Lunar gravity field determination using SELENE same-beam differential VLBI tracking data   总被引：2，自引：0，他引：2  

S. Goossens  K. Matsumoto  Q. Liu  F. Kikuchi  K. Sato  H. Hanada  Y. Ishihara  H. Noda  N. Kawano  N. Namiki  T. Iwata  F. G. Lemoine  D. D. Rowlands  Y. Harada  M. Chen 《Journal of Geodesy》2011,85(4):205-228

A lunar gravity field model up to degree and order 100 in spherical harmonics, named SGM100i, has been determined from SELENE and historical tracking data, with an emphasis on using same-beam S-band differential VLBI data obtained in the SELENE mission between January 2008 and February 2009. Orbit consistency throughout the entire mission period of SELENE as determined from orbit overlaps for the two sub-satellites of SELENE involved in the VLBI tracking improved consistently from several hundreds of metres to several tens of metres by including differential VLBI data. Through orbits that are better determined, the gravity field model is also improved by including these data. Orbit determination performance for the new model shows improvements over earlier 100th degree and order models, especially for edge-on orbits over the deep far side. Lunar Prospector orbit determination shows an improvement of orbit consistency from 1-day predictions for 2-day arcs of 6 m in a total sense, with most improvement in the along and cross-track directions. Data fit for the types and satellites involved is also improved. Formal errors for the lower degrees are smaller, and the new model also shows increased correlations with topography over the far side. The estimated value for the lunar GM for this model equals 4902.80080±0.0009 km³/s² (10 sigma). The lunar degree 2 potential Love number k ₂ was also estimated, and has a value of 0.0255 ± 0.0016 (10 sigma as well).  相似文献   

Numerical analysis on seismic response of Shinkansen bridge-train interaction system under moderate earthquakes     

Mitsuo Kawatani  Toshiro Hayashikawa  Takashi Matsumoto 《地震工程与工程振动(英文版)》2011,10(1):85-97

This study is intended to evaluate the influence of dynamic bridge-train interaction (BTI) on the seismic response of the Shinkansen system in Japan under moderate earthquakes. An analytical approach to simulate the seismic response of the BTI system is developed. In this approach, the behavior of the bridge structure is assumed to be within the elastic range under moderate ground motions. A bullet train car model idealized as a sprung-mass system is established. The viaduct is modeled with 3D finite elements. The BTI analysis algorithm is verified by comparing the analytical and experimental results. The seismic analysis is validated through comparison with a general program. Then, the seismic responses of the BTI system are simulated and evaluated. Some useful conclusions are drawn, indicating the importance of a proper consideration of the dynamic BTI in seismic design.  相似文献   

Structural-stratigraphic control on the Umitaka Spur gas hydrates of Joetsu Basin in the eastern margin of Japan Sea   总被引：1，自引：0，他引：1  

Antonio Fernando Menezes Freire  Ryo Matsumoto  Luiz Alberto Santos 《Marine and Petroleum Geology》2011,28(10):1967-1978

Integrated geological, geochemical, and geophysical exploration since 2004 has identified massive accumulation of gas hydrate associated with active methane seeps on the Umitaka Spur, located in the Joetsu Basin on the eastern margin of Japan Sea. Umitaka Spur is an asymmetric anticline formed along an incipient subduction zone that extends throughout the western side of the Japanese island-arc system. Seismic surveys recognized chimney structures that seem strongly controlled by a complex anticlinal axial fault system, and exhibit high seismic amplitudes with apparent pull-up structures, probably due to massive and dense accumulation of gas hydrate. Bottom simulating reflectors are widely developed, in particular within gas chimneys and in the gently dipping eastern flank of the anticline, where debris can store gas hydrates that may represent a potential natural gas resource. The axial fault system, the shape of the anticline, and the carrier beds induce thermogenic gas migration to the top of the structure, and supply gas to the gas hydrate stability zone. Gas reaching the seafloor produces strong seepages and giant plumes in the sea water column.  相似文献   

Occurrence and exploration of gas hydrate in the marginal seas and continental margin of the Asia and Oceania region   总被引：5，自引：0，他引：5  

Ryo Matsumoto  Byong-Jae Ryu  Sung-Rock Lee  Saulwood Lin  Shiguo Wu  Kalachand Sain  Ingo Pecher  Michael Riedel 《Marine and Petroleum Geology》2011,28(10):1751-1767

