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Three dimensional velocity model and its tectonic implications at China Seismic Experimental Site,eastern margin of the Tibetan Plateau

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Science China Earth Sciences 2024年第7期67卷 2268-2290页

作者： Jianping WU Yan CAI Wei WANG Weilai WANG Changzai WANG Lihua FANG Yaning LIU Jing LIU Institute of Geophysics China Earthquake AdministrationBeijing 100081China Beijing Baijiatuan Earth Science National Observation and Research Station Beijing 1095China Beijing Earthquake Agency Beijing 100080China

The China Seismic Experimental Site(CSES)is located at the intersection of the Tibetan Plateau,South China Block,and Indian Plate and has complex geological settings and intense crustal deformation,making it one of the most seismically active areas in Chinese mainland.A high-resolution,three-dimensional(3D)crust-mantle velocity structure is crucial for understanding seismotectonic environments,lithospheric deformation mechanisms,and deep dynamic *** first constructed a high-vertical-resolution 3D initial velocity model using the joint inversion of receiver functions and surface waves and then obtained a 3D P-and S-wave velocity model(CSES-VM1.0)with the highest lateral resolution of 0.25°for the CSES using double-difference *** to the limitations of the Sn observation data,the resolution of the S-wave velocity model in the lower crust and upper mantle was reduced,making it closer to the initial model provided by joint inversion.A comparison with explosive-source seismic data showed that the synthetic P-wave first-arrival travel times of the new model were closer to the observations than those of the previous velocity *** velocity cross-sections across the source areas of the 2022 Lushan MS6.1 and Ludian MS6.8 earthquakes reveal that the former earthquake occurred near a weak contact zone between the Tibetan Plateau and Sichuan Basin,and the rupture of the latter earthquake occurred in a granitic area,with the northern end blocked by rigid high-velocity bodies.A clear high-velocity anomaly zone is distributed along the western margin of the Yangtze Block,revealing the spatial distribution of Neoproterozoic intermediate-basic *** high-velocity zone significantly controls the morphology of fault zones and influences the rupture processes of major *** northeast-southwest and north-south trending high-velocity anomalies were found near Panzhihua,potentially related to Neoproterozoic and Middle-Late Permian intermediate

关键词： Eastern Tibetan Plateau China Seismic Experimental Site Yangtze Block velocity model Double-difference tomography

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Rational Characterization Complex Geology model——Macro velocity model

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Petroleum Science 2004年第1期1卷 23-26,30页

作者： SongWei KeyLabofGeophysicalExplorationunderCNPC UniversityofPetroleumBeijing102249China

The accuracy of migration velocity construction is always a key problem of the image quality of pre-stack depth migration. The velocity model construction process is a process from an unknown to unknown iteration procedure and involves three important steps — model building, migration and model modification. It is necessary to rationally describe the velocity model, according to the complexity of the problem. Taking the Marmousi model as a study object, We established some standards for a rational description of the velocity model on the basis of different velocity space scales, analysis varieties of travel time, and image quality. It is considered that for any given seismic data gathered in the migration velocity model the space wavelength of velocity, which should be expressed in variation of space wavelength of various frequency contents, appears in the seismic data. Some space wavelengths, which are necessary for a description of the model velocity field, are also varying with the layer complexity. For a simple layer velocity structure it is sufficient to apply a simple velocity model (the space wavelength is large enough), whereas, for a complicated layer velocity structure it is necessary to take a velocity model of a more precise scale. In fact, when we establish a velocity model, it is difficult to describe the velocity model at a full space scale, so it is important to limit the space scale of the velocity model according to the complexity of a layer structure and establish a rational macro velocity model.

关键词： velocity model depth migration Marmousi model space wavelength smooth function

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Relocation of Earthquakes in the Northeastern Tianshan Mountains Area and Improvement of Local 1-D Crustal velocity model

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Earthquake Research in China 2012年第3期26卷 321-334页

作者： Sun Anhui Chen Qifu Chen Yong Li Gang Zhang Zhiqiang Institute of Geophysics China Earthquake Administration Beijing 100081 China Institute of Earthquake'Science China Earthquake Administrat'ion Beijing 100036 China China Earthquake Networks Center Beijing 100045 China

We apply three methods to relocate 599 earthquake events that occurred from August 2004 to August 2005 in the northeastern Tianshan Mountains area ( 85°30' ～ 88°30'E,43°00' ～ 44°40' N ) by using travel times recorded by regional seismic network and 10 portable seismic stations deployed around the Urumqi city. By comparing the reliability of different results,we determined a suitable location method,and an improved 1-D crustal velocity model of the study area. The uncertainty of earthquake location is significantly reduced with combined data of seismic network and portable stations. The relocated events are clearly associated with regional tectonics of the northeastern Tianshan Mountains area, and are also in agreement with the existence of active faults imaged by deep seismic reflection profile. The relocated seismicity discovers some potential traces of buried active faults,which need to be validated further.

