Possible change in distribution of seaweed, Sargassum horneri, in northeast Asia under A2 scenario of global warming and consequent effect on some fish     

Teruhisa Komatsu  Masahiro Fukuda  Atsuko Mikami  Shizuha Mizuno  Attachai Kantachumpoo  Hideaki Tanoue  Michio Kawamiya 《Marine pollution bulletin》2014

Global warming effects on seaweed beds are already perceptible. Their geographical distributions greatly depend on water temperatures. To predict future geographical distributions of brown alga, Sargassum horneri, forming large beds in the northwestern Pacific, we referred to future monthly surface water temperatures at about 1.1° of longitude and 0.6° of latitude in February and August in 2050 and 2100 simulated by 12 organizations under an A2 scenario of global warming. The southern limit of S. horneri distribution is expected to keep moving northward such that it may broadly disappear from Honshu Island, the Chinese coast, and Korean Peninsula in 2100, when tropical Sargassum species such as Sargassum tenuifolium may not completely replace S. horneri. Thus, their forests in 2100 do not substitute those of S. horneri in 2000. Fishes using the beds and seaweed rafts consisting of S. horneri in East China Sea suffer these disappearances.  相似文献   

Earthquake engineering research needs in light of lessons learned from the 2011 Tohoku earthquake     

Masayoshi Nakashima  Oren Lavan  Masahiro Kurata  Yunbiao Luo 《地震工程与工程振动(英文版)》2014,13(1):141-149

Earthquake engineering research and development have received much attention since the first half of the twentieth century. This valuable research presented a huge step forward in understanding earthquake hazard mitigation, which resulted in appreciable reduction of the effects of past earthquakes. Nevertheless, the 2011 Tohoku earthquake and the subsequent tsunami resulted in major damage. This paper presents the timeline of earthquake mitigation and recovery, as seen by the authors. Possible research directions where the authors think that many open questions still remain are identified. These are primarily based on the important lessons learned from the 2011 Tohoku earthquake.  相似文献   

Cross-scale coupling at a perpendicular collisionless shock     

Takayuki Umeda  Masahiro Yamao 《Planetary and Space Science》2011,59(7):449-455

A full particle simulation study is carried out on a perpendicular collisionless shock with a relatively low Alfven Mach number (M_A = 5). Recent self-consistent hybrid and full particle simulations have demonstrated ion kinetics are essential for the non-stationarity of perpendicular collisionless shocks, which means that physical processes due to ion kinetics modify the shock jump condition for fluid plasmas. This is a cross-scale coupling between fluid dynamics and ion kinetics. On the other hand, it is not easy to study cross-scale coupling of electron kinetics with ion kinetics or fluid dynamics, because it is a heavy task to conduct large-scale full particle simulations of collisionless shocks. In the present study, we have performed a two-dimensional (2D) electromagnetic full particle simulation with a “shock-rest-frame model”. The simulation domain is taken to be larger than the ion inertial length in order to include full kinetics of both electrons and ions. The present simulation result has confirmed the transition of shock structures from the cyclic self-reformation to the quasi-stationary shock front. During the transition, electrons and ions are thermalized in the direction parallel to the shock magnetic field. Ions are thermalized by low-frequency electromagnetic waves (or rippled structures) excited by strong ion temperature anisotropy at the shock foot, while electrons are thermalized by high-frequency electromagnetic waves (or whistler mode waves) excited by electron temperature anisotropy at the shock overshoot. Ion acoustic waves are also excited at the shock overshoot where the electron parallel temperature becomes higher than the ion parallel temperature. We expect that ion acoustic waves are responsible for parallel diffusion of both electrons and ions, and that a cross-scale coupling between an ion-scale mesoscopic instability and an electron-scale microscopic instability is important for structures and dynamics of a collisionless perpendicular shock.  相似文献   

Reaction-induced grain boundary cracking and anisotropic fluid flow during prograde devolatilization reactions within subduction zones     

Atsushi?OkamotoEmail author  Hiroyuki?Shimizu  Jun-ichi?Fukuda  Jun?Muto  Takamoto?Okudaira 《Contributions to Mineralogy and Petrology》2017,172(9):75

Devolatilization reactions during prograde metamorphism are a key control on the fluid distribution within subduction zones. Garnets in Mn-rich quartz schist within the Sanbagawa metamorphic belt of Japan are characterized by skeletal structures containing abundant quartz inclusions. Each quartz inclusion was angular-shaped, and showed random crystallographic orientations, suggesting that these quartz inclusions were trapped via grain boundary cracking during garnet growth. Such skeletal garnet within the quartz schist formed related to decarbonation reactions with a positive total volume change (?V _t > 0), whereas the euhedral garnet within the pelitic schists formed as a result of dehydration reaction with negative ?V _t values. Coupled hydrological–chemical–mechanical processes during metamorphic devolatilization reactions were investigated by a distinct element method (DEM) numerical simulation on a foliated rock that contained reactive minerals and non-reactive matrix minerals. Negative ?V _t reactions cause a decrease in fluid pressure and do not produce fractures within the matrix. In contrast, a fluid pressure increase by positive ?V _t reactions results in hydrofracturing of the matrix. This fracturing preferentially occurs along grain boundaries and causes episodic fluid pulses associated with the development of the fracture network. The precipitation of garnet within grain boundary fractures could explain the formation of the skeletal garnet. Our DEM model also suggests a strong influence of reaction-induced fracturing on anisotropic fluid flow, meaning that dominant fluid flow directions could easily change in response to changes in stress configuration and the magnitude of differential stress during prograde metamorphism within a subduction zone.  相似文献   

