Quasi-static slip on the plate boundary associated with the 2003 M8.0 Tokachi-oki and 2004 M7.1 off-Kushiro earthquakes, Japan     

Naoki Uchida  Satoshi Yui  Satoshi Miura  Toru Matsuzawa  Akira Hasegawa  Yoshinobu Motoya  Minoru Kasahara 《Gondwana Research》2009,16(3-4):527-533

We analyzed small repeating earthquakes recorded over a 13-year period and GPS data recorded over an 8-month period to estimate interplate quasi-static slip associated with the 2003 Tokachi-oki earthquake (M8.0) and the 2004 off-Kushiro earthquake (M7.1). The repeating-earthquake analysis revealed that the slip rate near the source region of the Tokachi-oki earthquake was relatively low (< 5 cm/year) prior to the earthquake; however, in the last 3 years leading up to the event, a minor acceleration in slip occurred upon the deeper extension of the coseismic slip area of the earthquake. Repeating-earthquake and GPS data indicate that large amounts of afterslip occurred around the rupture area following the earthquake; the afterslip mainly propagated to the east of the coseismic slip area. We also infer that the occurrence of the 2004 off-Kushiro earthquake, located about 100 km northeast of the epicenter of the Tokachi-oki earthquake, was advanced by the afterslip associated with the Tokachi-oki earthquake.  相似文献   

Evaporation metamorphism of primitive dust material in the early solar nebula     

Akihiko Hashimoto  Mineo Kumazawa  Naoki Onuma 《Earth and Planetary Science Letters》1979,43(1):13-21

An evaporation experiment on matrix material of the Murchison (C2) meteorite up to 1900°C in vacuo has revealed the evaporation sequence of primitive dust material and the associated evolution of residual solid phases from hydrous silicates through magnesium silicates and iron-metal to calcium-aluminum oxides. The comparison with primitive meteorites suggests that the evaporation metamorphism coupled with the re-condensation may have played an important role in the generation of diverse primitive meteorites in the early solar nebula.  相似文献   

A classification of meteorites based on oxygen isotopes     

Robert N. Clayton  Naoki Onuma  Toshiko K. Mayeda 《Earth and Planetary Science Letters》1976,30(1):10-18

On the basis of¹⁸O/¹⁶O and¹⁷O/¹⁶O ratios, meteorites and planets can be grouped into at least six categories, as follows: (1) the terrestrial group, consisting of the earth, moon, differentiated meteorites and enstatite chondrites; (2) types L and LL ordinary chondrites; (3) type H ordinary chondrites; (4) anhydrous minerals of C2, C3, C4 carbonaceous chondrites; (5) hydrous matrix minerals of C2 carbonaceous chondrites; (6) the ureilites. Objects of one category cannot be derived by fractionation or differentiation from the source materials of any other category.  相似文献   

On the excitation of resonant double Kelvin waves in the Barents Sea Opening     

Yoshie Kasajima  Aleksey Marchenko 《Polar research》2001,20(2):241-248

In the northern Barents Sea Opening (BSO) the K₁ tidal energy is predominant in the diurnal tidal frequency band, suggesting the generation of a topographic wave with the K₁ tidal frequency. Tidal energy of the K₁ component becomes strong where bottom topography undulates in the BSO and the scale of the undulation is close to the wavelength of the K₁ wave. An analytical model is developed to investigate the energy enhancement mechanism of the tidally induced topographic wave due to a resonance between tidal current, a topographic wave and periodic topography. The wave excited by the resonance is identified as a resonant double Kelvin wave (DKW) and the significant K₁ energy in the BSO could be due to the excitation of the resonant DKW.  相似文献   

Dynamic loading test and simulation analysis of full‐scale semi‐active hydraulic damper for structural control     

Naoki Niwa  Takuji Kobori  Motoichi Takahashi  Hiroshi Midorikawa  Narito Kurata  Takayuki Mizuno 《地震工程与结构动力学》2000,29(6):789-812

