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Gao J.,CAS Qingdao Institute of Oceanology | Gao J.,University of Chinese Academy of Sciences | Wu S.,Chinese Academy of Sciences | McIntosh K.,University of Texas at Austin | And 6 more authors.
Tectonophysics | Year: 2015

The northern margin of the South China Sea (SCS) has particular structural and stratigraphic characteristics that are somewhat different from those described in typical passive margin models. The differences are attributable to poly-phase tectonic movements and magmatic activity resulting from the interaction among the Eurasian, Philippine Sea and Indo-Australian plates. Based on several crustal-scale multi-channel seismic reflection profiles and satellite gravity data across the northern SCS margin, this paper analyzes the structures, volcanoes and deep crust of the continent-ocean transition zone (COT) at the mid-northern margin of the SCS to study the patterns and model of extension there.The results indicate that the COT is limited landward by basin-bounding faults near Baiyun sag and is bounded by seaward-dipping normal faults near the oceanic basin in our seismic lines. The shallow anatomy of the COT is characterized by rift depression, structural highs with igneous rock and/or a volcanic zone or a zone of tilted fault blocks at the distal edge. Gravity modeling revealed that a high velocity layer (HVL) with a 0.8-6-km thickness is frequently present in the slope below the lower crust. Our study shows that the HVL is only located in the eastern portion of the northern SCS margin based on the available geophysical data. We infer from this that the presence of an HVL is not required in the COT at the northern SCS margin. The magmatic intrusions and HVL may be related to partial melting caused by the decompression of a passive, upwelling asthenosphere, which resulted primarily in post-rifting underplating and magmatic emplacement or modification of the crust. Based on this study, we propose that an intermediate mode of rifting was active in the mid-northern margin of the SCS with characteristics that are closer to those of the magma-poor margins than those of volcanic margins. © 2015 Elsevier B.V.

Jin-Wang H.,South China University of Technology | Guang-Ming L.,Dongguan University of Technology | Yan S.,Guangzhou Marine Geological Survey Bureau | Zhong-Liang W.,Guangzhou Marine Geological Survey Bureau | Jiu-Chao F.,South China University of Technology
2013 10th International Computer Conference on Wavelet Active Media Technology and Information Processing, ICCWAMTIP 2013 | Year: 2013

Key management is very important for Wireless Sensor Networks' (WSNs) security. Many key management protocols have been proposed recently. However, most of them assume that the area which nodes monitored is equal security, and the probability of nodes being compromised to be the same for every node. In some application environments(e.g. in battle field), the probability of nodes being compromised in an enemy controlled area is larger than in our controlled area. In this paper, a key management method for such application environment which the security is non-uniform is proposed. The optimization for the tradeoff between storage and calculation overhead for Blom Matrix is taken into account; the secret symmetric matrix is generated by conjugate chaotic sequence, it is easy to implemented in physical circuit and more secure. © 2013 IEEE.

Xie X.-N.,Wuhan University | Zhang C.,Wuhan University | Ren J.-Y.,Wuhan University | Yao B.-C.,Guangzhou Marine Geological Survey Bureau | And 3 more authors.
Chinese Journal of Geophysics (Acta Geophysica Sinica) | Year: 2011

Three distinct continental marginal basin types are developed in the South China Sea, i. e. divergence, transform-extensional and flexural-extensional complex types based on the boundary conditions. Difference in tectonic evolution in those basins results in great distinct in sedimentary fill and associated accumulating conditions of hydrocarbon. Source rocks of lacustrine and marine mudstones are mainly developed in northern diverging continental marginal basins in northern South China Sea. Although there developed good continental lacustrine sources, limited hydrocarbon accumulation occur in the adjacent areas around these separated depressions with a relative small scope distribution. In the southern flexural-extensional complex continental marginal basins of the South China Sea, the Zengmu basin underwent the peripheral foreland tectonic stage earlier than other basins such as the Lile, Beikang and Nanweixi basins. An available hydrocarbon accumulating condition occur in those basins, where there are not only large areas and thicknesses of depressions with the sources of coal-bearing and marine mudstones, but also formation of a broad carbonate and reef reservoirs resulted from slow subsidence rates during terminating period of the South China Sea spreading (about 15. 5 Ma). The transform-extensional type of basins in western continental margins of the South China Sea are characterized by natural gases accumulation due to very thick sediments and high heat flow values. Considering of all kinds of geological conditions mentioned above, we believe that the hydrocarbon-bearing perspectives in southern continental marginal basins are superior to these northern continental marginal basins.