Supplies of conventional natural gas and oil are declining fast worldwide, and therefore new, unconventional forms of energy resources are needed to meet the ever-increasing demand. Amongst the many different unconventional natural resources are gas hydrates, a solid, ice-like crystalline compound of methane and water formed under specific low temperature and high pressure conditions. Gas hydrates are believed to exist in large quantities worldwide in oceanic regions of continental margins, as well as associated with permafrost regions in the Arctic. Some studies to estimate the global abundance of gas hydrate suggest that the total volume of natural gas locked up in form of gas hydrates may exceed all known conventional natural gas reserves, although large uncertainties exist in these assessments. Gas hydrates have been intensively studied in the last two decades also due to connections between climate forcing (natural and/or anthropogenic) and the potential large volumes of methane trapped in gas hydrate accumulations. The presence of gas hydrate within unconsolidated sediments of the upper few hundred meters below seafloor may also pose a geo-hazard to conventional oil and gas production. Additionally, climate variability and associated changes in pressure-temperature regimes and thus shifts in the gas hydrate stability zone may cause the occurrence of submarine slope failures.Several large-scale national gas hydrate programs exist especially in countries such as Japan, Korea, Taiwan, China, India, and New Zealand, where large demands of energy cannot be met by domestic supplies from natural resources. The past five years have seen several dedicated deep drilling expeditions and other scientific studies conducted throughout Asia and Oceania to understand gas hydrates off India, China, and Korea. This thematic set of publications is dedicated to summarize the most recent findings and results of geo-scientific studies of gas hydrates in the marginal seas and continental margin of the Asia, and Oceania region.  相似文献   

Phytoplankton productivity in the western subarctic gyre of the North Pacific in early summer 2006     

Tetsuichi Fujiki  Kazuhiko Matsumoto  Shuichi Watanabe  Takuji Hosaka  Toshiro Saino 《Journal of Oceanography》2011,67(3):295-303

We deployed a profiling buoy system incorporating a fast repetition rate fluorometer in the western subarctic Pacific and carried out time-series observations of phytoplankton productivity from 9 June to 15 July 2006. The chlorophyll a (Chl a) biomass integrated over the euphotic layer was as high as 45–50 mg Chl a m⁻² in the middle of June and remained in the 30–40 mg Chl a m⁻² range during the rest of observation period; day-to-day variation in Chl a biomass was relatively small. The daily net primary productivity integrated over the euphotic layer ranged from 144 to 919 mg C m⁻² day⁻¹ and varied greatly, depending more on insolation rather than Chl a biomass. In addition, we found that part of primary production was exported to a 150-m depth within 2 days, indicating that the variations in primary productivity quickly influenced the organic carbon flux from the upper ocean. Our results suggest that the short-term variability in primary productivity is one of the key factors controlling the carbon cycle in the surface ocean in the western subarctic Pacific.  相似文献   

Recent hydrological and geochemical research for earthquake prediction in Japan   总被引：1，自引：0，他引：1  

Norio Matsumoto  Naoji Koizumi 《Natural Hazards》2013,69(2):1247-1260

Hydrological and geochemical studies for earthquake prediction in Japan during the last two decades are reviewed. Following the 1995 Hyogo-ken Nanbu (Kobe) earthquake, the central approach to research on earthquake prediction was modified. Instead of precursory detection, emphasis was placed on understanding the entire earthquake cycle. Moreover, the prediction program for the anticipated Tokai earthquake was revised in 2003 to include the detection of preslip-related precursors. These changes included the promotion of the following hydrological and geochemical studies for earthquake prediction: (1) development and/or application of statistical methods to extract small fluctuations from hydrological/geochemical data, (2) evaluation of the detectability of preslip-related anomalies in terms of groundwater levels in wells in the Tokai region, and (3) establishment of a new groundwater and borehole strain observation network for Nankai and Tonankai earthquake prediction research. The following basic geochemical studies were carried out: (1) development of a new monitoring system using a quadrupole mass spectrometer, (2) experimental studies on hydrogen generation by the grinding of rock and crystal powders, (3) comprehensive monitoring of groundwater gas and precise crustal deformation, and (4) mantle-derivative helium observation to compare with seismic velocity structures and the distribution of non-volcanic tremors. Moreover, hydrological and geochemical investigations related to the evolution of fault zones were introduced within the framework of fault zone drilling projects.  相似文献   

Investigation of the sliding behavior between steel and mortar for seismic applications in structures     

Jason McCormick  Takuya Nagae  Masahiro Ikenaga  Peng‐Cheng Zhang  Mika Katsuo  Masayoshi Nakashima 《地震工程与结构动力学》2009,38(12):1401-1419

The friction developed between a steel base plate and a mortar base contributes shear resistance to the building system during a seismic event. In order to investigate the possible sliding behavior between the base plate and the mortar, a shake table study is undertaken using a large rigid mass supported by steel contact elements which rest on mortar surfaces connected to the shake table. Horizontal input accelerations are considered at various magnitudes and frequencies. The results provide a constant friction coefficient during sliding with an average value of approximately 0.78. A theoretical formulation of the friction behavior is also undertaken. The theoretical equations show that the sliding behavior is dependent on the ratio of the friction force to the input force. The addition of vertical accelerations to the system further complicates the sliding behavior as a result of the varying normal force. This results in a variable friction resistance which is a function of the amplitude, phase, and frequency of the horizontal and vertical input motions. In general, this study showed a consistent and reliable sliding behavior between steel and mortar. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

