Seismological monitoring on the 2003 Tokachi-oki earthquake, derived from off Kushiro permanent cabled OBSs and land-based observations     

Tomoki Watanabe  Hiroaki Takahashi  Masayoshi Ichiyanagi  Muneo Okayama  Masamitsu Takada  Riyo Otsuka  Kenji Hirata  Shigehiko Morita  Minoru Kasahara  Hitoshi Mikada   《Tectonophysics》2006,426(1-2):107

Japan Marine Science and Technology Center installed a cabled geophysical observatory system off Kushiro, Hokkaido Island in July 1999. This observatory system comprises three ocean bottom seismographs (OBSs), two tsunami gauges, and a geophysical/geochemical monitoring system. 4 years and 2 months after the installation, a megathrust earthquake (the 2003 Tokachi-Oki earthquake, 26th September in Japan Standard Time (JST), M_JMA 8.0) occurred along a plate boundary underneath a forearc basin where the system is located. The system recorded clear unsaturated seismograms just at 28.6 km from the epicenter. This paper demonstrates advantages brought by the cabled observatory to record the megathrust earthquake showing how earthquake detectability is improved dramatically combining permanent OBS and land-based observations around the region, and importance of the in situ monitoring on the seismogenic zone. In the present study, processing OBSs and land-based network together, and comparing magnitudes of common observed earthquakes with national authorized network, event detection level improved down to M 1.5, which is much lower than the previously designed as down to M  2. Comparing detection level before and after installing OBSs, we found dramatic improvement of the earthquake detection level in the interesting region. Real-time continuous observations of microearthquakes since 1999 have brought us tremendous findings. First, a seismic quiescence started about 10 days before the 2003 Tokachi-Oki earthquake. Second, aftershock distribution is not uniform over the focal area and can be divided into several sub-regions, which might indicate an existence of several asperities. We think that the geophysical observations helped to understand the initiation process of the rupture of the 2003 Tokachi-Oki earthquake and that observations including seismological, geodynamic, hydrogeological, and the other multidisciplinary observations would provide a clue to future understanding of seismogenic processes at subduction zones.  相似文献   

New discoveries in dynamics of an M8 earthquake-phenomena and their implications from the 2003 Tokachi-oki earthquake using a long term monitoring cabled observatory   总被引：1，自引：0，他引：1  

Hitoshi Mikada  Kyohiko Mitsuzawa  Hiroyuki Matsumoto  Tomoki Watanabe  Shigehiko Morita  Riyo Otsuka  Hiroko Sugioka  Toshitaka Baba  Eiichiro Araki  Kiyoshi Suyehiro 《Tectonophysics》2006,426(1-2):95

At the 2003 Tokachi-oki earthquake of M8, seafloor phenomena such as a generation process of tsunami, seafloor uplifts, turbidity current, etc., were observed using a cabled observatory installed on the seafloor. The turbidity current was observed as a benthic storm caused presumably by the mainshock. The seafloor uplifts were observed at the mainshock and continuously after the mainshock. The uplifts were 0.35, 0.37, and 0.12 m for epicentral distances of 25.5, 31.4, and 81.7 km, respectively. After the mainshock, a continuous uplift of the seafloor is observed at all three pressure gauge locations indicating that there was a change in the state of friction on the plate boundary interface by the mainshock. In this paper, we first show what was observed using the cabled observatory installed right above the focal area of the earthquake, and then we discuss to summarize these phenomena associated with the earthquake, its possible causes, and future directions in long term monitoring of seismogenic processes.  相似文献   

Small-Amplitude Disturbances In A Radiating And Scattering Grey Medium Ii. Solutions Of Given Real Wave Number <Emphasis Type="BoldItalic">k</Emphasis>     

Noboru?KanekoEmail author  Kazuhiko?Morita  Tetsuya?Satoh  Kimitake?Hayasaki 《Astrophysics and Space Science》2005,299(3):263-306

We study the fundamental modes of radiation hydrodynamic waves arising from one-dimensional small-amplitude initial fluctuations with wave number k in a radiating and scattering grey medium using the Eddington approximation. The dispersion relation analyzed is the same as that of Paper I (Kaneko et al., 2000), but is solved as a quintic in angular frequency ω while a quadratic in k ² in Paper I. Numerical results reveal that wave patterns of five solutions are distinguished into three types of the radiation-dominated and type 1 and type 2 matter-dominated cases. The following wave modes appear in our problem: radiation wave, conservative radiation wave, entropy wave, Newtonian-cooling wave, opacity-damped and cooling-damped waves, constant-volume and constant-pressure diffusion modes, adiabatic sound wave, cooling-damped and drag–force-damped isothermal sound waves, isentropic radiation-acoustic wave, and gap mode. The radiation-dominated case is characterized by the gap between the isothermal sound and isentropic radiation-acoustic speeds within which there is not any acoustic wave propagating with real phase speed. One of the differences between type 1 and type 2 matter-dominated cases is the connectivity of the constant-volume diffusion mode, which originates from the radiative mode in the former case, while from the Newtonian-cooling wave in the latter case. Analytic solutions are derived for all wave modes to discuss their physical significance. The criterion, which distinguishes between radiation-dominated and type 1 matter-dominated cases, is given by Γ₀ = 9, where Γ₀ = C _p ^(tot)/C _V ^(tot) is the ratio of total specific heats at constant pressure and constant volume. Waves in a scattering grey medium are also analyzed, which provides us some hints for the effects of energy and momentum exchange between matter and radiation.  相似文献   