Xu S.,China University of Petroleum - Beijing | Wang Y.M.,China University of Petroleum - Beijing | Peng X.C.,Guangzhou Marine Geological Survey Bureau | Zou H.Y.,China University of Petroleum - Beijing | And 3 more authors.
Science China Earth Sciences | Year: 2014

The continental slope of the Taiwan Shoal, which has cultivated numerous submarine canyons, is located in a passive continental margin environment. However, the trend of the Taiwan Canyon, with its 45° intersection angle, is obviously different from that of the erosion valley downward along the continental slope. A distinct break is present in the lower segment of the Taiwan Canyon, which then extends from west to east parallel to the continental slope until finally joining the Manila Trench. By utilizing multiple-beam water depth data, high-resolution seismic data, and sediment cores, this study describes the topographic characteristics of the Taiwan Canyon and provides a preliminary discussion on the origin of the Taiwan Canyon and its effect on deepwater sediment. The terrain, landform, and sediment of the Taiwan Canyon exhibit segmentation characteristics. The upper segment is characterized primarily by erosion, downward cutting with a V shape, and wide development of sliding, slumping, and other gravity flow types. The middle segment is characterized mostly by U-shaped erosion-sedimentation transition and development of an inner levee. The lower segment is characterized primarily by sedimentation and development of a sediment wave. The bottom current has a significant reworking effect on the interior sediments of the canyon and forms reworked sands. The formation and evolution of the Taiwan Canyon is closely related to sediment supply, gravity sliding (slumping), faulting activities, and submarine impaling. Given the sufficient terrigenous clastic supply, the sediments along the continental shelf edge continuously proceed seaward; gliding and slumping in the front edge provide driving forces for the formation of the canyon. Faulting activities result in stratum crushing, and the gravity flow takes priority in eroding the relatively fragile stratum. Thus, the direction of the extension of the canyon crosses the surrounding erosion valley obliquely. Seamounts are formed through submarine impaling. Owing to seamount blocking, the lower segment of the canyon is turned toward the east-west direction. Large amounts of sediments overflow at the turning, forming sediment waves. © 2014, Science China Press and Springer-Verlag Berlin Heidelberg.

Ma D.,Chang'an University | Zhao H.,Chang'an University | Wu Z.,Guangzhou Marine Geological Survey Bureau
Shiyou Diqiu Wuli Kantan/Oil Geophysical Prospecting | Year: 2013

When the traditional three-point positioning method is used to calculate ocean bottom seismograph (OBS) based on the travel-time of direct wave, it is often found that calculated OBS positions are not unique, and sometimes they have great errors. To solve this problem, a mixed positioning method based on the travel-time of direct wave is proposed in this paper. Jointly using the three-point locating method, the least square method and searching method, the non-unique problem caused by direct wave travel-time errors, shotpoint errors of and sound wave velocity errors is solved. The optimal OBS position and the optimal sound wave velocity are found. Application results show this method is an efficient and simple way for improving OBS positioning precision.

Lv S.,South China University of Technology | Wang Z.,South China University of Technology | Sheng Y.,Guangzhou Marine Geological Survey Bureau | Feng J.,South China University of Technology
2012 International Conference on Systems and Informatics, ICSAI 2012 | Year: 2012

Based on fractional Fourier transform and optical Fresnel diffraction, this paper proposes a new image transforming method called fractional Fresnel transform (FFNT). The transformed image can be restored without distortion, and the modification of the transform-domain coefficients can satisfy asymmetry. Using FFNT and Arnold scrambling technique, we conduct some experiments to test the validity of this new transform method. Experimental results show that the new watermarking scheme can achieve excellent performance to JPEG compression and Gaussian low-pass filtering attacks. © 2012 IEEE.

