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Upper mantle anisotropy of the eastern Himalayan syntaxis and surrounding regions from shear wave splitting analysis

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Science China Earth Sciences 2015年第5期58卷 1872-1882页

作者： CHANG LiJun WANG ChunYong DING ZhiFeng YOU HuiChuan LOU Hai SHAO CuiRu key laboratory of seismic observation and geophysical imaging Institute of GeophysicsChina Earthquake Administration

Polarization analysis of teleseismic data has been used to determine the XKS(SKS,SKKS,and PKS)fast polarization directions and delay times between fast and slow shear waves for 59 seismic stations of both temporary and permanent broadband seismograph networks deployed in the eastern Himalayan syntaxis(EHS)and surrounding *** analysis employed both the grid searching method of the minimum tangential energy and stacking analysis methods to develop an image of upper mantle anisotropy in the EHS and surrounding regions using the newly obtained shear wave splitting parameters and previously published *** fast polarization directions are oriented along a NE-SW azimuth in the ***,within the surrounding regions,the fast directions show a clockwise rotation pattern around the EHS from NE-SW,to E-W,to NW-SE,and then to *** the EHS and surrounding regions,the fast directions of seismic anisotropy determined using shear wave splitting analysis correlate with surficial geological features including major sutures and faults and with the surface deformation fields derived from global positioning system(GPS)*** coincidence between structural features in the crust,surface deformation fields and mantle anisotropy suggests that the deformation in the crust and lithospheric mantle is mechanically *** the EHS,the coherence between the fast directions and the NE direction of the subduction of the Indian Plate beneath the Tibetan Plateau suggests that the lithospheric deformation is caused mainly by *** the regions surrounding the EHS,we speculate that a westward retreat of the Burma slab could contribute to the curved anisotropy *** Tibetan Plateau is acted upon by a NE-trending force due to the subduction of the Indian Plate,and also affected by a westward drag force due to the westward retreat produced by the eastward subduction of the Burma *** two forces contribute to a curved lithospheric deformation that results in the a

关键词： eastern Himalayan syntaxis shear wave splitting anisotropy lithospheric deformation

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基于信道短化和圆球译码的水声通信迭代序列检测

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哈尔滨工程大学学报（英文版） 2024年第1期23卷 238-246页

作者：瞿逢重方浩涂星滨魏艳章旻昊杨劭坚 The Engineering Research Center of Oceanic Sensing Technology and Equipment Ministry of EducationZhoushan 316021China The key laboratory of Ocean observation-imaging Testbed of Zhejiang Province Zhejiang UniversityZhoushan 316021China Hainan Institute of Zhejiang University Sanya 572025China

The demand for high-data-rate underwater acoustic communications(UACs)in marine development is increasing;however,severe multipaths make demodulation a *** decision feedback equalizer(DFE)is one of the most popular equalizers in UAC;however,it is not the optimal *** maximum likelihood sequence estimation(MLSE)is the optimal algorithm,its complexity increases exponentially with the number of channel taps,making it challenging to apply to ***,this paper proposes a complexity-reduced MLSE to improve the bit error rate(BER)performance in multipath *** the proposed algorithm,the original channel is first shortened using a channel-shortening method,and several dominant channel taps are selected for ***,sphere decoding(SD)is performed in the following *** are applied to eliminate inter-symbol interference caused by weak channel *** simulation and sea experiment demonstrate the superiority of the proposed *** simulation results show that channel shortening combined with SD can drastically reduce computational complexity,and iterative SD performs better than DFE based on recursive least squares(RLS-DFE),DFE based on improved proportionate normalized least mean squares(IPNLMS-DFE),and channel estimation-based DFE(CE-DFE).Moreover,the sea experimental results at Zhairuoshan Island in Zhoushan show that the proposed receiver scheme has improved BER performance over RLSDFE,IPNLMS-DFE,and *** with the RLS-DFE,the BER,after five iterations,is reduced from 0.0076 to 0.0037 in the 8–12 k Hz band and from 0.1516 to 0.1145 in the 13–17 k Hz band at a distance of 2000 ***,the proposed algorithm makes it possible to apply MLSE in UAC in practical scenarios.

