utilization of underground space presently not in use, without interfering with existing urban functions. There would be “base points” supporting regional functions which are laid out in a grid connected by “lines”. Base points would consist of “grid points” and “grid stations”, which serve as control centers for grid points, the grid points and grid stations being interconnected by tunnels to form an “underground network”. Normally, a base point would be used for multiple purposes to supplement regional functions which are inadequate, as well as urban functions, and in emergencies, such as earthquake disasters, it would demonstrate information and evacuations functions.  相似文献   

Source of Ground Water in the Deserts of Northern Chile: Evidence of Deep Circulation of Ground Water from the Andes   总被引：3，自引：0，他引：3  

M. Magaritz  R. Aravena  H. Peña  O. Suzuki  A. Grilli 《Ground water》1990,28(4):513-517

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