检索结果-南通市图书馆

Robust LS-SVM regression for ore grade estimation in a seafloor hydrothermal sulphide deposit

在线全文

学校读者我要写书评

暂无评论

Acta Oceanologica Sinica 2013年第8期32卷 16-25页

作者： ZHANG Xunan SONG Shiji li jiabiao WU Cheng Department of Automation Tsinghua University Second Institute of Oceanography State Oceanic Administration

Due to the geological complexities of ore body formation and limited borehole sampling, this paper propos- es a robust weighted least square support vector machine （LS-SVM） regression model to solve the ore grade estimation for a seafloor hydrothermal sulphide deposit in Solwara 1, which consists of a large proportion of incomplete samples without ore types and grade values. The standard LS-SVM classification model is applied to identify the ore type for each incomplete sample. Then, a weighted K-nearest neighbor （WKNN） algorithm is proposed to interpolate the missing values. Prior to modeling, the particle swarm optimiza- tion （PSO） algorithm is used to obtain an appropriate splitting for the training and test data sets so as to eliminate the large discrepancies caused by random division. Coupled simulated annealing （CSA） and grid search using 10-fold cross validation techniques are adopted to determine the optimal tuning parameter- s in the LS-SVM models. The effectiveness of the proposed model by comparing with other well-known techniques such as inverse distance weight （IDW）, ordinary kriging （OK）, and back propagation （BP） neural network is demonstrated. The experimental results show that the robust weighted LS-SVM outperforms the other methods, and has strong predictive and generalization ability.

关键词： weighted LS-SVIVl.grade estimation incomplete samples data division

^(40)Ar/^(39)Ar ages of seamount trachytes from the South China Sea and implications for the evolution of the northwestern sub-basin

在线全文

学校读者我要写书评

暂无评论

Geoscience Frontiers 2015年第4期6卷 571-577页

作者： Xiaohu li jiabiao li Xing Yu Chunsheng Wang Fred Jourdan Key Laboratory of Submarine Geoscience State Oceanic Administration Second Institution of Oceanography State Oceanic Administration Key Laboratory of Marine Ecosystem and Biogeochemistry State Oceanic Administration Western Australian Argon Isotope Facility Department of Applied Geology and Jd L Centre Curtin University

A chronological study of seamount rocks in the South China Sea basin provides a great opportunity to understand the expansion and evolution history of the sea basin. In this paper, we analyzed the ^40Ar/^39Ar age of trachytic samples collected from the Shuangfeng seamounts in the northwestern sub-basin of the South China Sea. The two samples yielded plateau ages of 23.80 ± 0.18 and 23.29 ± 0.22 Ma, respectively, which indicate magmatic activity in late Oligocene which helpful constraints the expansion time of the northwest sub-basin. Previous studies suggested that the northwestern sub-basin and southwestern sub-basin have experienced a relatively consistent expansion in the NW-SE direction followed by a late expansion of the eastern sub-basin. We concluded that the expansion of the northwestern sub-basin began prior to ca. 24 Ma, which also implicated magmatic events of a late or stop expansion of the northwestern sub-basin combined with our results of^40Ar/^39Ar age data and previous geophysical data.

关键词： ^40Ar/^39Ar datingSeamount trachyteNorthwest sub-basinExpansion historySouth China Sea

Rifting characteristics of eastern subbasin of South China Sea and its spreading pattern

在线全文

学校读者我要写书评

暂无评论

Acta Oceanologica Sinica 2002年第1期21卷 77-85页

作者： li jiabiao Jin Xianglong Gao Jinyao Key Laboratory of Submarine Geosciences of State Oceanic Administration Hangzhou 310012China Second Institute of Oceanography State Oceanic AdministrationHangzhou 310012China