A semi‐active hydraulic damper (SHD) for a semi‐active damper system, which is useful for practical structural control especially for large earthquakes, has been developed. Its maximum damping force is set to 1 or 2 MN, and it is controlled by only 70 W of electric power. An SHD with a maximum damping force of 1 MN was applied to an actual building in 1998. This paper first presents the results of a dynamic loading test to confirm the control performance of the SHD. Next, an analytical model of SHDs (SHD model) is constructed with the same concept for two kinds of SHDs based on the test results. Through simulation analyses of the test results using the proposed SHD model, the dynamic characteristics of the SHD can be well represented within practical conditions. Simulation analyses are also carried out using a simple structure model with the SHD model. It is shown that this SHD model can be used to precisely evaluate the control effect of the semi‐active damper system and is useful in practical SHD design under the applied conditions. Copyright © 2000 John Wiley & Sons, Ltd.  相似文献   

Geogrid-based countermeasures against scour behind coastal dikes under tsunami overflow     

Naoki Takegawa  Toshinori Kawabata 《Marine Georesources & Geotechnology》2020,38(1):64-72

Abstract

Following the Great East Japan Earthquake, a massive tsunami caused serious damage to coastal dikes. Local scour at the ground behind these dikes reportedly causes dike failures. It is important to reveal the scour process to establish methods for effective scour countermeasures. Herein, we focus on geogrids. To verify this proposal and examine its design, flume-model experiments were performed for non-liquefied and liquefied grounds behind coastal dikes. The results showed that the scour amount and area were reduced drastically when geogrids were present. Geogrids on the sand-bed surface changed the direction of overflow water. Thus, a scour hole developed away from a coastal dike model. Furthermore, geogrids exerted a scour-reduction effect even during liquefaction.  相似文献   

Probing the evolution of early-type galaxies using multicolour number counts and redshift distributions     

Fumiaki Nakata  Kazuhiro Shimasaku  Mamoru Doi  Nobunari Kashikawa  Wataru Kawasaki  Yutaka Komiyama  Sadanori Okamura  Maki Sekiguchi  Masafumi Yagi  Naoki Yasuda 《Monthly notices of the Royal Astronomical Society》1999,309(4):L25-L29

We investigate pure luminosity evolution models for early-type (elliptical and S0) galaxies (i.e. no number density change or morphological transition), and examine whether these models are consistent with observed number counts in the B , I and K bands, and redshift distributions of two samples of faint galaxies selected in the I and K bands. The models are characterized by the star formation time-scale τ _SF and the time t _gw when the galactic wind starts to blow, in addition to several other conventional parameters. We find that the single-burst model ( τ _SF=0.1 Gyr and t _gw=0.353 Gyr), which is known to reproduce the photometric properties of early-type galaxies in clusters, is inconsistent with the redshift distributions of early-type galaxies in the field environment, owing to overpredictions of the number of galaxies at z ≳1.4 even with strong extinction which is at work until t _gw. In order for dust extinction to be more effective, we treat τ _SF and t _gw as free parameters, and find that models with τ _SF≳0.5 Gyr and t _gw>1.0 Gyr can be made consistent with both the observed redshift distributions and the number counts, if we introduce strong extinction [ E ( B − V )≥1 as a peak value]. These results suggest that early-type galaxies in the field environment do not have the same evolutionary history as described by the single-burst model.  相似文献   

Dynamics of fatty acids in newly biosynthesized phytoplankton cells and seston during a spring bloom off the west coast of Hokkaido Island, Japan     

