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crustal structure of the Jurassic Quiet Zone in the West Pacific Ocean:Insights from 2D Multichannel Seismic Reflection Profiles

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中国海洋大学学报:英文版 2023年第5期22卷 1289-1299页

作者： YANG Xiaodong LIN Jingxue ZHANG Jinchang LUO Yiming ZHANG Xubo QIN Zhen HUANG Yanming CAS Key Laboratory of Ocean and Marginal Sea Geology South China Sea Institute of OceanologyInnovation Academy of South China Sea Ecology and Environmental EngineeringChinese Academy of SciencesGuangzhou 511458China Southern Marine Science and Engineering Guangdong Laboratory(Guangzhou) Guangzhou 511458China China-Pakistan Joint Research Center on Earth Science CAS-HECIslamabad 45320Pakistan University of Chinese Academy of Sciences Beijing 100049China Department of Ocean Science and Engineering Southern University of Science and TechnologyShenzhen 518055China Chongqing Institute of Geological Survey Chongqing 401122China Key Laboratory of Exploration Technologies for Oil and Gas Resources Ministry of EducationYangtze UniversityWuhan 430100China

The Jurassic oceanic crust is the oldest existing oceanic crust on earth,and although distributed sparsely,carries essential information about the earth's evolution.The area around the Pigafetta Basin in the west Pacific Ocean(also known as the Jurassic Quiet Zone,JQZ)is one of a few areas where the Jurassic oceanic crust is present.This study takes full advantage of high-resolution multichannel seismic reflection profiles in combination with bathymetry,magnetic,and gravity data from the JQZ to examine the structure,deformation,and morphology of the Jurassic oceanic crust.Our results show the following insights:1)The Moho lies at 2–3 s in two-way travel time beneath the seafloor with the segmented feature.The gaps between the Moho segments well correspond to the seamounts on the seafloor,suggesting the upward migration of magma from the mantle has interrupted the pre-existing Moho.2)The oceanic crust is predominantly deformed by crustal-scale thrust faults,normal faults cutting through the top of basement,and vertical seismic disturbance zones in association with migration of thermal fluids.The thrust faults are locally found and interpreted as the results of tectonic inversion.3)Seafloor morphology in the JQZ is characterized by fault scarps,fold scarps,seamounts,and small hills,indicating the occurrence of active faults.4)The oceanic crust in the JQZ and East Pacific Rise has many structural and geometrical variations,such as the thickness of sediments,seafloor topography,basement morphology,fault size and type.

关键词： Jurassic oceanic crust crustal structure Moho fault sedimentary deformation

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crustal structure of the Chuan-Dian Block Revealed by Deep Seismic Sounding and its Implications for the Outward Expansion of the East Tibetan Plateau

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Acta Geologica Sinica(English Edition) 2022年第6期96卷 1932-1944页

作者： XIONG Xiaosong WANG Guan LI Qiusheng LU Zhanwu GAO Rui FENG Shaoying WU Guowei SinoProbe Center Chinese Academy of Geological SciencesBeijing 100037China Key Laboratory of Deep-Earth Dynamics of the Ministry of Natural Resources Institute of GeologyChinese Academy of Geological SciencesBeijing 100037China School of Earth Science and Geological Engineering Sun Yat-Sen UniversityGuangzhou 510275China Geophysical Exploration Center Chinese Earthquake AdministrationZhengzhou 450002China

The Chuan-Dian Block(CDB)is located in the southeastern margin of the Tibetan Plateau,with a complex geological structure and active regional faults.The present tectonic condition with strong crustal deformation is closely related to the ongoing collision of the India and Eurasia plates since 65 Ma.The study of the crustal structure of this area is key to revealing the evolution and deep geodynamics of the lateral collision zone of the Tibetan Plateau.Deep seismic sounding is the most efficient method with which to unravel the velocity structure of the whole crust.Since the 1980s,19 deep seismic sounding profiles have been captured within the CDB area.In this study,we systematically integrate the research results of the 19 profiles in this area,then image the 3D crustal velocity,by sampling with a 5 km spacing and 2D/3D Kriging interpolation.The results show the following.(1)The Moho depth in the study area deepens from 30 km in the south to 66 km in the north,whereas there is no apparent variation from west to east.The Pn wave velocity is higher in stable tectonic units,such as 7.95 km/s in the Lanping-Simao block and 7.94 km/s in the western margin of the Yangtze block,than in active or mobile tectonic units,such as 7.81 km/s in the Baoshan block,7.72 km/s in the Tengchong block and 7.82 km/s in the Zhongdian block.(2)The crustal nature of the Tengchong block,the northern Lanping-Simao block and the Zhongdian block reflects a type of orogenic belt,having relatively strong tectonic activities,whereas the crustal nature of the central Lanping-Simao block and the western margin of the Yangtze block represents a type of platform.The different features of the upper-middle crust velocity,Moho depth and Pn wave velocity to both sides of the Red River fault zone and the Xianshuihe fault zone,reflect that they are clearly ultra-crustal.(3)Based on the distribution of the low velocity zones in the crust,the crustal material of the Tibetan Plateau is flowing in a NW–SE direction to the north of 26°N and to the west of 101