With processing and interpretation of 25 000 km full-coverage multibeam swath data fromthe eastern South China Sea, it is found that NE-trending and NW-trending linear morphological features such as scarps, horsts and grabens, govern the central part (14°-17° N) of eastern subbasin. Compared with reflection seismic profiles, these NE-trending linear morpho-structures are considered to be the representation of basement structures on seabed and can be divided into three linear structural zones. The trend of the central zone is NE45°-50° occurring around extinct spreading center, the trend of the second zone is NE70° - 78° on both sides of the central one and the trend of the third zone is about NE60° just on the north of the second one. These three NE-trending linear zones are formed in late-stage NW - SE-trending seafloor spreading of the eastern subbasin along NW-trending linear faults, and respectively correspond to three spreading episodes: 17.0- 19.0 Ma (5d-5e), 19.0 - 21.0 Ma (5e-6a) and 21.0 - 24.2 Ma (6a-6c) based on the contrast of morpho-structures to magnetic lineation anomalies.

关键词： Multibeam echosounding swath topography morpho-structures spreading pattern

Seismic phases from the Moho and its implication on the ultraslow spreading ridge

在线全文

学校读者我要写书评

暂无评论

Acta Oceanologica Sinica 2013年第12期32卷 75-86页

作者： ZHANG Jiazheng ZHAO Minghui QIU Xuelin li jiabiao RUAN Aiguo Key Laboratory of Marginal Sea Geology of Chinese Academy of Sciences South China Sea Institute of OceanologyChinese Academy of Sciences University of Academy of Sciences The Second Institute of Oceanography State Oceanic Administration

The Moho interface provides critical evidence for crustal thickness and the mode of oceanic crust accretion. The seismic Moho interface has not been identified yet at the magma-rich segments （46°-52°E） of the ultra- slow spreading Southwestern Indian Ridge （SWIR）. This paper firstly deduces the characteristics and do- mains of seismic phases based on a theoretical oceanic crust model. Then, topographic correction is carried out for the OBS record sections along Profile Y3Y4 using the latest OBS data acquired from the detailed 3D seismic survey at the SWIR in 2010. Seismic phases are identified and analyzed, especially for the reflected and refracted seismic phases from the Moho. A 2D crustal model is finally established using the ray tracing and travel-time simulation method. The presence of reflected seismic phases at Segment 28 shows that the crustal rocks have been separated from the mantle by cooling and the Moho interface has already formed at zero age. The 2D seismic velocity structure across the axis of Segment 28 indicates that detachment faults play a key role during the processes of asymmetric oceanic crust accretion.

关键词： Moho interface seismic phases ultra-slow spreading ridge 2D crustal structure SouthwesternIndian Ridge (SWIR)

Precollisional tectonics and terrain amalgamation offshore southern Taiwan:Characterizations from reflection seismic and potential field data

在线全文

学校读者我要写书评

暂无评论

Science China Earth Sciences 2007年第6期50卷 897-908页

作者： li ChunFeng ZHOU ZuYi li jiabiao CHEN HuanJiang GENG JianHua li Hui State Key Laboratory of Marine Geology Tongji UniversityShanghai 200092China The Second Institute of Oceanography State Oceanic AdministrationHangzhou 310012China

Sponsored by the Chinese National Fundamental Research and Development Program in 2001,Guang-zhou Marine Geological Survey launched out a long geophysical survey from the northeastern part of the South China Sea (SCS),through the Luzon Arc,to the Huatung Basin and the Gagua Ridge. Based on high-resolution seismic data from this survey,combined with gravimetric and magnetic modeling,a systematic effort is made to the study of the regional geodynamics offshore southern Taiwan. By focusing particularly on precollisional tectonic interactions between adjacent geological units and their tectonic affiliations,this study can help reveal early arc-continent collisional processes that formed the Taiwan orogen. The construction of the Manila accretionary prism and its eastward progressive deformation indicate that the subduction of SCS have experienced multiple phases of increased activity. Active precollisional crustal shortening within the Northern Luzon Trough resulted in tilting of sedimentary layers at angles between 6° and 13°. But the shortening induced by tilting accounts for only a tiny part of regional total crustal compression. The eastern flank of the Luzon Arc appears to be more active than the rest,evidenced by active faulting and folding in the intra-arc basins on the eastern flank. Magnetic modeling/inversion shows that the Luzon Arc may have experienced multiple phases of magmatic activities,causing lateral magnetic inhomogeneity. Bouguer gravity anomalies and gravity modeling indicate that the Huatung Basin has anomalously higher crustal and upper mantle densities than those of SCS and the Luzon Arc. In addition,there is a large bathymetric difference between the Huatung Basin and the northeastern part of SCS basin. These observations argue against early hypothesis that the Huatung Basin and the northeastern part of SCS basin may once have belonged to one single oceanic crust,in part or in whole. The Gagua Ridge,as a sliver of uplifted oceanic crust,may be r