An overview of Task 6 of the Äspö Task Force: modelling groundwater and solute transport: improved understanding of radionuclide transport in fractured rock     

David Hodgkinson  Hakim Benabderrahmane  Mark Elert  Aimo Hautojärvi  Jan-Olof Selroos  Yasuharu Tanaka  Masahiro Uchida 《Hydrogeology Journal》2009,17(5):1035-1049

An overview is presented of a 4-year study by the Äspö Task Force on Modelling of Groundwater Flow and Transport of Solutes, whose primary aim was to build a bridge between the approaches used for site characterisation (SC) and performance assessment (PA) associated with nuclear waste repositories. Eleven modelling teams representing six national radioactive waste organisations participated in eight modelling exercises whose objectives were: to assess simplifications used in PA models; to determine how, and to what extent, experimental tracer and flow experiments can constrain the range of parameters used in PA models; to support the design of SC programmes to assure that the results have optimal value for PA calculations; and to improve the understanding of site-specific flow and transport behaviour at different scales using SC models. The modelling tasks were concerned with flow and transport through single and multiple near-planar features on SC and PA timescales, including the diffusion of solutes into multiple immobile zones adjacent to fracture surfaces. In general, tracer tests provide only limited quantitative constraints on retention parameter values relevant to PA but nevertheless provide insight about the flow and transport processes, which is a key element of the bridge between SC and PA.  相似文献   

A new algorithm for distance cartogram construction     

Eihan Shimizu 《International journal of geographical information science》2013,27(11):1453-1470

A distance cartogram is a diagram that visualizes the proximity indices between points in a network, such as time–distances between cities. The Euclidean distances between the points on the distance cartogram represent the given proximity indices. This is a useful visualization tool for the level of service of transport, e.g. difference in the level of service between regions or points in a network and its improvement in the course of time. The two previously proposed methods—multidimensional scaling (MDS) and network time–space mapping—have certain advantages and disadvantages. However, we observe that these methods are essentially the same, and the merits of both these methods can be combined to formulate a generalized solution. In this study, we first formulate the time–space mapping problem, which includes the key features of both of the above stated methods, and propose a generalized solution. We then apply this solution to the time–distances of Japan's railway networks to confirm its applicability.  相似文献   

Verification of net primary production estimation method in the Mongolian Plateau using landsat ETM+data     

Xiong Yan  Kanako Muramatsu  Masahiro Hirata  Kazato Oishi  Ichirow Kaihotsu  Tamio Takamura 《地球空间信息科学学报》2013,16(2):117-122

We plan to estimate global net primary production (NPP) of vegetation using the Advanced Earth Observing Satellite-II (ADEOS-II) Global Imager (GLI) multi-spectral data. We derive an NPP estimation algorithm from ground measurement data on temperate plants in Japan. By the algorithm, we estimate NPP using a vegetation index based on pattern decomposition (VIPD) for the Mongolian Plateau. The VIPD is derived from Landsat ETM+multi-spectral data, and the resulting NPP estimation is compared with ground data measured in a semi-arid area of Mongolia. The NPP estimation derived from satellite remote sensing data agrees with the ground measurement data within the error range of 15% when all above-ground vegetation NPP is calculated for different vegetation classifications.  相似文献   

Anomalous change in atmospheric radon concentration sourced from broad crustal deformation: A case study of the 1995 Kobe earthquake     

Yumi Yasuoka  Yusuke Kawada  Yasutaka Omori  Hiroyuki Nagahama  Tetsuo Ishikawa  Shinji Tokonami  Masahiro Hosoda  Tetsuo Hashimoto  Masaki Shinogi 《Applied Geochemistry》2012

Before the Kobe earthquake, an anomalous increase in atmospheric Rn concentration was observed. By separating the measured concentration of atmospheric Rn into three components according to the distance from the monitoring station, the variation of Rn exhalation rate can be estimated for the respective area using the daily minimum and maximum concentrations. The mean rate of Rn exhalation gradually increased in an area of 20 km around the monitoring station, becoming five times higher than normal in the period between October 1994 and the date of the earthquake. This area had a large co-seismic displacement of up to 30 cm, which roughly corresponds to the crustal strain of 10⁻⁶-order, and it is considered the main source for the atmospheric Rn prior to the Kobe earthquake. Analyses revealed that the pre-seismic change in the atmospheric Rn concentration exhibited an anomalous pattern which would yield information on the spatial distribution of the mechanical response of the ground.  相似文献   

A tribute to Ei Horikoshi (1932–2009)     

Masaaki Shimizu  Shigeru Otoh  Nigel J. Cook 《Resource Geology》2012,62(4):327-328

  相似文献   

Weathering mechanisms and their effects on landsliding in pelitic schist     

Shintaro Yamasaki  Masahiro Chigira 《地球表面变化过程与地形》2011,36(4):481-494

Physical, chemical, and mineralogical analyses of undisturbed drill cores of pelitic schist from a landslide area in Japan clarified the mechanisms of chemical weathering of pelitic schist. Oxidizing surface water percolates downward and reaches an oxidation front, where chlorite is altered to Al‐vermiculite, graphite and pyrite are oxidized and depleted, and goethite precipitates. Oxidation of pyrite also occurs just below the oxidation front, probably by ferric iron. Pyrite oxidation yields sulphuric acid, which penetrates further downward, interacting with and weakening the rocks. In addition to this chemical weakening, stress release and shearing along schistosities form an incipient shear zone, which propagates to a sliding zone that forms the rupture surface of a landslide. Once a sliding zone has developed, it inhibits downward groundwater flow across it because of its low permeability, slowing the downward propagation of the weathering zone until this filtration barrier is broken by landslide movement. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献