关键词： deep seismic sounding crustal structure outward expansion Chuan-Dian Block southeastern margin of the Tibetan Plateau

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Hyperextended crustal structure of the Qiongdongnan Basin and subsequent magmatic influence from the Hainan mantle plume

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Science China Earth Sciences 2022年第5期65卷 845-862页

作者： Shaohong XIA Chaoyan FAN Dawei WANG Jinghe CAO Fang ZHAO Key Laboratory of Ocean and Marginal Sea Geology South China Sea Institute of OceanologyChinese Academy of SciencesGuangzhou 510301China Sanya Institute of Oceanology SCSIOSanya 572100China Institute of Deep-sea Science and Engineering Chinese Academy of SciencesSanya 572000China

The Qiongdongnan Basin(QDNB)is a rift basin located in the extension direction of the oceanic ridge of the Northwest Subbasin of the South China Sea.This basin is surrounded by Late Cenozoic Ocean Island Basalts(OIBs)magmatism associated with the putative Hainan mantle plume.However,how the Hainan mantle plume has affected the QDNB has not been studied in detail.To reveal the crustal structure of the QDNB and the possible influence of the Hainan mantle plume,we conducted a wide-angle seismic exploration from Hainan Island across the QDNB to the Xisha Block,and obtained the crustal structure by travel-time tomography.The results show that the crustal stretching factors of the Northern and Southern Rises of the QDNB are estimated to be 1.3-2.0,indicating slight or moderate crustal thinning.Whereas,the crustal stretching factor in the Central Depression of the QDNB is estimated to be more than 3.0,which means that the crust has been hyperextended.Controlled by two detachment faults(F2 and F11),the upper and lower crust show brittle and ductile thinning,respectively.Three anomalous low-velocity conduits penetrating the crystalline crust are developed in the Songnan Uplift and the Southern Rise of the QDNB.Their P-wave velocities are 5.5-6.0 km s^(−1),which are significantly lower than those of the surrounding crust(6.0-6.8 km s^(−1)).The Late Cenozoic magmatic intrusions(e.g.,sills and dikes)and hydrothermal activities can be observed in the sedimentary strata above these low-velocity conduits.We interpret that the low-velocity conduits might be the crustal magmatic footprints of the Hainan mantle plume,due to the correlated distributions of OIB-type magmatism,the magmatic intrusion patterns,the deep structure of the Hainan mantle plume and the high heat flow of 95 mW m^(−2).Thus,we propose that the crustal structure of the QDNB is the product of crustal hyperextension in the rifting stage and subsequently affected by the Hainan mantle plume magmatism.This study provides a typical case for understanding the influence

关键词： crustal structure Hyperextension Magmatism Hainan mantle plume Qiongdongnan Basin

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crustal structure and Extension from Slope to Deepsea Basin in the Northern South China Sea

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Journal of China University of Geosciences 2009年第1期20卷 27-37页

作者：胡登科周蒂吴湘杰何敏庞雄王玉薇 Key Laboratory of Marginal Sea Geology Chinese Academy of SciencesGuangzhou 510301 China Graduate University of Chinese Academy of Sciences Beijing 100049 China Key Laboratory of Marginal Sea Geology South China Sea Institute of Oceanology Chinese Academy of SciencesGuangzhou 510301 China Institute of CNOOC Ltd ShenzhenGuangzhou 510240 China Guangdong Geological Survey Guangzhou 510080China

