Internal structure of Longmenshan fault zone at Hongkou outcrop,Sichuan,China,that caused the 2008 Wenchuan earthquake   总被引：6，自引：1，他引：5  

Tetsuhiro Togo  Toshihiko Shimamoto 《地震学报(英文版)》2011,(3):249-265

This paper reports the internal structures of the Beichuan fault zone of Longmenshan fault system that caused the 2008 Wenchuan earthquake,at an outcrop in Hongkou,Sichuan province,China.Present work is a part of comprehensive project of Institute of Geology,China Earthquake Administration,trying to understand deformation processes in Longmenshan fault zones and eventually to reproduce Wenchuan earthquake by modeling based on measured mechanical and transport properties.Outcrop studies could be integrate...  相似文献   

Regional climatic effects according to different estimations of biogenic volatile organic compounds during the asian summer monsoon     

Hyung-Jin Kim  Kumiko Takata  Katsunori Tanaka  Ryoji Yamashima  Jun Matsumoto  Kazuyuki Saito  Toshihiko Takemura  Tetsuzo Yasunari 《Asia-Pacific Journal of Atmospheric Sciences》2014,50(4):423-435

A series of 60-year numerical experiments starting from 1851 was conducted using a global climate model coupled with an aerosol-cloud-radiation model to investigate the response of the Asian summer monsoon to variations in the secondary organic aerosol (SOA) flux induced by two different estimations of biogenic volatile organic compound (BVOC) emissions. One estimation was obtained from a pre-existing archive and the other was generated by a next-generation model (the Model of Emissions of Gases and Aerosols from Nature, MEGAN). The use of MEGAN resulted in an overall increase of the SOA production through a higher rate of gasto-particle conversion of BVOCs. Consequently, the atmospheric loading of organic carbon (OC) increased due to the contribution of SOA to OC aerosol. The increase of atmospheric OC aerosols was prominent in particular in the Indian subcontinent and Indochina Peninsula (IP) during the pre- and early-monsoon periods because the terrestrial biosphere is the major source of BVOC emissions and the atmospheric aerosol concentration diminishes rapidly with the arrival of monsoon rainfall. As the number of atmospheric OC particles increased, the number concentrations of cloud droplets increased, but their size decreased. These changes represent a combination of aerosol-cloud interactions that were favorable to rainfall suppression. However, the modeled precipitation was slightly enhanced in May over the oceans that surround the Indian subcontinent and IP. Further analysis revealed that a compensating updraft in the surrounding oceans was induced by the thermally-driven downdraft in the IP, which was a result of surface cooling associated with direct OC aerosol radiative forcing, and was able to surpass the aerosolcloud interactions. The co-existence of oceanic ascending motion with the maximum convective available potential energy was also found to be crucial for rainfall formation. Although the model produced statistically significant rainfall changes with locally organized patterns, the suggested pathways should be considered guardedly because in the simulation results, 1) the BVOC-induced aerosol direct effect was marginal; 2) cloud-aerosol interactions were modeldependent; and 3) Asian summer monsoons were biased to a nonnegligible extent.  相似文献   

Internal structure of Longmenshan fault zone at Hongkou outcrop,Sichuan, China,that caused the 2008 Wenchuan earthquake          下载免费PDF全文

Tetsuhiro Togo  Toshihiko Shimamoto  Shengli Ma  Xueze Wen  Honglin He 《地震科学（英文版）》2011,24(3):249-265

