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Preliminary Results of the Seismicity Monitoring Experiment around the 2019 Mw5.4 Earthquake Epicenter in the Central South China Sea Basin

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Journal of Earth Science 2024年第1期35卷 212-220页

作者： Wenfei Gong Aiguo Ruan Xiongwei Niu Zhenjie Wang Pingchuan Tan Xiaodong Wei Wei Wang Zhengyi Tong liqun Cheng Fansheng Kong Shaoping Lu Jianke Fan Weiwei Ding Jinyao Gao Chunguo Yang jiabiao li School of Oceanography Shanghai Jiaotong UniversityShanghai 200240China Key Laboratory of submarine Geosciences Second Institute of OceanographyMinistry of Natural ResourcesHangzhou 310012China Zhejiang Earthquake Administration Hangzhou 310013China School of Earth Sciences Zhejiang UniversityHangzhou 310027China Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai) Zhuhai 519082China School of Earth Sciences and Engineering Sun Yat-sen UniversityZhuhai 519082China Institute of Oceanology Chinese Academy of SciencesQingdao 266071China

On September 5,2019,a moderate earthquake of Mw5.4 unexpectedly occurred in the apparently quiescent central basin of the South China Sea.We immediately carried out a seismicity monitoring experiment around the epicenter by using broadband ocean bottom seismometers(OBS)for the following three scientific targets.The first is knowing the earthquake seismogenic mechanism,fault structure and further development.The second is finding the role of the residual spreading ridge playing in earthquake processes and further revealing the deep structures of the ridge directional turning area.The third is confirming the existence and significance of the so called“Zhongnan fault”.This paper reports the preliminary results of the first phase experiment.Five OBSs were deployed for seismicity monitoring with a duration of 288 days,but only three were recovered.Micro-earthquakes were firstly detected by an automatic seismic phase picking algorithm and then were verified by analyzing their seismic phases and time-frequency characteristics in detail.A total of 21,68 and 89 microearthquakes were picked out from the three OBSs respectively within the distance of 30 km.The dominant frequency of these micro-earthquakes is 12-15 Hz,indicating tectonic fracturing.During the first two months after the mainshock the seismicity was relatively stronger,and micro-earthquakes were still occurring occasionally till the end of observation,indicating the epicenter area is active.We used Match&Locate method to locate 57 micro-earthquakes preliminarily.Their spatial distribution shows that the seismicity is developed mainly along the NE direction roughly parallel to the residual ridge with depth variations between 10-20 km.

关键词： South China Sea microseismic monitoring earthquakes fault broadband OBS

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

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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 spreading.Here we investigate three multi-channel seismic reflection profiles across different segments of the Dangerous Grounds with a NE-SW direction.Stratigraphic 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 Sea.By reconstructing the tectono-sedimentary evolution history in different segments,we combine the quantification of the brittle extension,tectonic subsidence,as well as the crustal thinning.Results provide evidence that the extensional stress migrated from northeast to southwest with the progressive propagation of the seafloor spreading in the oceanic basin.Besides,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 area.Moreover,a temporary syn-rift subsidence delay synchronously to the spreading of the adjacent oceanic basin is observed along the southern margin.This 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

Crustal structure and variation along the southern part of the Kyushu-Palau Ridge

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Acta Oceanologica Sinica 2022年第1期41卷 50-57页

作者： Xiaodong Wei Weiwei Ding Aiguo Ruan Jie Zhang Xiongwei Niu jiabiao li Yong Tang Key Laboratory of Submarine Geosciences Ministry of Natural Resources/Second Institute of OceanographyMinistry of Natural ResourcesHangzhou 310012China Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai) Zhuhai 519080China School of Oceanography Shanghai Jiao Tong UniversityShanghai 200240China

As an interoceanic arc,the Kyushu-Palau Ridge(KPR)is an exceptional place to study the subduction process and related magmatism through its interior velocity structure.However,the crustal structure and its nature of the KPR,especially the southern part with limited seismic data,are still in mystery.In order to unveil the crustal structure of the southern part of the KPR,this study uses deep reflection/refraction seismic data recorded by 24 ocean bottom seismometers to reconstruct a detailed P-wave velocity model along the ridge.Results show strong alongridge variations either on the crustal velocity or the thickness of the KPR.P-wave velocity model is featured with(1)a crustal thickness between 6–12 km,with velocity increases from 4.0 km/s to 7.0 km/s from top to bottom;(2)high gradient(~1 s^(-1))in the upper crust but low one(lies in the lower crust beneath seamounts.By comparing with the mature arc in the Izu-Bonin-Mariana arc in the east,this study suggests the southern part of KPR is a thicken oceanic crust rather than a typical arc crust.The origin of low velocities in the lower crust and upper mantle may be related with crustal differentiation,which implies advanced crustal evolution from normal oceanic crust to partly thicken oceanic crust.High velocities in the lower crust are related to the difference in magmatism.