关键词： precollisional tectonics Taiwan orogen Luzon Arc gravity and magnetic modeling Bouguer gravity anomaly Huatung Basin

Inversion of teleseismic waves at Shidao Seismographic Station

在线全文

学校读者我要写书评

暂无评论

Acta Oceanologica Sinica 2006年第5期25卷 63-73页

作者： RUAN Aiguo li jiabiao HAO Tianyao WU Qingju XU Yi Key Laboratory of Submarine C eosciences of State Oceanic Administration Hangzhou 310012 China Second Institute of Oceanography State Oceanic Administration Hangzhou 310012 China Institute of Geology and Geophysics Chinese Academy of Sciences Beijing 100101 China Institute of Geophysics China Seismological Bureau Beijing 100081 China

Teleseismic datasets at the Shidao Seismographic Station, located in the northwestern South China Sea, are used to determine the earth anisotropy and the vertical distribution pattern of the shear wave velocity by inversion approaches. The rotated correction function is applied to analyzing high quality SeS records from five earthquakes at distance of 25°-35° to obtain shear wave splitting parameters of the lithosphere. The result from the deepest earthquake among the five events indicates that the polarization of the fast shear wave is N94°E, which means the direction of extensional stress or the moving of the upper mantle mass in Xisha Islands is nearly west to east and confirms that the crust in this region is a transitional one and the driving force beneath the crust is from the moving mass consistent with the Eurasian plate. The anisotropy effective thickness is estimated about 100 km based on the time delay of 1.3 s between the fast and slow shear waves. The receiver function is applied to analyzing high quality P wave records from nine earthquakes at distance of 20°- 60° to obtain the vertical distribution pattern of shear wave velocity beneath the station. The result indicates that the crust could be divided into three layers： the uppermost crust （5 km above） is a velocity gradient zone consisting of several small layers, where the shear wave velocity increases from 1.5 to 3.5 km/s gradually; the 5 - 16 km depth interval also consiss of several small layers of which the mean velocity is about 3.8 km/s; and the lower crust （ 16.0 - 26. 5 km） is an obvious low velocity layer with a velocity of about 3.6 km/s. The buried depth of the Moho discontinuity is 26.5 kin, the mean velocity of the layers beneath the Moho is about 4.7 km/s and there is an obvious low velocity layer just beneath the Moho. Moreover, analysis of the arrival time of converted waves and the swinging variation of velocity around the initial model suggests that smaller layers in the model mayb

关键词： South China Sea S wave splitting receiver function S wave velocity structure waveform inversion

Cenozoic Propagated Rifting in the Dangerous Grounds in Response to the Episodic Seafloor Spreading of the South China Sea

在线全文

学校读者我要写书评

暂无评论

Journal of Earth Science 2022年第4期33卷 1031-1046页

作者： Yuanyuan Wang Yanghui Zhao Weiwei Ding Penggao Fang jiabiao li Collaborative Innovation Center of South China Sea Studies Nanjing UniversityNanjing 210093China Key Laboratory of Submarine Geosciences Second Institute of OceanographyMinistry of Natural ResourcesHangzhou 310012China Hubei Key Laboratory of Marine Geological Resources China University of GeosciencesWuhan 430074China