关键词： Underwater acoustic communications(UACs) Maximum likelihood sequence estimation(MLSE) Channel shortening Sphere decoding(SD) Iterative detection

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Preface to the Special Issue on Advances in seismic Exploration and Monitoring with Active Sources in China

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Earthquake Research in China 2016年第3期30卷 281-283页

作者： Chen Yong Wang Baoshan key laboratory of seismic observation and geophysical imaging Institute of GeophysicsCEA

Analyzing the information carriede by seismic waves is a major means for human beings to have an insight into the structure of the earth’s interior,and by using artificial seismic sources to excite seismic waves,we can obtain high-resolution images for the crustal and smaller scale *** seismic exploration methods have been widely applied to fields such as

关键词： Preface to the Special Issue on Advances in seismic Exploration and Monitoring with Active Sources in China high

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Present status and prospective on the seismic hazard studies of major seismic gaps in the Sichuan-Yunnan region

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Science China Earth Sciences 2024年第11期67卷 3339-3366页

作者： Yong ZHENG Rumeng GUO Dechuan LIU State key laboratory of Geological Processes and Mineral Resources School of Geophysics and Geomatics China University of Geosciences Hubei Subsurface Multi-scale imaging key laboratory National Precise Gravity Measurement Facility Huazhong University of Science and Technology Innovation Academy for Precision Measurement Science and Technology Chinese Academy of Sciences Luojia laboratory

Several seismic gaps have been identified along the Xianshuihe-Xiaojiang fault zone and the Longmenshan fault zone in the Sichuan-Yunnan region, including the Daofu-Shimian gap on the Xianshuihe Fault, the Anninghe-Zemuhe gap, parts of the Xiaojiang Fault, and the Dayi gap between the Wenchuan and Lushan earthquakes. The seismic hazards of the Daofu-Shimian and Dayi gaps have aroused great concern and caused considerable debate. This paper reviews the recent geophysical observations and multidisciplinary studies conducted by domestic and international researchers in these areas, focusing on seismogenic structures, seismic activity, fault locking, stress fields, as well as earthquake triggering, and further analyzes the current controversial viewpoints about the seismic hazards in these regions. Based on the comprehensive analysis, we argue that the kinematic status along the Daofu-Shimian segment may vary significantly along the fault strike. Due to limitations in data and models, there is no consensus on the seismogenic potential of this area. Conversely, the Dayi seismic gap presents a high seismic potential. Furthermore, we delve into the scientific problems associated with major seismic gaps in the Sichuan-Yunnan region and make prospects for the strategy of future work. We propose a research framework that combines dense array and distributed acoustic sensing, artificial intelligence and big data technologies, joint inversion of multiple geophysical fields, as well as numerical simulation techniques for comprehensive seismic hazard analysis in seismic gaps.

关键词： Sichuan-yunnan region seismic gap seismic hazard Present status Prospective

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S-wave velocity structure in the SE Tibetan plateau

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Earthquake Science 2016年第3期29卷 165-172页

作者： Yan Cai Jianping Wu Weilai Wang Lihua Fang Liping Fan Institute of Geophysics China Earthquake Administration key laboratory of seismic observation and geophysical imaging Institute of Geophysics China Earthquake Administration

We use observations recorded by 23 permanent and 99 temporary stations in the SE Tibetan plateau to obtain the S-wave velocity structure along two profiles by applying joint inversion with receiver functions and surface waves. The two profiles cross West Yunnan block （WYB）, the Central Yunnan sub-block （CYB）, South China block （SCB）, and Nanpanjiang basin （NPB）. The profile at -25°N shows that the Moho interface in the CYB is deeper than those in the WYB and the NPB, and the topography and Moho depth have clear correspondence. Beneath the Xiaojiang fault zone （XJF）, there exists a crustal low-velocity zone （LYZ）, crossing the XJF and expanding eastward into the SCB. The NPB is shown to be of relatively high velocity. We speculate that the eastward extrusion of the Tibetan plateau may pass through the XJF and affect its eastern region, and is resisted by the rigid NPB, which has high velocity. This may be the main cause of the crustal thickening and uplift of the topography. In the Tengchong volcanic area, the crust is shown to have alternate high- and low-velocity layers, and the upper mantle is shown to be of low velocity. We consider that the magma which exists in the crust is from the upper mantle and that the complex crustal velocity structure is related to magmatic differentiation. Between the Tengchong volcanic area and the XJF, the crustal velocity is relatively high. Combining these observations with other geophysical evi- dence, it is indicated that rock strength is high and defor- mation is weak in this area, which is why the level of seismicity is quite low. The profile at ~ 23~N shows that the variation of the Moho depth is small from the eastern rigid block to the western active block with a wide range of LVZs. We consider that deformation to the south of the SE Tibetan Plateau is weak.