关键词： P-wave velocity structure ocean bottom seismometer Kyushu-Palau Ridge magmatism thicken oceanic crust

Erosion-Dominated Modern Submarine Gully–Canyon–Channel Systems in Offshore Northwest Palawan， Southern South China Sea

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Journal of Earth Science 2023年

作者： Han Shi Weifeng Ding Shaoru Yin Jinyao Gao jiabiao li College of Marine Science and Technology China University of Geosciences Key Laboratory of Submarine Geosciences Second Institute of Oceanography Ministry of Natural Resources

We investigated the morphology and sedimentary state of an extensive modern canyon system on the northwest continental slope of Palawan Island in the southern South China Sea using multibeam bathymetry data and chirp sub-bottom profiles. The canyon system in northwest Palawan consists of a fairly large dendritic canyon， a braided canyon， and a set of short， straight， and slope-confined gullies. The erosion state covers 71% of the system. Sediment accumulates downstream of the bend’s inner side in the proximal main stem of the dendritic canyon and is eroded in its outer side. In the distal main stem， sediment is deposited inside and outside the bend. In most of the system’s tributaries， decreasing slope gradients result in more sediment deposition. There is thick aggradation of sediment waves in the interfluve throughout the system， which exhibit increasing levels of stratification as the slope decreases. The lack of slump scars and headward erosion at the canyon heads， as well as the presence of regular gullies and sediment wave fields， suggest that large areas of unconfined downslope turbidity currents formed the system. We propose that frequent storms in northwestern Palawan triggered these currents by resuspending sediments on the shelf.

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Oceanic crustal structure and tectonic origin of the southern Kyushu-Palau Ridge in the Philippine Sea

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Acta Oceanologica Sinica 2022年第1期41卷 39-49页

作者： Xiongwei Niu Pingchuan Tan Weiwei Ding Wei Wang Yao Wei Xiaodong Wei Aiguo Ruan Jie Zhang Chunyang Wang Yong Tang jiabiao li Key Laboratory of Submarine Geosciences Ministry of Natural Resources/Second Institute of OceanographyMinistry of Natural ResourcesHangzhou 310012China School of Oceanography Shanghai Jiao Tong UniversityShanghai 200240China Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai) Zhuhai 519080China

A new high-resolution velocity model of the southern Kyushu-Palau Ridge(KPR) was derived from an activesource wide-angle seismic reflection/refraction profile. The result shows that the KPR crust can be divided into the upper crust with the P-wave velocity less than 6.1 m/s, and lower crust with P-wave velocity between 6.1 km/s and 7.2 km/s. The crustal thickness of the KPR reaches 12.0 km in the center, which gradually decreases to 5.0–6.0 km at sides. The velocity structure of the KPR is similar to the structures of the adjacent West Philippine Basin and Parece Vela Basin(PVB), indicating a typical oceanic crust. Isostatic analysis shows that some regional compensation occurs during the loading of the KPR, which implies that the KPR was built mainly by magmatism during the splitting of the Izu-Bonin-Mariana arc and the following back-arc seafloor spreading of the PVB during30–28 Ma BP. The absence of the thick middle crust(6.0–6.5 km/s) and high velocity lower-crustal layers(7.2–7.6 km/s) suggest that arc magmatism plays a less important role in the KPR formation.

关键词： P-wave crustal structure ocean bottom seismometer Kyushu-Palau Ridge oceanic crust

Mantle flow underneath the South China Sea revealed by seismic anisotropy

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National Science Review 2023年第10期10卷 54-61页

作者： Fansheng Kong Rui Gao Stephen S.Gao Kelly H.liu Weiwei Ding Xiongwei Niu Aiguo Ruan Pingchuan Tan Jianke Fan Shaoping Lu Zhengyi Tong liqun Cheng Wenfei Gong Yanghui Zhao jiabiao li Key Laboratory of Submarine Geosciences Second Institute of OceanographyMinistry of Natural Resources Southern Marine Science and Engineering Guangdong Laboratory Geology and Geophysics Program Department of Geosciences and Geological and Petroleum Engineering Missouri University of Science and Technology School of Earth Sciences and Engineering Sun Yat-sen University Key Laboratory of Marine Geology and Environment Institute of Oceanology Chinese Academy of Sciences