Lu S.-X.,South China University of Technology | Wang Z.-S.,South China University of Technology | Sheng Y.,Guangzhou Marine Geological Survey Bureau | Feng J.-C.,South China University of Technology
Guangzi Xuebao/Acta Photonica Sinica | Year: 2012

A novel image transforming method called Reconstruction Transform is proposed, which can make the double random phase encryption image become non-negative integer value. Reconstruction transform includes two stages, pre-processing and spectral shifting. It's major characteristic is that, compress the interger image to become complex image of half-sized before applying spectral transform to the original image, thus reducing the calculation space in the following steps. The proposed method has the advantage of joint image compression and encryption. Compared with the chaotic image encryption scheme, the cipher-text image of the proposed scheme has lower information entropy. Experimental results show that this method has high security, the decrypted image of this method has little distortion and the cipher-text image has a certain degree of robustness to additive noise attack.

Luo W.-D.,Guangzhou Marine Geological Survey Bureau
Zhongnan Daxue Xuebao (Ziran Kexue Ban)/Journal of Central South University (Science and Technology) | Year: 2011

Concerning about problems appearing in the procedure of the data acquisition and post-processing of the multibeam bathymetric measurement. The security safeguard of equipment, the place and key points of parameter testing, on-site quality control of data acquisition were discussed, the processing points and corresponding measures were described. The method completed the work flow of the multibeam bathymetric measurement, improved the level of the on-site quality control and the quality of data acquisition, make the ocean survey better and promote the development of the multibeam bathymetric measurement.

Zhu B.-D.,Guangzhou Marine Geological Survey Bureau | Liang D.-H.,Guangzhou Marine Geological Survey Bureau | Cui Z.-G.,Guangzhou Marine Geological Survey Bureau
Zhongnan Daxue Xuebao (Ziran Kexue Ban)/Journal of Central South University (Science and Technology) | Year: 2011

The age of the mid and western Pacific seamounts changes between 60 Ma and 150 Ma. These seamounts were formed by magma activities since Cretaceous, and their substrate rocks are Cretaceous basalts. The study results indicate that these seamounts can be divided into top flat seamounts and spire seamounts according to their shape and tectonic features. Magellan seamounts chain locates in western Pacific and is composed of top flat seamounts. Magellan seamounts lay in 1500 m to 6000 m depth, usually composing of a main large seamount and an associated small seamount. The top flat seamount is characterized by large flat roof and steep slope with the listric shape. The flat roofs are covered by Quaternary foraminifer sand and calcium ooze. Most of the seamounts belong to intraplate volcanic seamounts resulted from multiple submarine and plate movements. Complicated submarine morphology and tectonic landform originate from multi-phase large scale volcanic activities. The seamounts drifted with the Pacific Plate extension after the formation of the substrate, then the seamount chains and groups were affected by the activities of active fracture zone hot spots. The seamounts drifted horizontally accompanied by vertical uplift and drop. Some seamounts came out of the sea level as islands with the top eroded, some uplifted near the sea level covered by neritic sediments, and then subsided to the sea bottom of more than 1000 m depth and constructed large scale seamount groups.

Yang Y.,Guangzhou Marine Geological Survey Bureau | Yao H.-Q.,Guangzhou Marine Geological Survey Bureau | Deng X.-G.,Guangzhou Marine Geological Survey Bureau
Zhongnan Daxue Xuebao (Ziran Kexue Ban)/Journal of Central South University (Science and Technology) | Year: 2011

Following the discovery of polymetallic nodules and cobalt-rich crust, seafloor hydrothermal polymetallic sulfide has become another important discovery of seafloor resource exploration. Gravity and magnetic investigation play a significant role in hydrothermal polymetallic sulfide exploration, therefore, the application of gravity and magnetic methods in hydrothermal sulfide exploration was summarized in three aspects: survey means, data processing and gravity and magnetic anomalies characters of seafloor polymetallic sulfide deposit. According to previous studies, some suggestions are obtained and followed as below: (1) Deep-towed survey has widely been used in magnetic survey, but rarely in gravity survey, which is mainly by seafloor site survey. However, it is inferred that deep-towed gravity survey will be widely used in the future. (2) The magnetization inversion and gravity correction of sea-water and sediment layer is crucial to the data processing. (3) Low circular magnetization and high local residual gravity are two important characteristics of seafloor hydrothermal polymetallic sulfide area. (4) Magnetic is better than gravity in hydrothermal sulfide exploration. Therefore, gravity and magnetic methods can play an important role in hydrothermal sulfide exploration, especially magnetic method, which is useful in active and non-active area.

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