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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

Saddlepoint Approximation Method in Reliability Analysis:A Review

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Computer Modeling in Engineering & Sciences 2024年第6期139卷 2329-2359页

作者： Debiao Meng Yipeng Guo yihe xu Shiyuan Yang Yongqiang Guo Lidong Pan Xinkai Guo School ofMechanical and Electrical Engineering University of Electronic Science and Technology of ChinaChengdu611731China Institute of Electronic and Information Engineering of UESTC in Guangdong Dongguan523808China Glasgow College University of Electronic Science and Technology of ChinaChengdu611731China Beijing Research Institute of Mechanical&Electrical Technology Ltd.Beijing100083China

The escalating need for reliability analysis(RA)and reliability-based design optimization(RBDO)within engineering challenges has prompted the advancement of saddlepoint approximationmethods(SAM)tailored for such *** article offers a detailed overview of the general SAM and summarizes the method characteristics ***,recent enhancements in the SAM theoretical framework are ***,the mean value first-order saddlepoint approximation(MVFOSA)bears resemblance to the conceptual framework of the mean value second-order saddlepoint approximation(MVSOSA);the latter serves as an auxiliary approach to the *** distinction is rooted in the varying expansion orders of the performance function as implemented through the Taylor *** the saddlepoint approximation and third-moment(SATM)and saddlepoint approximation and fourth-moment(SAFM)strategies model the cumulant generating function(CGF)by leveraging the initial random moments of the *** their optimal application domains diverge,each method consistently ensures superior relative precision,enhanced efficiency,and sustained *** method elucidated is exemplified through pertinent RA or RBDO *** juxtaposing them against alternative strategies,the efficacy of these methods becomes *** outcomes proffered are subsequently employed as a foundation for contemplating prospective theoretical and practical research endeavors concerning *** main purpose and value of this article is to review the SAM and reliability-related issues,which can provide some reference and inspiration for future research scholars in this field.

关键词： Reliability analysis reliability-based design optimization saddlepoint approximation

Preliminary Results of Tomography from Permanent Stations in the Anhui Airgun Experiment

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Earthquake Research in China 2016年第3期30卷 405-417页

作者： Zhang Yunpeng Wang Baoshan Wang Weitao xu yihe Key Laboratory of Seismic Observation and Geophysical Imaging Institute of GeophysicsCEA

In order to explore the ability of airgun sources in imaging the crustal structure,we conducted an experiment along the Yangzte River at the section from Ma 'anshan to Anqing using an offshore airgun source( referred as the Anhui Airgun Experiment).During the experiment,the airgun source was fired 2973 times at 20 multiple shot points,while 109 permanent stations and 700 temporary stations( 11 profiles) were used to record the signal. For 20 multiple shot points,we picked up 335 P-wave arrivals at 52 permanent stations. Then we obtained the P-wave velocity structure of the crust beneath the southern tip of the Tancheng-Lujiang( Tan-Lu) fault. The preliminary result of P-wave velocity structure confirms the possibility of 3D body wave imaging using large volume airgun sources. The imaged velocity heterogeneity at a depth of 15 km is correlated to the geological settings. High velocity anomaly beneath the Qinling-Dabie orogenic belt could be explained by the ultrahigh-pressure metamorphic rocks in the deep region,while the low velocity anomaly at the Yangtze River region may correspond to the special background of mineralization.

关键词： Southern tip of the Tancheng-Lujiang fault Large volume airgun Phase picking Body-wave tomography

Some Thoughts on the Earthquake Science Experimental Site——The Underground Cloud Map

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Earthquake Research in China 2019年第1期33卷 1-8页

作者： CHEN Yong xu yihe CAI Huiteng LI Wen School of Earth Sciences and Engineering Nanjing University Institute of Earthquake Forecasting CEA Key Laboratory of Seismic Observation and Geophysical Imaging Institute of GeophysicsCEA Fujian Earthquake Agency Geophysical Exploration Center CEA

The Western Yunnan Earthquake Predication Test Site set up jointly by the China Earthquake Administration,the National Science Foundation Commission of America,and United States Geological Survey has played an important role in development of early earthquake research work in China. Due to various objective reasons, most of the predicted targets in the earthquake prediction test site have not been achieved,and the development has been hindered. In recent years, the experiment site has been reconsidered,and renamed the "Earthquake Science Experimental Site". Combined with the current development of seismology and the practical needs of disaster prevention and mitigation,we propose adding the "Underground Cloud Map"as the new direction of the experimental site. Using highly repeatable, environmentally friendly and safe airgun sources,we could send constant seismic signals,which realizes continuous monitoring of subsurface velocity changes. Utilizing the high-resolution 3-D crustal structure from ambient noise tomography,we could obtain 4-D (3-D space+1-D time) images of subsurface structures, which we termed the "Underground Cloud Map". The"Underground Cloud Map" can reflect underground velocity and stress changes,providing new means for the earthquake monitoring forecast nationwide,which promotes the conversion of experience-based earthquake prediction to physics-based prediction.