Extending Lagrangian perturbation theory to a fluid with velocity dispersion     

Masaaki Morita  Takayuki Tatekawa 《Monthly notices of the Royal Astronomical Society》2001,328(3):815-828

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Observations of Flares and Active Regions from Yohkoh, and Magnetodynamic Models Explaining Them     

Y. Uchida  S. Hirose  S. Morita  M. Torii  T. Tanaka  T. Yabiku  T. Miyagoshi  S. Uemura  T. Yamaguchi 《Astrophysics and Space Science》1998,264(1-4):145-169

We discuss here some of the new aspects about solar flares and active regions found by the Solar X-ray Satellite Yohkoh, by taking advantage of the wider dynamic range and higher cadence observations with higher spatial resolution compared with the previous satellites. Those new aspects have lead us to new ways of understandings, with contradictions to the previous views about flares and active regions that are widely conceived for a long time. We give some models that explain those newly revealed observational results. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Thermolability of glycolysis enzymes from a psychrophilic marine bacterium     

Richard Y. Morita  Paul F. Mathemeier 《Journal of Oceanography》1977,33(5):254-258

Cell extracts ofVibrio marinus MP-1 grown at 15°C and suspended in either tris-HCl buffer or NaCl were compared for heat lability of hexokinase, glucose phosphate isomerase, and aldolase. In tris buffer glucose phosphate isomerase and aldolase lost 50 per cent activity after one hour at low thermal exposures of 34°C and 28°C, respectively. Complete loss of enzyme activity occurred at 36°C and 34°C, respectively. Hexokinase suspended in tris buffer lost all activity above 17°C. The cell extracts suspended in 3.6 per cent NaCl were more heat stable and the enzymes lost 50 per cent activity after exposure between 31°C and 35°C. The enzymes lost all activity on thermal exposure of 33°C to 38°C in the presence of NaCl.  相似文献   

Effects of environmental parameters of low temperature and hydrostatic pressure on L-serine deamination byVibrio marinus     

Lawrence J. Albright  Richard Y. Morita 《Journal of Oceanography》1972,28(2):63-70

Vibrio marinus, an obligately psychrophilic marine bacterium, deaminated nine of 17 amino acids tested with both L-glutamine and L-serine displaying the greatest deamination rates.The L-serine deamination temperature response of washed cells depended upon the growth temperature ofV. marinus MP-1. Cells grown at 15°C displayed optimum activity at 40°C, and a shoulder at 15°C, whereas 4°C grown cells revealed two temperature optima, one at 38 and the other at 11°C, this suggests that the 4°C grown cells are physiologically different than the 15°C grown cells.It is suggested that these peaks in deamination of L-serine at different temperatures might be due to the loss of permeability control above the maximum growth temperature (20°C) of the organism.Hydrostatic pressure stimulated or suppressed L-serine deamination by washed cells depending upon the temperature at which the cells were grown and the incubation temperature of the reaction mixture. Cells grown at 15 or 4°C had deamination stimulated under pressure in the following cases: (i) cells grown at 15°C and tested for deamination at 15°C, (ii) cells grown at 4°C and tested at 4°C and (iii) cells grown at 4°C and tested at 15°C. When cells were grown at 15°C and tested at 4°C no stimulation of deamination activity due to pressure was observed.  相似文献   

A review of Pacific salmon hatchery programmes on Hokkaido Island, Japan     

Morita  Kentaro; Saito  Toshihiko; Miyakoshi  Yasuyuki; Fukuwaka  Masa-aki; Nagasawa  Toru; Kaeriyama  Masahide 《ICES Journal of Marine Science》2006,63(7):1353-1363

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Detection of high concentrations of 137Cs in Walleye pollock collected in the Sea of Japan     

Morita T  Fujimoto K  Minamisako Y  Yoshida K 《Marine pollution bulletin》2007,54(8):1293-1300

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Regeneration dynamics of iron and nutrients from bay sediment into bottom water of Funka Bay,Japan     

Nanako Hioki  Kenshi Kuma  Yuichiroh Morita  Daichi Miura  Atsushi Ooki  Seiji Tanaka  Hiroji Onishi  Tetsuya Takatsu  Naoto Kobayashi  Yoshihiko Kamei 《Journal of Oceanography》2015,71(6):703-714

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