K. H. Shin  T. Hama  N. Yoshie  S. Noriki  S. Tsunogai 《Marine Chemistry》2000,70(4):11

¹³C uptake experiments were carried out at a station off the west coast of Hokkaido Island, Japan, during the period between late winter and spring bloom in 1997. The composition of newly biosynthesized particulate fatty acids was determined using a ¹³C tracer and gas chromatography/mass spectrometry (¹³C GC/MS), and compared with that of particulate matter (seston). Two fatty acid compositional ratios revealed that diatoms biomass (16:1(n−7)/16:0, ∑C₁₆/∑C₁₈) were strikingly high in new cells compared with seston on 17 April, coinciding with the dominance of fucoxanthin. In this study, the Polyunsaturation Index (a measure of the percentage of C₁₆ fatty acids that are polyunsaturated) in new cells is generally close to that in seston, while there was a notable discrepancy between new cells and seston in surface (10 m) waters on 17 April. This large difference between new cells and seston is ascribed to: (1) an increase of newly synthesized storage lipids (mainly 16:0 and 16:1) induced by nitrogen limitation in the top 10 m of the water column; (2) an addition of earlier synthesized phytoplankton cells (high Polyunsaturation Index at logarithmic growth stage) and non-phytoplankton components (detritus and bacteria and zooplankton) into seston. The highest Polyunsaturation Index of C₁₆ fatty acids in seston (33%) occurred at 100 m water depth. This may be caused by “settling planktonic aggregates” or “diatom resting spores”. In the present study, it is reasonable to suggest that the Polyunsaturation Index of C₁₆ fatty acids can be a useful indicator for the ecophysiological state of marine diatom populations.  相似文献   

The 21-cm signature of early relic H ii regions     

Midori Tokutani  Naoki Yoshida  S. Peng Oh  Naoshi Sugiyama 《Monthly notices of the Royal Astronomical Society》2009,395(2):777-780

We calculate the spin temperature and 21-cm brightness of early H  ii regions around the first stars. We use outputs from cosmological radiation-hydrodynamics simulations of the formation and evolution of early H  ii regions. In the pre-re-ionization era, H  ii regions around massive primordial stars have diameters of a few kpc. The gas within the H  ii regions is almost fully ionized, but begins recombining after the central stars die off. The relic H  ii regions are then seen as bright emission sources in hydrogen 21 cm. We make brightness temperature maps of the H  ii regions, accounting for radiative coupling with Lyman α photons in a simplified manner. The spin temperature in the relic H  ii region is close to the gas kinetic temperature, generally several hundred to several thousand degrees. We show that the relic H  ii region can be as bright as  δ T _b∼ 100 mK  in differential temperature against the cosmic microwave background for an angular resolution of subarcseconds. While individual early H  ii patches will not be identified by currently planned radio telescopes, the collective fluctuations from early H  ii regions might imprint signatures in the 21-cm background.  相似文献   

Proton migration in portlandite inferred from activation energy of self-diffusion and potential energy curve of OH bond     

Naoki Noguchi  Keiji Shinoda 《Physics and Chemistry of Minerals》2010,37(6):361-370

A fundamental mechanism on the atomic level for self-diffusion in the proton layer of portlandite, Ca(OH)₂, was investigated by conducting hydrogen–deuterium (H–D) exchange diffusion experiments and by deriving potential energy curves of OH vibrations from optical absorption measurements. Synthetic single crystals of portlandite were used in H–D experiments between 250 and 450°C at 150 MPa. Arrhenius parameters for proton diffusion perpendicular to the c-axis gave a frequency factor of 1.0 × 10⁻¹⁰ m²/s and activation energy of 0.61 eV (58.5 kJ/mol). The activation energy corresponds to the height of the potential barrier between two oxygen atoms across an interlayer. The potential barrier height was also theoretically estimated using the OH potential energy curve (OH-PEC) determined by optical absorption measurements. Experimental and theoretical results suggest that the potential barrier height cannot be simply determined by overlapping two OH-PECs. The potential barrier derived theoretically was 3.11 eV. This is too high for the activation energy of the proton diffusion. It implies that the interaction between a diffusing proton and the vacancy of a proton site, and the shortening of interlayer oxygen distance by thermal vibration reduce the potential barrier.  相似文献