关键词： Earthquake Science Experimental Site The Underground Cloud Map 4-D seismology Airgun

Heterogeneous Mg isotopic composition of the early Carboniferous limestone: implications for carbonate as a seawater archive

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Acta Geochimica 2018年第1期37卷 1-18页

作者： Haoran Ma yihe xu Kangjun Huang Yuanlin Sun Shan Ke Yang Peng Xianguo Lang Zhen Yan Bing Shen Key Laboratory of Orogenic Belts and Crustal Evolution MOE School of Earth and Space Sciences Peking University State Key Laboratory of Geological Processes and Mineral Resources China University of Geosciences

Carbonate precipitation and hydrothermal reaction are the two major processes that remove Mg from *** isotopes are significantly(up to 5%)fractionated during carbonate precipitation by preferential incorporation of ^(24)Mg,while hydrothermal reactions are associated with negligible Mg isotope fractionation by preferential sequestration of^( 26)***,the marine Mg cycle could be reflected by seawater Mg isotopic composition(δ^(26)Mg_(sw)),which might be recorded in marine ***,carbonates are both texturally and compositionally heterogeneous,and it is unclear which carbonate component is the most reliable for reconstructing δ^(26)Mg_(sw).In this study,we measured Mg isotopic compositions of limestone samples collected from the early Carboniferous Huangjin Formation in South *** on petrographic studies,four carbonate components were recognized:micrite,marine cement,brachiopod shell,and *** four components had distinct δ^(26)Mg:(1)micrite samples ranged from -2.86% to -2.97%;(2)pure marine cements varied from -3.40% to -3.54%,while impure cement samples containing small amount of Rugosa coral skeletons showed a wider range(-3.27% to-3.75%);(3)values for the mixture component were-3.17% and -3.49%;and (4)brachiopod shells ranged from -2.20% to -3.07%,with the thickened hinge area enriched in ^( 24)*** to having multiple carbonate sources,neither the micrite nor the mixture component could be used to reconstruct δ^(26)Mg_(sw).In addition,the marine cement was homogenous in Mg isotopes,but lacking the fractionation by inorganic carbonate precipitation that is prerequisite for the accurate determination of δ^(26)Mg_(sw).Furthermore,brachiopod shells had heterogeneous C and Mg isotopes,suggesting a significant vital effect during ***,the heterogeneous δ^(26)Mg of the Huangjin limestone makes it difficult to reconstruct δ^(26)Mg_(sw)using bulk carbonate/calcareous ***,δ^(26)Mg_(sw)was only slightly affected by

关键词： Seawater Mg isotopic composition Limestone Fossil Micrite Cement

Attenuation Characteristics of Earthquake Ground Motion for Large Volume Airgun

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Earthquake Research in China 2019年第4期33卷 544-556,I0001页

作者： CAI Huiteng CHEN Yong JIN Xing xu yihe LI Wen School of Earth Sciences and Engineering Nanjing UniversityNanjing 210046China Fujian Earthquake Agency Fuzhou 350003China Institute of Geophysics CEABeijing 100081China Geophysical Exploration Center CEAZhengzhou 450003China

In order to further deepen the understanding of seismic wave propagation characteristics induced by the large volume airgun source,experimental data from multiple fixed excitation points in Fujian Province were used to obtain the equivalent single excitation high signal-to-noise ratio velocity and displacement records through linear stacking and simulation *** the peak displacements of different epicentral distances were used to calculate the equivalent magnitude of the airgun source excitation at different fixed excitation points so as to establish the attenuation relationship between equivalent magnitude,epicenter distance and velocity *** results show that:①Within 270 km of epicentral distance,for the large-volume airgun’s single shot,the peak velocity range is about 700-4 nm/s,and the peak displacement range is about 200.0-0.2 nm;②The equivalent magnitude of the P-wave from the airgun source with a total capacity of 8,000 in 3 is 0.181-0.760,and the equivalent magnitude of the S-wave is *** contrast,the equivalent magnitude of the P-wave from the airgun source with a total capacity of 12,000 in 3 is 0.533-0.896,and the equivalent magnitude of the S-wave is *** S-wave energy is greater than the P-wave energy,and the excitation efficiency varies greatly with different excitation environment;③The peak velocity increases with the equivalent magnitude,and decreases with the epicentral *** vertical component of the P-wave peak velocity is the largest among those three components,while the S-wave has the smallest vertical component and similar horizontal ***,our research can provide an important basis for the quantitative judgment of the seismic wave propagation distance using the airgun and the design of the observation system in deep exploration or monitoring with airgun.

