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3D S-wave velocity structure of the Ningdu basin in Jiangxi province inferred from ambient noise tomography with dense array

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Earthquake Research Advances 2023年第1期3卷 70-80页

作者： Long Teng Xiangteng Wang Chunlei Fu Feng Bao Jiajun Chong Sidao Ni Zhiwei Li School of Earth and Space Sciences University of Science and Technology of ChinaHefei230026China Nanjing Center China Geological SurveyNanjing210016China East China University of Technology Nanchang330013China State Key Laboratory of Geodesy and Earth's Dynamics Innovation Academy for Precision Measurement Science and TechnologyWuhan430077China Beijing Institute of Spacecraft Environment Engineering Beijing100094China

The Ningdu basin,located in southern Jiangxi province of southwest China,is one of the Mesozoic basin groups which has exploration prospects for geothermal energy.A study on the detailed velocity structure of the Ningdu basin can provide important information for geothermal resource *** this study,we deployed a dense seismic array in the Ningdu basin to investigate the 3D velocity structure and discuss implications for geothermal exploration and geological *** on the dense seismic array including 35 short-period(5 s-100 Hz)seismometers with an average interstation distance of~5 km,Rayleigh surface wave dispersion curves were extracted from the continuous ambient noise data for surface wave tomographic *** velocity tomography was conducted and the 3D S-wave velocity structure was inverted by the neighborhood *** results revealed obvious low-velocity anomalies in the center of the basin,consistent with the low-velocity Cretaceous sedimentary *** basement and basin-controlling fault can also be depicted by the S-wave velocity *** obvious seismic interface is about 2 km depth in the basin center and decreases to 700 m depth near the basin boundary,suggesting spatial thickness variations of the Cretaceous *** fault features of the S-wave velocity profile coincide with the geological cognition of the western boundary basincontrolling fault,which may provide possible upwelling channels for geothermal *** study suggests that seismic tomography with a dense array is an effective method and can play an important role in the detailed investigations of sedimentary basins.

关键词： Ambient noise tomography dense array S-wave velocity structure Ningdu basin Geothermal energy

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Estimating the site effects in Luoyang basin using horizontal-to-vertical spectral ratio method from a short-period dense array

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Earthquake Science 2018年第5期31卷 272-280页

作者： Yujuan Tan Yunhao Wei Yonghong Duan Fuyun Wang Geophysical Exploration Center China Earthquake Administration Institute of Geology and Geophysics Chinese Academy of Sciences

The influence of local site effects on seismic ground motions is an important issue in seismic hazard assessment and earthquake resistant design. Determining site effects in densely populated cities built on basins can help to reduce the earthquake hazard. Site effects of Luoyang basin are estimated by the horizontal-to-vertical spectral ratio(HVSR) method using ambient noise records from a short-period dense array. The sites in Luoyang basin are sorted into three types according to the pattern of the HVSR curves. There are cases with a single clear peak, two clear peaks, and an unclear low frequency peak or multiple peaks, which correspond to there being one large impedance contrast interface, two large interfaces, and a moderate one beneath the sites, respectively. The site effects characterized by fundamental frequency from HVSR curves are affected by underlying sedimentary layers and depth of sedimentary basement. According to our results, the existence of thick sediment layer obviously lowers the fundamental frequency to the period range from 2 to 4 s in the downtown area of Luoyang city. The ground motion will amplify when through the sites and the buildings with height of 20–50 floors can resonate at the similar frequency domain. Site effects estimation using HVSR method from a short-period dense array is an effective technique in areas of moderate seismic risk where strong motion recordings are lacking, such as the Luoyang basin.