关键词： Earthquake relocation velocity model The northeastern Tianshan Mountains area Active faults

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A Promising style of growth velocity model of green algae and diatoms in local lake area

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Acta Geochimica 2006年第S1期 162-163页

作者： Zhihong WANG1,2, Fuyi CUI3, Wenxuan CHEN2, Jie JIA2 1 Institution of Environmental Science, South China University of Technology, Guangzhou 510640, China 2 School of Construction, Guangdong University of Technology, Guangzhou 511325, China 3 School of Municipal and Environmental Engineering, Harbin University of Technology, Harbin 150001, China

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Comparison Analysis of Longitudinal Electrical Conductivity Distribution and Seismic Tomography velocity models for the Central Tien Shan Region

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Journal of Earth Science 2023年第2期34卷 580-587页

作者： Olga Zabinyakova Elena Bataleva Irina Medved Research Station of the Russian Academy of Sciences in Bishkek City Bishkek 720049Kyrgyzstan Sobolev Institute of Geology and Mineralogy Siberian Branch of the Russian Academy of SciencesNovosibirsk 630090Russia Trofimuk Institute of Petroleum Geology and Geophysics Siberian Branch of the Russian Academy of SciencesNovosibirsk 630090Russia

The paper is dedicated to consider the approach of longitudinal electrical conductivity maps construction for Central Tien Shan region and to complete the comparison analysis of these maps with related seismic tomography *** results of joint analysis of longitudinal electrical conductivity distribution and seismic tomography velocity models with respect to geological and geophysical senses allow to confirm the already known and to establish the new patterns of structure and geodynamics of the Tien Shan segment of Central Asia such as the manifestation of characteristic structural ensembles,reflection of the longitudinal and transverse segmentation of the Tien Shan,the existence within the framework of a“single”orogen of segments with different near-surface and deep structure and morphological *** well,the correlation between the velocity characteristics and geoelectric properties was *** correlation allows to identify signs of reflection of fault structures in geophysical fields and to clarify the territorial and structural position of both visible and hidden ***,in the paper,the geological interpretation of geophysical anomalies is considered.

关键词： profile magnetotelluric soundings longitudinal electrical conductivity map seismic tomography velocity model Tien Shan geophysics

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A comprehensive factor model of growth velocity of green algae and diatoms in local lake area

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Acta Geochimica 2006年第S1期 163-163页

作者： Zhihong WANG1,2, Fuyi CUI3, Jie JIA2, Wenxuan CHEN2 1 Institution of Environmental Science, South China University of Technology, Guangzhou 510641, China 2 School of Construction, Guangdong University of Technology, Guangzhou 511321, China 3 School of Municipal and Environmental Engineering, Harbin University of Technology, Harbin 150001, China

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Frequency-Domain Multi-Scale Early-Arrival Waveform Tomography with a Time-Domain Wavefield modeling Engine

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Journal of Earth Science 2018年第3期29卷 679-688页

作者： Huachen Yang Juan Wang Taikun Shi Jianzhong Zhang Key Lab of Submarine Geosciences and Prospecting Techniques Ministry of Education College of Marine Geosciences Ocean University of China Evaluation and Detection Technology Laboratory of Marine Mineral Resources Qingdao National Laboratory for Marine Science and Technology

Eariy-arrival waveform tomography （EWT） is one of the most promising techniques for building near-surface velocity model. Based on finite-frequency wave equation, EWT estimates velocities by matching calculated early-arrival waveforms with the observed ones. However, the objective function of EWT can easily converge to local minimum because of the cycle-skipping phenomenon. In order to reduce the cycle-skipping problem, a hybrid-domain early-arrival waveform tomography （HEWT） is proposed in this paper. The forward modeling of HEWT is realized in the time domain where early-arrival waveforms are easier to be selected from seismic data and less memory is needed than they are in the frequency domain. The inversion is implemented in the frequency domain where multi-scale strategy is more convenient to be realized than that in the time domain. Discrete Fourier transformation （DFT） is used to transform the time-domain wavefield to the frequency-domain wavefield. Test results show that HEWT is more competitive than EWT in both accuracy and computational time.

关键词： early-arrival waveform inversion velocity model multi-scale hybrid domain.

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Crustal Structure across the Northwestern Margin of South China Sea:Evidence for Magma-poor Rifting from a Wide-angle Seismic Profile

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Acta Geologica Sinica(English Edition) 2012年第4期86卷 854-866页

作者： DING Weiwei Michael SCHNABEL Dieter FRANKE RUAN Aiguo WU Zhenli The Second Institute of Oceanography State Oceanic Administration Federal Institute for Geoscience and Natural Resource(BGR)