This paper reports the internal structures of the Beichuan fault zone of Longmenshan fault system that caused the 2008 Wenchuan earthquake, at an outcrop in Hongkou, Sichuan province, China. Present work is a part of comprehensive project of Institute of Geology, China Earthquake Administration, trying to understand deformation processes in Longmenshan fault zones and eventually to reproduce Wenchuan earthquake by modeling based on measured mechanical and transport properties. Outcrop studies could be integrated with those performed on samples recovered from fault zone drilling, during the Wenchuan Earthquake Fault Scientific Drilling (WFSD) Project, to understand along-fault and depth variation of fault zone properties. The hanging wall side of the fault zone consists of weakly-foliated, clayey fault gouge of about 1 m in width and of several fault breccia zones of 30–40 m in total width. We could not find any pseudotachylite at this outcrop. Displacement during the Wenchuan earthquake is highly localized within the fault gouge layer along narrower slipping-zones of about 10 to 20 mm in width. This is an important constraint for analyzing thermal pressurization, an important dynamic weakening mechanism of faults. Overlapping patterns of striations on slickenside surface suggest that seismic slip at a given time occurred in even narrower zone of a few to several millimeters, so that localization of deformation must have occurred within a slipping zone during coseismic fault motion. Fault breccia zones are bounded by thin black gouge layers containing amorphous carbon. Fault gouge contains illite and chlorite minerals, but not smectite. Clayey fault gouge next to coseismic slipping zone also contains amorphous carbon and small amounts of graphite. The structural observations and mineralogical data obtained from outcrop exposures of the fault zone of the Wenchuan earthquake can be compared with those obtained from the WFSD-1 and WFSD-2 boreholes, which have been drilled very close to the Hongkou outcrop. The presence of carbon and graphite, observed next to the slipping-zone, may affect the mechanical properties of the fault and also provide useful information about coseismic chemical changes.  相似文献   

Detection of small earthquakes along the Pacific-Antarctic Ridge from T-waves recorded by abyssal ocean-bottom observatories     

Aki Ito  Hiroko Sugioka  Daisuke Suetsugu  Hajime Shiobara  Toshihiko Kanazawa  Yoshio Fukao 《Marine Geophysical Researches》2012,33(3):229-238

A number of seismoacoustic T-wave events were observed between January 2003 and January 2004 by broadband ocean-bottom seismometers installed on the French Polynesia seafloor at depths of 4,000?C5,000?m, well below the conjugate depth of the SOFAR channel. Using T-wave arrival times, we located 89 T-wave events along the Pacific-Antarctic Ridge. Among these, 63 events were not detected by land-based seismic observations of the United States Geological Survey (USGS), which was nearly twice the number of earthquakes reported by the USGS in the area during the observation period. We used a simple method to estimate earthquake magnitude from T-wave energy. The magnitudes of the events unidentified by the USGS ranged from 2.3 to 5.5, whereas magnitudes of the earthquakes reported by the USGS ranged from 4.1 to 6.2. Our study suggests that T-wave observations with abyssal ocean-bottom seismometers can improve the detection of small earthquakes and help our understanding of the seismotectonics of remote oceanic areas.  相似文献   

Aerodynamic Scaling for Estimating the Mean Height of Dense Canopies   总被引：1，自引：1，他引：0  

Taro Nakai  Akihiro Sumida  Kazuho Matsumoto  Ken’ichi Daikoku  Shin’ichi Iida  Hotaek Park  Mie Miyahara  Yuji Kodama  Alexander V. Kononov  Trofim C. Maximov  Hironori Yabuki  Toshihiko Hara  Takeshi Ohta 《Boundary-Layer Meteorology》2008,128(3):423-443

We used an aerodynamic method to objectively determine a representative canopy height, using standard meteorological measurements. The canopy height may change if the tree height is used to represent the actual canopy, but little work to date has focused on creating a standard for determining the representative canopy height. Here we propose the ‘aerodynamic canopy height’ h _a as the most effective means of resolving the representative canopy height for all forests. We determined h _a by simple linear regression between zero-plane displacement d and roughness length z ₀, without the need for stand inventory data. The applicability of h _a was confirmed in five different forests, including a forest with a complex canopy structure. Comparison with stand inventory data showed that h _a was almost equivalent to the representative height of trees composing the crown surface if the forest had a simple structure, or to the representative height of taller trees composing the upper canopy in forests with a complex canopy structure. The linear relationship between d and z ₀ was explained by assuming that the logarithmic wind profile above the canopy and the exponential wind profile within the canopy were continuous and smooth at canopy height. This was supported by observations, which showed that h _a was essentially the same as the height defined by the inflection point of the vertical profile of wind speed. The applicability of h _a was also verified using data from several previous studies.  相似文献   