关键词： site effects horizontal to vertical spectral ratio dense array Luoyang basin

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Shallow velocity structure of the Luoyang basin derived from dense array observations of urban ambient noise

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Earthquake Science 2018年第5期31卷 252-261页

作者： Ming Zhou Xiaofeng Tian Fuyun Wang Yunhao Wei Hailiang Xin Geophysical Exploration Center China Earthquake Administration

Determining the shallow structure of a sediment basin is important when evaluating potential seismic hazards given that such basins can significantly amplify seismic energy. The Luoyang basin is located in the western He’nan uplift and is a Meso-Cenozoic depression basin. To characterize the shallow structure of the basin, we develop a model of the shallow high-resolution three-dimensional(3D)shear-wave velocity structure of the basin by applying ambient noise tomography to a dense array of 107 portable digital seismometers deployed over the basin. More than 1,400 Rayleigh-wave dispersion curves for periods in the range 0.5–5 s are extracted. The 3D variations of shear-wave velocity in the shallow crust are inverted using a direct surface-wave tomographic method with period-dependent ray tracing, with all the surface-wave group-velocity dispersion data being inverted simultaneously. The results show that in the shallow crust of the study area, the velocity distribution corresponds to surface geology and geological features. The Luoyang basin exhibits a low shear-wave velocity feature that is consistent with the distribution of sediment in the region,while the Xiongershan and Songshan uplifts exhibit higher shear-wave velocity structures. The results provide a shallow high-resolution 3D velocity model that can be used as a basis for simulation of strong ground motion and evaluation of potential seismic hazards.

关键词： ambient noise tomography three-dimensional velocity structure Luoyang basin dense array

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Topography effect on ambient noise tomography using a dense seismic array

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Earthquake Science 2018年第5期31卷 291-300页

作者： Shuang Wang Xinlei Sun State Key Laboratory of Isotope Geochemistry Guangzhou Institute of GeochemistryChinese Academy of SciencesGuangzhou 510640China University of Chinese Academy of Sciences Beijing 100049China

With the rapid increase of dense seismic array deployment, more and more ambient noise studies have been applied on short period surface waves tomography. For arrays with inter-station distance of several hundred meters,the effect of surface topography has to be considered. In this study, we investigate topography effect on ambient noise surface wave tomography using synthetic data from different topographic models. Our travel times are synthetized considering surface topography, and shear wave inversions are performed by incorporating and not incorporating topography respectively. Our inversion results suggest that topography does affect subsurface shear wave velocity inversion. If topography is not considered, although the pattern of the structure may be recovered reasonably well, the depth distribution of velocity structure can be distorted. The maximum distortion depth is generally correlated with the relief of the topography and the amplitude of the velocity anomalies. Finally, our example of real data inversion in a mountain area demonstrates good correlation between shear velocity and the geological settings, as well as the core sample in that area.

关键词： topography effect dense array ambient noise tomography

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A pilot project of ambient noise tomography on a dense seismic array in Ji'nan urban area

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Earthquake Science 2018年第5期31卷 262-271页

作者： Feng Liang Lei Gao Zhihui Wang Tao Wang Kai Liu Sinoprobe Center-China Deep Exploration Center Chinese Academy of Geological Sciences

In this study, we conducted ambient noise tomography(ANT), with 33-day data, to investigate the nearsurface shear-velocity structure in downtown Ji’nan, Shandong Province, China. The cross-correlation functions with quiet clear Rayleigh waves are obtained with more symmetrical energy distribution which indicates that strong human activities, such as moving vehicles and municipal engineering construction, can produce approximately isotropic distribution of noise sources for high-frequency signals. The direct surfacewave tomographic method with period-dependent ray-tracing is used to invert all surface-wave dispersion data in the period band 0.2–1.5 s simultaneously for 3D variations of shear-velocity structure. The study result can help us better understand the local geologic structures, evaluate the distribution and geometry of the fracture-karst media, and assess hazards of the concealed active fault and its effect on the springs in the future.

关键词： ambient noise shear wave velocity urban geophysics urban underground space dense array

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Quick Phase Identification for dense Seismic array with Aid from Long Term Phase Records of Co-located Sparse Permanent Stations

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Earthquake Research in China 2020年第3期34卷 328-342页

作者： CHEN Yini LI Jun WANG Zhenjie ZHAO Mengqi YU Tiehong LI Danning YU Junyi WANG Weitao Zhejiang Earthquake Agency Hangzhou 310013China Key Laboratory of Earthquake Source Physics Institute of GeophysicsChina Earthquake AdministrationBeijing 100086China Yunnan Earthquake Agency Kunming 650224China