The newly acquired long-cable multi-channel seismic （MCS） lines were used to study the crustal structure and extension in an NW-SE elongated 150 km by 260 km strip from the slope to the deepsea basin in the northern South China Sea （SCS）. These profiles are of good penetration that Moho is recognizable in -70% length of the lines. Seismostratigraphic interpretation and time-depth conversion were conducted. A power function D = ath ＋ c was used in the time-depth conversion, which avoided the under- or over-estimation of the depths of deep-seated interfaces by cubic or quadratic polynomial functions. Contour maps of basement depth, Moho depth, crustal thickness, and crustal stretching factor were obtained for the study area. In the dip direction, the Mobo depth decreases stepwisely from 28 km in the outer shelf southwards to 19, 15, and 12 km in the deepsea basin, with ramps at the shelf break, lower slope, and the continent ocean boundary （COB）, respectively. Accordingly, the crustal thickness decreased southwards from 25 to 15, 13, and 7 km, respectively. Under the center of the Baiyun （白云） sag, the crust thins significantly to 〈 7 km. The crustal stretching factor βc was calculated by assuming the original crust thickness of 30 km. In the centers of the Baiyun sag, βc exceeds 5. Tertiary and Quaternary volcanic activities show a general trend of intensifying towards the COB. An important finding of this study is the along-strike variation of the crustal structure. A Moho rise extends from the COB NW-ward until the shelf break, about 170 km long and 50-100 km wide, with Moho depth 〈 20 km. This is called the Baiyun Moho Nose, which is bounded to the east, west, and north by belts of high Moho gradients indicative of crustal or even lithospheric faults. The doming of Moho in the nose area might be the cause of the W-E segmentation of the crustal and geological structures along the slope of the northern South China Sea, and the cause of the strong crustal stretching in the Baiyun and Liwan （荔湾） sags.

关键词： crustal structure Moho stretching Baiyun sag northern South China Sea.

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crustal structure of Yunnan Province of China from Teleseismic Receiver Functions:Implications for Regional Crust Evolution

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Journal of Earth Science 2018年第6期29卷 1419-1430页

作者： Fang Wang Shuangxi Zhang Mengkui Li Department of Geophysics School of Geodesy and GeomaticsWuhan UniversityWuhan 430079China Key Laboratory of Geospace Environment and Geodesy of the Ministry of Education Wuhan UniversityWuhan 430079China Collaborative Innovation Center of Geospace Information Science Wuhan UniversityWuhan 430079China

Yunnan Province is located on the southeastern margin of Tibet and represents an important marker in understanding the tectonic evolution of Tibetan Plateau. In this study, we calculated teleseismic P-wave receiver functions at 49 permanent broadband seismic stations in Yunnan Province and estimated crustal thickness and the bulk crust ratios of P-wave to S-wave velocities using the H-κ method together with more detailed crustal structural profiles from the common conversion point stacking method. There is a significant transition of Moho interface and lower crustal composition along latitude 26°N in northwestern Yunnan. Decrease of crustal thickness with a concomitant increase of Poisson’s ratio occurs at station CUX. An interesting phenomenon is that a step-like Moho fashion is observed at several stations, which might correspond to local thermal activities, such as partial melt/lower crust delamination. Our results show changes in crustal properties appear to be associated with varieties in upper mantle structure and compositions. We propose the controlling factor of the dynamic processes below 26°N is the result of eastern forward subduction of the Indian Plate; the northern part is controlled by the redirected material flow from the SE Tibet.

关键词： crustal structure receiver function Poisson’s ratio tectonic evolution

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crustal structure beneath Yinggehai Basin and Adjacent Hainan Island, and Its Tectonic Implications

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Journal of China University of Geosciences 2009年第1期20卷 13-26页

作者：吴世敏丘学林周蒂曾刚平夏戡原叶三余 Key Laborotary of Marginal Sea Geology South China Sea Institute of Oceanology Chinese Academy of SciencesGuangzhou 510301 China Hainan Branch of State Seismological Bureau Haikou 570203 China NedreToppenhaug 100 N-1353 Brums Verk Norway