关键词： Large-volume airgun source Velocity peak value Displacement peak value Equivalent magnitude Attenuation characteristics

Review of the 2018 Palu Tsunami: Disaster Behavior and Reflections on Disaster Management

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Earthquake Research in China 2019年第1期33卷 153-163页

作者： HU Jiupeng CHEN Yong LI Wen xu yihe CAI Huiteng Seismic Observation and Geophysical Imaging Laboratory Institute of GeophysicsCEA School of Earth Science and Engineering Nanjing University Geophysical Exploration Center China Earthquake Administration Fujian Earthquake Agency

The 2018 Palu M_W7.5 earthquake and tsunami attracted geophysicists' attention for its strike slip focal mechanism and magnitude. We inspected the details of this disaster and discussed its particularity and possible causations. The submarine landslide and special terrain conditions could have contributed to the unusual size of the tsunami. The early warning system and the post disaster response is also reviewed. Efficient social warnings and broadcast systems along with good maintenance is essential. We also found that enhancing publics scientific literacy is the most important way to reduce disaster damage and casualties. Moreover, social conditions and rebuilding difficulties post tsunami are related as reference resources for future disaster management strategies.

关键词： Palu tsunami Disaster loss Tsunami early warning Disaster management

An interactive program on digitizing historical seismograms

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An interactive program on digitizing historical seismograms

球对称有限水体气泡振荡模型及其对陆地水体气枪研究的意义

中国科学院地质与地球物理研究所2014年度（第14届）学术年会

作者： yihe xu Tao xu State Key Laboratory of Lithospheric Evolution Institute of Geology and GeophysicsChinese Academy of Sciences University of Chinese Academy of Sciences

Retrieving information from analog seismograms is of great importance since they are considered as the unique sources that provide quantitative information of historical earthquakes. We present an algorithm for automatic digitization of the seismograms as an inversion problem that forms an interactive program using Matlab s GUI. The program integrates automatic digitization with manual digitization and users can easily switch between the two modalities and carry out different combinations for the optimal *** examples about applying the interactive program are given to illustrate the merits of the method.

关键词： Digitization Inversion problem Matlab s GUI Priori information

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地球物理学报 2022年第9期65卷 3374-3385页

作者：徐逸鹤王宝善王伟涛中国地震局地球物理研究所北京100081 英国剑桥大学地球科学系剑桥CB30EZ 爱尔兰都柏林高等研究院宇宙物理学学院地球物理学分部都柏林D02Y006 中国科学技术大学地球和空间科学学院合肥230026

在陆内水体内激发气枪震源,利用其气泡振荡产生的地震波可以研究地下结构及速度变化.与海洋激发环境不同,陆内有限水体会影响气泡的振荡过程.本文利用有限元方法,对球对称情况下气泡在有限水体内的振荡过程进行了数值模拟分析,发现气枪... 详细信息

在陆内水体内激发气枪震源,利用其气泡振荡产生的地震波可以研究地下结构及速度变化.与海洋激发环境不同,陆内有限水体会影响气泡的振荡过程.本文利用有限元方法,对球对称情况下气泡在有限水体内的振荡过程进行了数值模拟分析,发现气枪震源在陆内水体内的气泡振荡存在临界大小,与气枪激发时产生的激波有关.模拟结果表明,水体较大时(半径大于100 m),可以继续使用无限水体模型;当水体较小时(半径小于50 m),固液边界反射的激波会改变气泡处的压力,进而改变气泡振荡过程,显著地提高气泡振荡的频率,降低振荡的幅度.相关数值模拟结果与实验观测相符,为陆内小水体中气枪的高频源场信号特征提供了合理的解释.基于有限水体的气泡振荡过程分析有助于提升对陆内水体气枪激发过程的理解,为气枪选址、设计、优化提供理论依据.

关键词：气枪有限水体震源主动源气泡振荡