The phase identification and travel time picking are critical for seismic tomography,yet it will be challenging when the numbers of stations and earthquakes are *** here present a method to quickly obtain P and S travel times of pre-determined earthquakes from mobile dense array with the aid from long term phase records from co-located permanent *** records for 1768 M≥2.0 events from 2011 to 2013 recorded by 350 Chinarray stations deployed in Yunnan Province are processed with an improved AR-AIC method utilizing cumulative envelope and *** reference arrivals are predicted based on phase records from 88 permanent stations with similar spatial coverage,which are further refined with ***,718573 P picks and 512035 S picks are obtained from mobile stations,which are 28 and 22 times of those from permanent stations,*** comparing the automatic picks with manual picks from 88 permanent stations,for M≥3.0 events,81.5%of the P-pick errors are smaller than 0.5 second and 70.5%of S-pick errors are smaller than1 *** events with a lower magnitude,76.5%P-pick errors fall into 0.5 second and 69.5%S-pick errors are smaller than 1 ***,the Pn and Sn phases are easily discriminated from directly P/S,indicating the necessity of combining traditional auto picking and integrating machine learning method.

关键词： Phase picking Travel time dense array Spatial overlap

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Illuminating high-resolution crustal fault zones using multi-scale dense arrays and airgun source

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Earthquake Research Advances 2021年第1期1卷 10-18页

作者： Hongfeng Yang Yaohui Duan Junhao Song Weitao Wang Wei Yang Xiaofeng Tian Baoshan Wang Earth System Science Programme Faculty of ScienceThe Chinese University of Hong KongHong KongChina Shenzhen Research Institute The Chinese University of Hong KongShenzhenChina Institute of Geophysics China Earthquake AdministrationBeijingChina Center of Geophysical Exploration China Earthquake AdministrationZhengzhouChina School of Earth and Space Sciences University of Science and Technology of ChinaHefeiChina

High-resolution imaging of fault zone structure and its temporal changes can not only advance our understanding of earthquake physics,but is also critical for better seismic hazard preparation and *** the past a few years,we deployed multi-scale dense arrays across the Chenghai fault system in Binchuan,Yunnan,*** first array consisted of 381 intermediate-period three-component seismometers with an average station spacing of~2 *** array has been deployed in the field for~3 months in 2017 and recorded numerous local and teleseismic *** time analyses based on teleseismic earthquakes and an airgun source in the region indicated clear signature of low-velocity fault zones in the southern branch of the Chenghai fault *** 2018 we deployed two other linear arrays using the same instruments with much smaller inter-station spacing,e.g.30-50 m,across the southern branch the Chenghai *** profile lengths were 8 and 5 km,*** sections of the airgun source on the two linear arrays clearly marked a low-velocity zone(LVZ)within the southern array but no such signature in the northern array,suggesting along-strike variation of the *** the instruments within our dense arrays had an intermediate frequency band,we demonstrated that they were capable of characterizing crustal structure with techniques commonly applied to broadband signals such as receiver *** our best knowledge,this was the first time to have multi-scale across-fault dense arrays with three-component seismometers in such *** results lay out the pavement to comprehensively investigate fault zone structures as well as to derive subsurface structural changes using dense arrays and the airgun source.

关键词： Fault zone Temporal changes dense array Airgun source

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Multiple seismological evidences of basin effects revealed by array of Binchuan(ABC), northwest Yunnan, China

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Earthquake Science 2018年第5期31卷 281-290页

作者： Yihe Xu Baoshan Wang Weitao Wang Bo Zhang Tianwei Sun Key Laboratory of Seismic Observation and Geophysical Imaging Institute of GeophysicsChina Earthquake Administration School of Earth Sciences and Engineering Nanjing University School of Earth and Space Sciences University of Science and Technology of China

dense array seismology, which is characterized by large number, densely deployed autonomous geophone/seismographs, has received great concerns worldwide recently, especially after the great success of dense array in Long Beach. One of the biggest curiosity is that if the great success in Long Beach is replicable in China. Hence, we analyze the seismic records from a dense array in Binchuan basin, Yunnan province, which consists of three-component short-period seismographs of three most common domestic models. The Binchuan basin is located near the intersection between the Chenghai-Binchuan fault and the Red River fault,with the latter being the major fault accommodating significant tectonic deformation resulting from eastern extrusion of the Tibetan plateau. Both faults pose serious seismic threats to local residents in Binchuan basin. Basinrange differences, faults, local earthquakes, and a Fixed Airgun Seismic Transmitting Station(FASTS), make the Binchuan basin a perfect experiment site for dense array experiment. The array is named array of Binchuan(ABC)and the main target is imaging the shallow crustal structure,especially the structure of the basin. To examine the monitoring capability of ABC, we analyze the seismograms to check if they can reveal the basin, the most significant geological feature in the area. Power spectral density analysis,travel time and amplitude analysis of FASTS signals, and amplitude analysis of earthquakes and noise cross-correlation functions are used in the analysis. All the results show correlation with the basin and clear difference between basin and non-basin area. Therefore, the preliminary results support that the ABC has the potential to provide constraints on local structures.