It has long been established that plastic flow in the asthenosphere interacts constantly with the overlying lithosphere and plays a pivotal role in controlling the occurrence of geohazards such as earthquakes and volcanic eruptions.Unfortunately,accurately characterizing the direction and lateral extents of the mantle flow field is notoriously difficult,especially in oceanic areas where deployment of ocean bottom seismometers(OBSs) is expensive and thus rare.In this study,by applying shear wave splitting analyses to a dataset recorded by an OBS array that we deployed between mid-2019 and mid-2020 in the South China Sea(SCS),we show that the dominant mantle flow field has a NNW-SSE orientation,which can be attributed to mantle flow extruded from the Tibetan Plateau by the ongoing Indian-Eurasian collision.In addition,the results suggest that E-W oriented flow fields observed in South China and the Indochina Peninsula do not extend to the central SCS.

关键词： mantle flow South China Sea Tibetan Plateau seismic anisotropy shear wave splitting

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

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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

The crustal nature of the northern Mozambique Ridge,Southwest Indian Ocean

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Acta Oceanologica Sinica 2021年第7期40卷 170-182页

作者： Nelta David Matsinhe Yong Tang Chun-Feng li jiabiao li Estevão Stefane Mahanjane He li Yinxia Fang Institute of Marine Geology and Resources Zhejiang UniversityZhoushan 316021China Key Laboratory of Submarine Geosciences Second Institute of OceanographyMinistry of Natural ResourcesHangzhou 310012China School of Oceanography Shanghai Jiao Tong UniversityShanghai 200240China Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai) Zhuhai 519080China College of Marine Science and Technology China University of GeosciencesWuhan 430074China College of Marine Geosciences Ocean University of ChinaQingdao 266100China Laboratory for Marine Mineral Resources Pilot National Laboratory for Marine Science and Technology(Qingdao)Qingdao 266237China Institute National Petroleum(INP) Maputo 4724Mozambique

The Mozambique Ridge(MOZR)is one of the basement high structures located in the Southwest Indian Ocean,parallel to the Southeast African continental margin.It was formed as a result of the tectono-magmatic evolution of the Gondwana breakup.The origin of the MOZR has been highly debated,with models suggesting either continental or oceanic origin.With new free-air gravity anomaly and multichannel seismic(MCS)reflection data,we present results of 2D density modeling along two seismic profiles acquired by R/V Xiangyanghong 10 at the northern Mozambique Ridge(N-MOZR)between 26°S and 28°S.We observed high free-air gravity anomaly and strong positive magnetic anomaly related to the emplaced seaward dipping reflectors(SDR)and high density lower crustal body(HDLCB),and high Bouguer gravity anomaly associated with the thinning of the continental crust underneath the N-MOZR over a distance of~82 km.This suggests a thinned and intruded continental crust bound by the Mozambique Fracture Zone(MFZ)that is characterized by gravity low and negative magnetic anomaly.This fracture zone marks the continent-ocean boundary(COB)while the N-MOZR is the transform margin high,i.e.,marks the continent-ocean transition(COT)of the Southern Mozambique margin,following the definition of transform margins.We suggest that the N-MOZR was formed by continental extension and subsequent breakup of the MFZ,accompanied by massive volcanism during the southward movement of the Antarctica block.The presence of SDR,HDLCB,and relatively thick oceanic crust indicates the volcanic nature of this transform margin.

关键词： crustal nature northern Mozambique Ridge seaward dipping reflection gravity modeling continent-ocean transition continent-ocean boundary

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扎染工艺下铜鼓纹样方巾盲盒设计

湖南包装 2024年第1期39卷 194-197页

作者：李嘉彪刘爽广西大学艺术学院广西南宁530004

针对当今盲盒设计形式乏味单一等问题,文章基于扎染工艺,将广西铜鼓纹样融合在盲盒设计中,先分别从文化价值和美学价值两个方面具体分析铜鼓纹样在方巾盲盒设计中的应用价值,然后通过对铜鼓纹样提取、解构及重组的方式对铜鼓纹样方巾进... 详细信息

针对当今盲盒设计形式乏味单一等问题,文章基于扎染工艺,将广西铜鼓纹样融合在盲盒设计中,先分别从文化价值和美学价值两个方面具体分析铜鼓纹样在方巾盲盒设计中的应用价值,然后通过对铜鼓纹样提取、解构及重组的方式对铜鼓纹样方巾进行多样化图案设计,最终采用扎染工艺进行铜鼓方巾的盲盒设计,以增强盲盒设计的民族性和多样性,为盲盒设计注入新的生命力。

关键词：扎染方巾铜鼓纹样盲盒