关键词： SE Tibetan plateau Velocity structure Receiver function Joint inversion Tengchong volcano

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Characterization and analysis of coded excitation ultrasound parameters for rock properties

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Chinese Journal of Acoustics 2017年第1期36卷 29-42页

作者： ZHU Wei WU Hezhen key laboratory of seismic observation and geophysical imaging Institute of GeophysicsCEA Beijing 100081

Coded excitation technology （CET） can effectively enhance the penetration and resolution of ultrasonic testing. To analyze the influence of rock properties on pulse compression performance （PCP） of coded excitation signals （CES）, a numerical simulation, and an ultrasonic experiment on different rock samples are performed; and the detection ability of several CESs are also investigated and compared. The results of experiments showed that the loss of the signal-to-noise ratio （SNR） of Barker coded signal with tapered linear frequency modulated carrier （BTLFM） is always less than Barker coded signal with sine carrier （BS）, while the resolution loss of BTLFM is lower than tapered linear frequency modulated signal （TLFM）. In sum, the results not only verifiy the effectiveness of CET, but also provide a basis for the parameter settings of coded signals used in rock ultrasonic testing.

关键词： rock Characterization and analysis of coded excitation ultrasound parameters for rock properties

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Crustal and uppermost mantle structure of SE Tibetan plateau from Rayleigh-wave group-velocity measurements

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Earthquake Science 2014年第4期27卷 411-419页

作者： Yonghua Li Jiatie Pan Qingju Wu Zhifeng Ding key laboratory of seismic observation and geophysical imaging China Earthquake Administration Institute of Geophysics China Earthquake Administration

A shear-wave velocity model of the crust and uppermost mantle beneath the SE Tibetan plateau was derived by inverting Rayleigh-wave group-velocity mea- surements of periods between 10 and 70 s. Rayleigh-wave group-velocity dispersions along more than 3,000 inter- station paths were measured based on analysis of telese- ismic wavelbrm data recorded by temporary seismic stations. These observations were then utilized to construct 2D group-velocity maps in the period range of 10-70 s. Tile new group-velocity maps have an enhanced resolution compared with previous global and regional group-velocity models in this region because of the denser and more uniform data coverage. The lateral resolution across the region is about 0.5° for the periods used in this study. Local dispersion curves were then inverted for a 3D shear-wave velocity model of the region by applying a linear inversion scheme. Our 3D shear-wave model confirms the presence of low-velocity zones （LVZs） in the crust beneath the northern part of this region. Our irnaging shows that the upper-middle crustal LVZ beneath the Tengchong region is isolated from these LVZs beneath the eastern and northern part of this region. The upper-middle crustal LVZ may be regarded as evidence of a rnagma chamber in the crust beneath the Tengchong Volcanoes. Our model also reveals a slow lithospheric structure beneath Tengchong and a fast shield-like mantle beneath the stable Yangtze block.

关键词： SE Tibetan plateau Shear-wave velocity Rayleigh-wave tomography Group velocity

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Seismological challenges in earthquake hazard reductions:reflections on the 2008 Wenchuan earthquake

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Science Bulletin 2018年第17期63卷 1159-1166页

作者： Yong Chen Jiupeng Hu Fei Peng School of Earth Sciences and Engineering Nanjing University Institute of Geophysics China Earthquake Administration Seismic Observation and Geophysical Imaging Laboratory Institute of Earthquake Forecasting China Earthquake Administration

The Wenchuan earthquake is a natural disaster. Its occurrence and aftermath have demonstrated the critical roles of seismology and earthquake engineering in reducing seismic hazards and damages. However,their existing limitations should also be underscored. This article summarized and reviewed the current scientific understanding of earthquake ruptures, and new insights gained since the Wenchuan event. This study focused on the related challenges to seismology and earthquake engineering as follows:(1) The under-estimation of earthquake risks before occurrences.(2) The current limited data regarding large earthquakes in continental thrust fault systems.(3) The causal relationship between the Wenchuan earthquake and the reservoir impoundment in its vicinity.(4) The identification of low-velocity zone in the crust and its seismogenical role.(5) The casualties and economic losses from a cascade of diverse natural hazards triggered by the ruptures, and the excellent earthquake resistance associated with tunnels in mountainous terrain.