Stick-slip behavior of Indian gabbro as studied using a NIED large-scale biaxial friction apparatus     

Tetsuhiro Togo  Toshihiko Shimamoto  Futoshi Yamashita  Eiichi Fukuyama  Kazuo Mizoguchi  Yumi Urata 《地震科学（英文版）》2015,28(2):97-118

This paper reports stick-slip behaviors of Indian gabbro as studied using a new large-scale biaxial friction apparatus, built in the National Research Institute for Earth Science and Disaster Prevention (NIED), Tsukuba, Japan. The apparatus consists of the existing shaking table as the shear-loading device up to 3, 600 kN, the main frame for holding two large rectangular prismatic specimens with a sliding area of 0.75 m² and for applying normal stresses σ_n up to 1.33 MPa, and a reaction force unit holding the stationary specimen to the ground. The shaking table can produce loading rates v up to 1.0 m/s, accelerations up to 9.4 m/s², and displacements d up to 0.44 m, using four servocontrolled actuators. We report results from eight preliminary experiments conducted with room humidity on the same gabbro specimens at v = 0.1-100 mm/s and σ_n = 0.66-1.33 MPa, and with d of about 0.39 m. The peak and steady-state friction coefficients were about 0.8 and 0.6, respectively, consistent with the Byerlee friction. The axial force drop or shear stress drop during an abrupt slip is linearly proportional to the amount of displacement, and the slope of this relationship determines the stiffness of the apparatus as 1.15×10⁸ N/m or 153 MPa/m for the specimens we used. This low stiffness makes fault motion very unstable and the overshooting of shear stress to a negative value was recognized in some violent stick-slip events. An abrupt slip occurred in a constant rise time of 16-18 ms despite wide variation of the stress drop, and an average velocity during an abrupt slip is linearly proportional to the stress drop. The use of a large-scale shaking table has a great potential in increasing the slip rate and total displacement in biaxial friction experiments with large specimens.  相似文献   

Size distributions of chondrules and dispersed droplets caused by liquid breakup: An application to shock wave conditions in the solar nebula   总被引：1，自引：0，他引：1  

Toshihiko Kadono  Masahiko Arakawa 《Icarus》2008,197(2):621-626

We present the results of an aerodynamic liquid dispersion experiment using initially molten silicate samples. We investigate the threshold of breakup and the size distribution of dispersed droplets. The breakup threshold is consistent with the previous experiments using water and a mixture of water and glycerol. Also, we confirm the previous results that the size distributions of dispersed droplets are represented by an exponential form and that the characteristic size of dispersed droplets is related to the dynamic pressure of high-velocity gas flow. The size distribution has a similar form to that of chondrules, though the experiment is not exactly corresponding to the shock heating models for chondrule formation that consider solid precursors which are molten by the shocks. The experimental results indicate that, if liquid chondrule-precursors were dispersed by high-velocity flow, the dynamic pressure of the flow is ∼10 kPa. A chondrule formation condition in a shock-wave heating model suggests that this pressure can be realized at the regions within ∼1 AU in the minimum solar-nebula mass models. However, if the nebula had a larger mass and gravitational instabilities occurred, this pressure may be realized in the spiral arms at 2-3 AU and chondrules may be formed in asteroid belt.  相似文献   

A Study Of The Atmospheric Boundary Layer Using Radon And Air Pollutants As Tracers     