真鲷饵料生物褶皱臂尾轮虫和眼点拟微绿藻的大量培养     

刘新富  雷霁霖  刘忠强  柳学周 《海洋科学》2000,24(5):47-51

于1992～1994年 ,在中国水科院黄海水产研究所小麦岛试验基地(青岛)进行的“中日合作真鲷增殖放流项目”执行期间 ,对真鲷饵料生物———眼点拟微绿藻 (Nannochloropsisoculata)和L型褶皱臂尾轮虫 (Branchionus plicatilis)进行了大量培养。眼点拟微绿藻的平均接种密度为1211.3×104个/ml,经5～6d的室内或室外露天培养即可达到平均为2341.0×104 个/ml的收获密度 ;采用眼点拟微绿藻和新鲜面包酵母作为混合饵料 ;褶皱臂尾轮虫 (L型 )培养3～4d即可由接种时平均密度148.0个/ml,增长至平均216.8个/ml的采收密度。眼点拟微绿藻和轮虫的日间增殖密度分别是12.8 %和26.6 %。每生产108个褶皱臂尾轮虫需要消耗0.73m3眼点拟微绿藻 (密度为2000×104/ml)和790.8g 鲜面包酵母。采用此法 ,作者连续3a成功地为每年百万尾以上真鲷苗种提供了足够的生物饵料。总结3a苗种培育和生物饵料培养之间的关系 ,作者认为 ,大规模稳定生产海水鱼类苗种时,育苗与饵料生物培养 (褶皱臂尾轮虫和眼点拟微绿藻 )水体的合理比例应为1∶1～1.5∶3。  相似文献   

Improved Method for Calculating Anthropogenic CO2 in the Upper Layer of the North Pacific Subtropical Gyre along 175°E     

Yoshiyuki Takahashi  Eiji Matsumoto  Yutaka W. Watanabe 《Journal of Oceanography》1999,55(6):717-729

Seawater samples were collected in the North Pacific along 175°E during a cruise of the Northwest Pacific Carbon Cycle Study (NOPACCS) program in 1994. Many properties related to the carbonate system were analyzed. By using well-known ratios to correct for chemical changes in seawater, the CO₂ concentration at a given depth was back calculated to its initial concentration at the time when the water left the surface in winter. We estimated sea-surface CO₂ and titration alkalinity (TA) in present-day winter, from which we evaluated the degree of air-sea CO₂ disequilibrium in winter was. Using a correction factor for air-sea CO₂ disequilibrium in winter, we reconstructed sea-surface CO₂ in pre-industrial times. The difference between the back-calculated initial CO₂ and sea-surface CO₂ in pre-industrial times should correspond to anthropgenic CO₂ input. Although the mixing of different water masses may cause systematic error in the calculation, we found that the nonlinear effect induced by the mixing of different water masses was negligible in the upper layer of the North Pacific subtropical gyre along 175°E. The results of our improved method of assessing the distribution of anthropogenic CO₂ in that region show marked differences from those obtained using the previous back-calculation method.  相似文献   

Morphodynamics of a bedrock‐alluvial meander bend that incises as it migrates outward: approximate solution of permanent form          下载免费PDF全文

Takuya Inoue  Gary Parker  Colin P. Stark 《地球表面变化过程与地形》2017,42(9):1342-1354

In meandering rivers cut into bedrock, erosion across a channel cross‐section can be strongly asymmetric. At a meander apex, deep undercutting of the outer bank can result in the formation of a hanging cliff (which may drive hillslope failure), whereas the inner bank adjoins a slip‐off slope that connects to the hillslope itself. Here we propose a physically‐based model for predicting channel planform migration and incision, point bar and slip‐off slope formation, bedrock abrasion, the spatial distribution of alluvial cover, and adaptation of channel width in a mixed bedrock‐alluvial channel. We simplify the analysis by considering a numerical model of steady, uniform bend flow satisfying cyclic boundary conditions. Thus in our analysis, ‘sediment supply’, i.e. the total volume of alluvium in the system, is conserved. In our numerical simulations, the migration rate of the outer bank is a specified parameter. Our simulations demonstrate the existence of an approximate state of dynamic equilibrium corresponding to a near‐solution of permanent form in which a bend of constant curvature, width, cross‐sectional shape and alluvial cover distribution migrates diagonally downward at constant speed, leaving a bedrock equivalent of a point bar on the inside of the bend. Channel width is set internally by the processes of migration and incision. We find that equilibrium width increases with increasing sediment supply, but is insensitive to outer bank migration rate. The slope of the bedrock point bar varies inversely with both outer bank migration rate and sediment supply. Although the migration rate of the outer bank is externally imposed here, we discuss a model modification that would allow lateral side‐wall abrasion to be treated in a manner similar to the process of bedrock incision. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献