关键词： Wenchuan earthquake Hazard reduction Low-velocity zone Secondary hazard

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Development of a toroidal soft x-ray imaging system and application for investigating three-dimensional plasma on J-TEXT

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Plasma Science and Technology 2024年第3期26卷 94-99页

作者：赵传旭李建超张晓卿王能超丁永华杨州军江中和严伟李杨波毛飞越任正康 the J-TEXT Team International Joint Research laboratory of Magnetic Confinement Fusion and Plasma Physics State Key Laboratory of Advanced Electromagnetic Engineering and TechnologySchool of Electrical and Electronic Engineering and School of PhysicsHuazhong University of Science and TechnologyWuhan 430074People's Republic of China Hubei key laboratory of Optical Information and Pattern Recognition Wuhan Institute of TechnologyWuhan 430205People's Republic of China International Joint Research laboratory of Magnetic Confinement Fusion and Plasma Physics State Key Laboratory of Advanced Electromagnetic Engineering and TechnologySchool of Electrical and Electronic EngineeringHuazhong University of Science and TechnologyWuhan 430074People's Republic of China

A toroidal soft x-ray imaging(T-SXRI)system has been developed to investigate threedimensional(3D)plasma physics on *** T-SXRI system consists of three sets of SXR *** sets are newly developed and located on the vacuum chamber wall at toroidal positionsφof 126.4°and 272.6°,respectively,while one set was established previously atφ=*** set of SXR arrays consists of three arrays viewing the plasma poloidally,and hence can be used separately to obtain SXR images via the tomographic *** sawtooth precursor oscillations are measured by T-SXRI,and the corresponding images of perturbative SXR signals are successfully reconstructed at these three toroidal positions,hence providing measurement of the 3D structure of precursor *** observed 3D structure is consistent with the helical structure of the m/n=1/1 *** experimental observation confirms that the T-SXRI system is able to observe 3D structures in the J-TEXT plasma.

关键词： SXR imaging J-TEXT tokamak three-dimensional measurement MHD

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seismic detections of the 15 February 2013 Chelyabinsk meteor from the dense Chin Array

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Earthquake Science 2016年第4期29卷 221-233页

作者： Lu Li Baoshan Wang Zhigang Peng Weitao Wang key laboratory of seismic observation and geophysical imaging Institute of Geophysics China Earthquake Administration School of Earth and Atmospheric Sciences Georgia Institute of Technology

ChinArray is a dense portable broadband seismic network to cover the entire continental China, and the Phase I is deployed along the north-south seismic belt in southwest China. In this study, we analyze seismic data recorded on the ChinArray following the February 15, 2013 Chelyabinsk （Russia） meteor. This was the largest known object entering the Earth＇s atmosphere since the 1908 Tunguska meteor. The seismic energy radiated from this event was recorded by seismic stations worldwide including the dense ChinAn＇ay that are more than 4000 km away. The weak signal from the meteor event was con- taminated by a magnitude 5.8 Tonga earthquake occur- red ~ 20 min earlier. To test the feasibility of detecting the weak seismic signals from the meteor event, we compute vespagram and perform F-K analysis to the surface-wave data. We identify a seismic phase with back azimuth （BAZ） of 329.7° and slowness of 34.73 s/deg, corre- sponding to the surface wave from the Russian meteor event （BAZ ） 325.97°）. The surface magnitude （Ms） of the meteor event is 3.94 ±0.18. We also perform similar analysis on the data from the broadband array F-net in Japan, and find the BAZ of the surface waves to be 316.61%. With the different BAZs of ChinArray and F-net, we locate the Russian meteor event at 58.80°N, 58.72°E. The relatively large mislocation （-438 km as compared with 55.15°N. 61.41°E by others） may be a result of theweak signals at teleseismic distances.

关键词： ChinArray Russian meteor event F-K analysis

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