Toshio Kataoka  Eiji Yunoki  Mitsuo Shimizu  Tadashige Mori  Osamu Tsukamoto  Yukitaka Ohashi  Ken Sahashi  Toshihiko Maitani  Koh’ichi Miyashita  Toru Iwata  Yoko Fujikawa  Akira Kudo  Roger H. Shaw 《Boundary-Layer Meteorology》2001,101(2):131-156

Concentrations of radon ²²²Rn andair pollutants, meteorological parametersnear the surface and vertical profiles of meteorological elements were measured atUchio (Okayama City, Okayama Prefecture, Japan) 12 km north from the coast ofthe Inland Sea of Japan. In the nighttime, the ²²²Rn concentration increased in the case of weak winds, but did not increase as much in the case of moderate or strong winds, as had been expected. In the daytime, the ²²²Rn concentrationheld at a slightly higher than average level for the period from sunrise to about 1100 JST. It is considered that this phenomenon is due to a period of morning calm, that is, a transition period from land breeze to sea breeze.NO, which is sensitive to traffic volume,brought information concerning advection.Oxidant concentrations,which reflect the availability of sunlight,acted in the reverse manner to ²²²Rnconcentrations. Thus, a set of ²²²Rn and air pollutants could provide useful information regarding the local conditions of the atmospheric boundary layer.  相似文献   

Bashi channel,Luzon strait: A hydraulic model experiment of the tidal current     

Sei-ichi Kanari  Toshihiko Teramoto 《Journal of Oceanography》1981,37(1):31-48

Bottom current conditions due to tidal currents in the area of the Bashi Channel, Luzon Strait, are examined using a scaled hydraulic model in a uni-directional flow channel. The geometrical model is scaled in both the similitude of Froude's Number and the similitude of the four-thirds power law of eddy viscosity. The currents obtained from the experiment seem to be consistent in order of magnitude with the estimated currents based on observations made by Offshore Environmental System Ltd. In a quasi-steady tidal phase, formation of a strong core flow is found in the Bashi Channel. It can be explained by a simple theoretical model in which the formation of the strong current is attributed to the submarine topography of the Luzon Strait.  相似文献   

Mobilization and mechanisms of retardation in the Oklo natural reactor zone 2 (Gabon)—inferences from U, REE, Zr, Mo and Se isotopes     

Rgis Bros  Hiroshi Hidaka  Gento Kamei  Toshihiko Ohnuki 《Applied Geochemistry》2003,18(12):1807-1824

Mineralogical and isotopic studies were carried out on the natural nuclear reaction zone 2 from the Oklo deposit to evaluate the mobility of several nuclear reaction products in response to the alteration of the reaction zone and to identify the mechanisms which could retard the transport of released radionuclides. To address these issues, in situ isotopic analyses by SHRIMP and a selective extraction procedure were performed to constrain the structural location of nuclear reaction products (exchangeable and non exchangeable) and their association with mineral phases. The distribution patterns of U, REE, Zr and Mo isotopes reveal that substantial amounts were released from the core and migrated through the hydrothermal alteration halo over metric distances, owing to uraninite dissolution and advective transport by hydrothermal solutions during and soon after criticality. The results emphasize the mobility of Zr at Oklo, this element being often considered as “immobile” during water–rock interactions. The main output is the demonstration of the net effects of sorption and coprecipitation processes. Chlorite and to a lesser extent illite were found to have adsorbed significant amounts of U, REE, Zr (and probably Th) and less sorbing elements such as Mo. Coprecipitation of secondary UO₂ and P-rich coffinite within the alteration halo is also an important means of retardation. The concentration of radionuclides released from the reactor were probably high and they display solubility limited transport behaviour. No retention effect was found for Se in the immediate vicinity of the reactor and this element may have moved farther from its source of production. These results have interesting implications for the evaluation of long-term containment of radionuclides. They provide a simple illustration of the performance of a clay barrier in the uptake of radionuclides by sorption onto clays and reincorporation in secondary U-minerals. This study also demonstrates the robustness of these retention processes over extremely long periods of time.  相似文献