We present results from a 484 km wide-angle seismic profilie acquired in the northwest part of the South China Sea （SCS） during OBS2006 cruise. The line that runs along a previously acquired multi-channel seismic line （SO49-18） crosses the continental slope of the northern margin, the Northwest Subbasin （NWSB） of the South China Sea, the Zhongsha Massif and partly the oceanic basin of the South China Sea. Seismic sections recorded on 13 ocean-bottom seismometers were used to identify refracted phases from the crustal layer and also reflected phases from the crust-mantle boundary （Moho）. Inversion of the traveltimes using a simple start model reveals crustal images in the study area. The velocity model shows that crustal thickness below the continental slope is between 14 and 23 kin. The continental part of the line is characterized by gentle landward mantle uplift and an abrupt oeeanward one. The velocities in the lower crust do not exceed 6.9 km/s. With the new data we can exclude a high-velocity lower crustal body （velocities above 7.0 kin/s） at the location of the line. We conclude that this part of the South China Sea margin developed by a magma-poor rifting. Both, the NWSB and the Southwest Sub-basin （SWSB） reveal velocities typical for oceanic crust with crustal thickness between 5 and 7 kin. The Zhongsha Massif in between is extremely stretched with only 6-10 km continental crust left. Crustal velocity is below 6.5 kin/s; possibly indicating the absence of the lower crust. Multi-channel seismic profile shows that the Yitongansha Uplift in the slope area and the Zhongsha Massif are only mildly deformed. We considered them as rigid continent blocks which acted as rift shoulders of the main rift subsequently resulting in the formation of the Northwest Sub-basin. The extension was mainly accommodated by a ductile lower crustal flows, which might have been extremely attenuated and flow into the oceanic basin during the spreading stage. We compared the crustal stru

关键词： P-wave velocity model magma-poor rifting lower crust flow South China Sea

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The Effect of Strong Near Surface Scattering on Seismic Imaging: Investigation Based on Resolution Analysis

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Communications in Computational Physics 2020年第6期28卷 167-186页

作者： Xiao-Bi Xie Baoqing He Hongxiao Ning Yongqing He Bo Chen Institute of Geophysics and Planetary Physics University of California at Santa CruzCA 95064USA China National Petroleum Corp Bureau of Geophysical Prospecting Inc. Center for Acquisition TechnologyZhuozhouHebeiChina China School of Earth Science and Geological Engineering Sun Yat-Sen UniversityGuangzhouGuangdongChina

In land seismic exploration,strong near-surface heterogeneities can cause serious problems in seismic data acquisition and the quality of depth *** introducing random velocity models to simulate velocity fluctuations in the near-surface layer and using the point spread function to characterize image quality,we examine how the scattering generated in near-surface heterogeneities can affect the subsurface *** addition to the commonly known scattering noises which lower the signal to noise ratio in seismic data,our results also reveal that intermediate scale hetero-geneities generate forward scattering which forms phase or travel time *** to intermediate-scale uncertainty in the shallow part of the migration velocity model,these phase changes are carried to the target by the extrapolated wavefields,breaking the zero phase image condition at the image *** is a primary reason for deteriorated image quality in regions with strong near-surface *** this intermediate-scale information can be obtained and built into the migration velocity,the subsurface image quality can be largely *** results can be the ba-sis for further numerical investigations and field *** proposed analysis method can also be used to evaluate other potential methods for dealing with near-surface scattering.

关键词： Reverse time migration shallow scattering velocity model prestack depth imaging seismic resolution

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Focal mechanism inversion of the 2018 M_(W)7.1 Anchorage earthquake based on high-rate GPS observation

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Geodesy and Geodynamics 2021年第6期12卷 381-391页

作者： Yanhao Zhang Caijun Xu Jin Fang Zelong Guo School of Geodesy and Geomatics Wuhan UniversityWuhan430079China Key Laboratory of Geospace Environment and Geodesy Ministry of EducationWuhan UniversityWuhan430079China Key Laboratory of Geophysical Geodesy Ministry of Natural ResourcesWuhan430079China COMET School of Earth and EnvironmentUniversity of LeedsLeedsLS29JTUK German Research Centre for Geosciences(GFZ) Section of Remote SensingPotsdam14473Germany

The M_(W)7.1 Anchorage earthquake is the most destructive earthquake since the 1964 M_(W)9.2 great Alaska earthquake in the United *** this study,high-rate GPS data and near-field broadband seismograms are used in separate and joint inversions by the generalized Cut-and-Paste(gCAP)method to estimate the focal *** order to investigate the influence of crustal velocity structure on the focal mechanism inversion results,two velocity models(Crustl.0 and Alaska Earthquake Center(AEC))are used for detailed comparison and *** results show that:(1)The two nodal planes of the optimal double-couple solution are nearly north-south striking,with dip angles of about 30°and 60°respectively,and the centroid focal depth is 54-55 km,which is an intraplate normal fault event.(2)The inversion results for the two types of data and the two velocity models are consistent with some previous studies,which indicates that the results are stable and *** more accurate velocity structure model is helpful for focal mechanism inversion of the complex earthquake.(3)The inclusion of high-rate GPS data in joint inversion provides a more effective constraint on centroid depth.

关键词： M_(W)7.1 Anchorage earthquake High-rate GPS and seismogram velocity model Joint inversion Centroid depth

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