Two NE-SW trending wide-angle seismic profiles were surveyed across the Chinese side of the Yinggehai （莺歌海） basin （YGHB） with ocean bottom hydrophones （OBHs） and piggyback recorded by onshore stations located on the Hainan （海南） Island. Detailed velocity-depth models were obtained through traveltime modeling and partially constrained by amplitude calculations. More than 15 km Tertiary sedimentary infill within the YGHB can be divided in to three layers with distinct velocity-depth distribution. Overall, the upper layer has a high velocity gradient with 3.8--4.1 km/s at its bottom, consistent with progressive compaction and diagenesis. Its thickness increases gradually towards the basin center, reaching 4.5 km along the southern profile. The middle layer is characterized in its most part as a pronounced low velocity zone （LVZ） with average velocity as low as 3.0 km/s. Its thickness increases from 3.0 to over 4.5 km from NW towards SE. The primary causes of the velocity inversion are high accumulation rate and subsequent under-compaction of sediments. The velocity at the top of the lower layer is estimated at about 4.5 km/s. Despite strong energy source used （4 × 12L airgun array）, no reflections can be observed from deeper levels within the basin. Towards NE the basin is bounded sharply by a clear and deep basement fault （Fault No. 1）, which seems to cut through the entire crust. A typical continental crust with low-velocity middle crust is found beneath the coast of the western Hainan Island. Its thickness is determined to be 28 km and shows no sign of crustal thinning towards the basin. The sharp change in crustal structure across Fault No. 1 indicates that the fault is a strike-slip fault. The crustal structure obtained in this study clearly favors the hypothesis that the YGHB is a narrow pull-apart basin formed by strike-slip faulting of the Red River fault zone.

关键词： crustal structure strike-slip fault pull-apart basin Yinggehai South China Sea

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crustal structure in northern margin of Tianshan mountains and seismotectonics of the 1906 Manas earthquake

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Acta Seismologica Sinica(English Edition) 2001年第5期14卷 491-502页

作者： WANG Chun-yong Institute of Geophysics China Seismological Bureau Beijing China Institute of Geophysics China Petroleum University Beijing China

The thin-skinned structure in the crust of the northern Tianshan piedmont is explored by an 86-km-long, NS-trending deep seismic reflection profile through the Urumqi depression of the north margin of the Tianshan mountains. On the CDP stacking section, the first- and second-row parallel to anticlines in the north margin of the Tianshan mountains are shown on the segment to the south of the Shihezi. The detachments, corresponding to the reflection events at TWT 2.5-3.0 s and 5.5-6.0 s respectively, join the crustal deep structure to the reverse fault-fold zone. The Manas thrust extends downwards in listric shape, merges into the detachment at about TWT 2.5 s and joins to the Qingshuihe thrust. The reflection events on 5.5-6.0 s are corresponding to the main detachment, which joins the lower Manas anticline, and finally converge to the Jungar Southern Marginal Fault. A 12-14 km-thick sedimentary basin exists on the region in the north to the Shihezi. The depth of the Moho discontinuity beneath the Junggar basin is about 45 km, and increases southwards to 50 km. The crustal structure inferred from the deep seismic sounding profile and the Bouguer anomaly in the same region is consistent with the image from the deep seismic reflection profile. The seismogenic model of the 1906 Manas earthquake is related to the fault system, which consists of the Qingshuihe thrust, the detachments and the shallow Manas ramp.

关键词： crustal structure deep seismic reflection profile reverse fault-fold zone Manas earthquake area P315.2

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crustal structure in Xiaojiang fault zone and its vicinity

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Earthquake Science 2009年第4期22卷 347-356页

作者： Chunyong Wang Hai Lou Xili Wang Jiazheng Qin Runhai Yang Jinming Zhao Institute of Geophysics China Earthquake Administration Beijing 100081 China Earthquake Administration of Yunnan Province Kunming 650224 China

Based on the integrative interpretation of travel-time data and amplitude information obtained from the deep seismic sounding experiment on the Chuxiong-Luoping profile, eastern Yunnan province, carried out in January of 2005, we present a 2-D P wave velocity structure along the profile. The crustal structure shows remarkable contrasts between the two sides of the Xiaojiang fault zone, although the whole profile is situated within the Yangtze platform. The average P wave velocities of the crust on the west and east sides of the fault zone are 6.21 km/s and 6.32 km/s, respectively, and the crustal thicknesses are 41 km and 45 km, respectively. These results imply that the crust to the east of the Xiaojiang fault zone presents characteristics of crustal structure in a stable platform, while the crust to the west is complicated with a lower velocity zone in middle of the upper crust. The average velocity of 6.21 km/s is lower than the global continental crustal average （6.30 km/s）, indicating that the region is tectonically active. According to the lateral variation of velocity and depth of interfaces （including the Moho）, it is inferred that the Xiaojiang fault zone has cut through the whole crust. It is also deduced that existence of low velocity zone in middle of the upper crust is conducive to the south-southeastern sliding of the Sichuan- Yunnan （Chuan-Dian） rhombus block.