关键词： array of Binchuan dense array basin effects

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Near-surface structure from ambient-noise tomography and horizontal-to-vertical spectral ratio beneath the Nankou-Sunhe fault

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Earthquake Science 2020年第5期33卷 232-238页

作者： Yuting Zhang Hongyi Li Yanzhen Li Zhijie Wei Zeyu Ma Huiying Ge Tongli Wang Yafen Huang Min Liu School of Geophysics and Information Technology China University of GeosciencesBeijing 100083China Shanghai Sheshan National Geophysical Observatory Shanghai 201602China Beijing Earthquake Agency Beijing 100080China

Active faults pose a great threat to urban *** the largest NW-trend active fault in Beijing area,the Nankou-Sunhe fault plays an important role in earthquake disaster and city *** this study,we collect continuous ambient noise data recorded by 43 temporary short-period seismograph between September 21th to October 12th 2019 to investigate the near-surface structure beneath the Nankou-Sunhe fault by using ambient noise tomography(ANT)and horizontal-to-vertical spectral ratio(HVSR)*** ambient noise processing,fundamental-mode Rayleigh wave signals are clearly observed in the frequency band of 0.4-2.5 *** direct surface-wave inversion algorithm is applied to calculate the 3D shear-wave velocity *** results show that there is a sharp velocity contrast across the Nankou-Sunhe fault,with low velocities down to about 2 km on the hanging wall and high velocity on the footwall of the *** to the geological investigation,the low velocities are related to thicker sediments and Jurassic volcanic rock below which are the cap rock of the hydrothermal *** the HVSR analysis,the HVSR curves of the sites near the fault shows double-peak,one less than 1 Hz and the other centered 7 *** converting frequency to depth by the empirical equation,the results show that the thickness of sediments is thinned from southwest to northeast,which generally agrees well to field *** results provide high-resolution near-surface structure for future study on disaster risk reduction and urban planning.

关键词： ambient noise tomography horizontal-to-vertical spectral ratio dense array Nankou-Sunhe fault

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Recent advances in earthquake monitoring I:Ongoing revolution of seismic instrumentation

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Earthquake Science 2021年第2期34卷 177-188页

作者： Zefeng Li Laboratory of Seismology and Physics of Earth’s Interior School of Earth and Space SciencesUniversity of Science and Technology of ChinaHefeiAnhui230026China Mengcheng National Geophysical Observatory University of Science and Technology of ChinaMengcheng233500China

Seismic networks have significantly improved in the last decade in terms of coverage density,data quality,and instrumental ***,revolutionary advances in ultra-dense seismic instruments,such as nodes and fiber-optic sensing technologies,have recently provided unprecedented high-resolution data for regional and local earthquake *** arrays have characteristics such as easy installation and flexible apertures,but are limited in power efficiency and data storage and thus most suitable as temporary ***-optic sensing techniques,including distributed acoustic sensing,can be operated in real time with an in-house power supply and connected data storage,thereby exhibiting the potential of becoming next-generation permanent ***-optic sensing techniques offer a powerful way of filling the observation gap particularly in submarine *** these technological advancements,various challenges ***,the data characteristics of fiber-optic sensing are still ***,it is challenging to construct software infrastructures to store,transfer,visualize,and process large amount of seismic ***,innovative detection methods are required to exploit the potential of numerous *** improved knowledge about data characteristics,enhanced software infrastructures,and suitable data processing techniques,these innovations in seismic instrumentation could profoundly impact observational seismology.

关键词： earthquake monitoring seismic instrumentation dense array distributed acoustic sensing.

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