The southern continental margin of the South China Sea has documented multiphase continental rifting corresponding to the propagation of seafloor *** we investigate three multi-channel seismic reflection profiles across different segments of the Dangerous Grounds with a NE-SW *** correlation reveals that the Cenozoic tectono-stratigraphic framework in the Dangerous Grounds is featured with diachronous rifting,which records the successive spreading of East Subbasin and Southwest Subbasin,South China *** reconstructing the tectono-sedimentary evolution history in different segments,we combine the quantification of the brittle extension,tectonic subsidence,as well as the crustal *** provide evidence that the extensional stress migrated from northeast to southwest with the progressive propagation of the seafloor spreading in the oceanic ***,the impact of the tectonic propagation persists even after the cessation of seafloor spreading,evidenced by a longer stretching duration in the West-Dangerous Grounds than that in the eastern ***,a temporary syn-rift subsidence delay synchronously to the spreading of the adjacent oceanic basin is observed along the southern *** observation proves the secondary mantle convection during the seafloor spreading in the southern continental margin,which is related to the propagating rift.

关键词： Dangerous Grounds South China Sea propagated rifting tectonic tectonic subsidence

Methods and procedures to determine the outer limits of the continental shelf beyond 200 nautical miles

在线全文

学校读者我要写书评

暂无评论

Acta Oceanologica Sinica 2013年第12期32卷 126-132页

作者： WU Ziyin li jiabiao JIN Xianglong FANG Yinxia SHANG Jihong li Shoujun Key Laboratory of Submarine Geosciences State Oceanic Administration The Second Institute of Oceanography State Oceanic Administration

This paper establishes techniques and methods to determine a variety of boundaries associated with 200 nautical miles beyond the continental shelf. The methods, based on topography, slope and second-deriv- ative profile integrated analysis, are now able to identify automatically the foot of the continental slope （FOS）. By analyzing the sedimentary profile, the points of 1% sediment thickness are recognized. Through the intersection, cut, deletion and mergence calculation of the extrapolated data set of fLxed-point series, the method succeeds in generating automatically the extrapolated boundaries, including the FOS＋60 M line, the 350 M line, and the 2500 m＋100 M line. In addition, based on the automatic analysis of the topographic profile, it can be applied to determine rapidly the points of maximum water depth. Taking the northern Okinawa Trough （OT） as an example, these methods are used to calculate and examine the boundaries in- cluded in the Submission by the People＇s Republic of China Concerning the Outer limits of the Continental Shelf beyond 200 Nautical miles in Part of the East China Sea （ECS）; the boundaries thus derived have a solid scientific and rational basis.

关键词： 200 nautical miles continental shelf demarcation methodology Okinawa Trough

The formation and tectonic evolution of Philippine Sea Plate and KPR

在线全文

学校读者我要写书评

暂无评论

Acta Oceanologica Sinica 2011年第4期30卷 75-88页

作者： FANG Yinxia li jiabiao li Mingbi DING Weiwei ZHANG Jie The Second Institute of Oceanography State Oceanic Administration Hangzhou 310012 China

The Philippine Sea Plate has an extremely special tectonic background. As an oceanic plate,it is almost entirely surrounded by subduction zones with complex internal tectonic features. On the basis of enormous published literature,this paper offers a comprehensive overview of the tectonic and evolution history of the Philippine Basin and the Kyushu-Palau Ridge（KPR） in the Philippine Sea Plate,and discusses the geological features of KPR. Referring to relevant definitions of various ＂ridges＂ stipulated in United Nations Convention on the Law of the Sea,so the KPR is believed to be a remnant arc formed during the opening of the Parece Vela and Shikoku Basins in the Philippine Sea Plate. It is a submarine ridge on oceanic plate rather than a submarine elevation. And thus,it is not a natural component of the Japan continental margin.

关键词： Philippine Sea Plate West Philippine Basin KPR submarine ridge