关键词： Xiaojiang fault zone crustal structure deep seismic sounding seismicity low velocity zone

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crustal structure of northeastern Tibetan plateau and Ordos block:Waveform interpretation of the Maqen-Jingbian seismic refraction profile

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Earthquake Science 2009年第4期22卷 365-371页

作者： Fuyun Wang Hong Shang Xiankang Zhang Geophysical Exploration Center China Earthquake Administration Zhengzhou 450002 China

The Maqen-Jingbian wide-angle seismic reflection and refraction experiment was carried out in 1998, which aims at determining detailed structure in the crust and top of the upper mantle and understanding structural relation between the northeastern Tibetan plateau and the Ordos block. The 1-D crustal models inferred by waveform inversion show strong variations in crustal structure, which can be classified into four different types： ① an Ordos platform with the Proterozoic crust and two high-velocity layers in the northeast section, ② a transitional crust between the northeastern Tibetan plateau and the Ordos block across the Haiyuan earthquake zone, ③ the Qilian orogenic zone in the central part, and ④ the Qinling orogenic zone in the southwestern section. The Moho depth increases from -42 km to -62 km from the NE part to the SW part of the profile. The crystalline crust consists of the upper crust and lower crust in northeastern Tibetan plateau. There is an obviously low P-wave velocity layer dipping northeastward, which is 12-13 km thick, at the bottom of the upper crust in Qinling orogenic zone and Haiyuan earthquake zone. The lower crust is characterized by alternating high and low P-wave velocity layers. Beneath Ordos block, i.e., the NE part of the profile, the crust shows quite a smooth increase in P-wave ve- locity down to the Moho at a depth of about 42 km.

关键词： crustal structure northeastern Tibetan plateau Ordos block waveform interpretation seismic refraction

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crustal structure of the northeastern Tibetan plateau,the Ordos block and the Sichuan basin from ambient noise tomography

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Earthquake Science 2010年第5期23卷 465-476页

作者： Yong Zheng Yingjie Yang Michael H. Ritzwoller Xiufen Zheng Xiong Xiong Zuning Li Key Laboratory of Dynamic Geodesy Institute of Geodesy and Geophysics Chinese Academy of Sciences Wuhan 430077 China Department of Physics University of Colorado Boulder CO 80303 USA Institute of Geophysics China Earthquake Administration Beijing 100081 China Earthquake Administration of Fujian Province Fuzhou 350003 China

We apply ambient noise tomography to significant seismic data resources in a region including the northeastern Tibetan plateau, the Ordos block and the Sichuan basin. The seismic data come from about 160 stations of the provincial broadband digital seismograph networks of China. Ambient noise cross-correlations are performed on the data recorded between 2007 and 2009 and high quality inter-station Rayleigh phase velocity dispersion curves are obtained between periods of 6 s to 35 s. Resulting Rayleigh wave phase velocity maps possess a lateral resolution between 100 km and 200 kin. The phase velocities at short periods （〈20 s） are lower in the Sichuan basin, the northwest segment of the Ordos block and the Weihe graben, and outline sedimentary deposits. At intermediate and long periods （〉25 s）, strong high velocity anomalies are observed within the Ordos block and the Sichuan basin and low phase velocities are imaged in the northeastern Tibetan plateau, reflecting the variation of crustal thickness from the Tibetan plateau to the neighboring regions in the east. crustal and uppermost mantle shear wave velocities vary strongly between the Tibetan plateau, the Sichuan basin and the Ordos block. The Ordos block and the Sichuan basin are dominated by high shear wave velocities in the crust and uppermost mantle. There is a triangle-shaped low velocity zone located in the northeastern Tibetan plateau, whose width narrows towards the eastern margin of the plateau. No low velocity zone is apparent beneath the Qinling orogen, suggesting that mass may not be able to flow eastward through the boundary between the Ordos block and the Sichuan basin in the crust and uppermost mantle.

关键词： phase velocity Ordos block ambient noise tomography crustal structure

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