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Structure of the mantle transition zone in the central and western parts of the North China Craton using the receiver function 3D Kirchhoff migration method

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Science China Earth Sciences 2024年第9期67卷 2783-2795页

作者： Min ZHU Qingju WU Jieyuan NING Ruiqing ZHANG Institute of Geophysics China Earthquake AdministrationBeijing 100081China Institute of Theoretical and Applied Geophysics Peking UniversityBeijing 100871China

Using data from the regional broadband dense temporary array deployed by the ChinArray project,we applied the three-dimensional(3D)Kirchhoff migration method of the teleseismic P-wave receiver function to investigate discontinuity structures of the mantle transition zone(MTZ)in the central and western parts of the North China Craton(NCC)using a highresolution 3D velocity model of the East Asian *** results show that the 410-km discontinuity beneath the Datong Volcano is depressed by~10 km,indicating the presence of a high-temperature anomaly near the depth of 410 km,which is likely related to small-scale mantle upwelling caused by the dehydration of the stagnant Pacific Plate in the *** upwelling of hot material provides a heat source for surface magmatic *** the Bohai Bay Basin,significant subsidence of the 660-km discontinuity is observed,and the transition zone here is extensively ***’s suggested that the anomalies in this region are related to the stagnation of the Pacific slab in the *** the thickness of the transition zone west of the North-South Gravity Lineament appears normal,we propose that the subducting front of the Pacific slab did not cross the gravity lineament in the *** comparison,the small-scale subsidence of the 660-km discontinuity and the thickening of the MTZ observed north of the Hannuoba Volcano likely indicate that the slab crossed the gravity lineament at its turning point and remained in the ***,a local thickening of the MTZ is observed in the Dabie orogenic belt of the Qinling *** is believed to be a combined effect of lithospheric delamination into the transition zone in the lower Yangtze region and the stagnation of the Pacific Plate.

关键词： North China Craton Mantle transition zone Receiver function migration Datong Volcano

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Intrinsic and scattering attenuations of the Sichuan-Yunnan region in China from S coda waves

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earthquake Science 2024年第1期37卷 51-66页

作者： Tian Li Lei Zhang Xiaodong Song Qincai Wang Xinyu Jiang Jinchuan Zhang Hanlin Chen SinoProbe Laboratory School of Earth and Space SciencesPeking UniversityBeijing 100871China Hebei Hongshan National Observatory on Thick Sediments and Seismic Hazards Peking UniversityBeijing 100871China Institute of earthquake Forecasting China Earthquake AdministrationBeijing 100036China earthquake Agency of Jiangsu Province Nanjing 210014China

Seismic attenuation is a fundamental property of the Earth's *** structure for the complicated geological structures with strong seismicity in the Sichuan-Yunnan region is poorly *** this study,we collected 108,399 waveforms of 11,517 local small earthquakes with magnitudes between 1.5 and 3.5 from January 2014 to September 2021 in the Sichuan-Yunnan region and its adjacent *** employed an envelope inversion technique for separating the intrinsic and scattering attenuations of the S coda wave,and obtained the intrinsic and scattering attenuation structures for frequencies between 0.25 and 8.00 *** attenuation structures correlate well with the geological units,and some major faults mark the attenuation variations where historic large earthquakes have *** regional average attenuation shows a negative frequency *** average scattering attenuation has a faster descending rate than the average intrinsic attenuation,and is dominant at low frequencies,while at high frequencies the average intrinsic attenuation is *** lateral variation in the intrinsic attenuation is consistent with the variation in heat flow,the scattering attenuation may be related to the scatter distribution and *** total attenuation is consistent with the previous studies in this region,and the separate intrinsic and scattering attenuation may be useful in understanding regional tectonics and important in earthquake prevention and disaster reduction.

关键词： Intrinsic attenuation scattering attenuation Sichuan-Yunnan region

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A review of geophysical studies on the Mongolian Plateau

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earthquake Science 2024年第3期37卷 224-240页

作者： Lei Zhang Zhouchuan Huang Xiaodong Song Qingju Wu SinoProbe Laboratory School of Earth and Space SciencesPeking UniversityBeijing 100871China Hebei Hongshan National Observatory on Thick Sediments and Seismic Hazards Peking UniversityBeijing 100871China School of Earth Sciences and Engineering Nanjing UniversityNanjing 210023China Institute of Geophysics China Earthquake AdministrationBeijing 100081China

The Mongolian Plateau in Central Asia is an intracontinental tectonic system far from active plate *** its distance from these boundaries,the plateau is characterized by intense crustal deformation accompanied by voluminous Cenozoic volcanism and active modern ***,the intraplate deformation mechanism has long been debated owing to the scarcity of observations and contradictions between different *** recent years,growing geophysical studies have been conducted on the Mongolian Plateau,providing constraints on its lithospheric structure and ***,we review the geophysical research on the Mongolian Plateau over the last decade,including seismological,geodetic,gravity,magnetotelluric,and geodynamic *** review aims to(a)describe crustal and mantle structures based on multiscale seismic images;(b)describe deformation patterns based on seismic anisotropy,focal mechanisms,and global positioning system(GPS)observations;and(c)discuss the mechanisms behind intraplate deformation,volcanism,and seismic activity across the Mongolian *** images show that the crustal structure of the plateau has significant east-west *** blocks in the western Mongolian Plateau have thick crusts,including the Altai Mountains,Hovsgol Rift,and Hangay *** lithospheric deformation across the Mongolian Plateau has strong lateral variation,with NE-SW shortening in the Altai Mountains and W-E or NW-SE shear deformation in the Hangay Dome region and the eastern *** varied deformation may result from the superposition of multiple mechanisms,including far-field stress in the Altai Mountains,mantle upwelling,and mantle flow in the Hangay Dome ***,it is difficult to identify the geodynamics of the formation of the entire Mongolian Plateau because the deformation is too complicated,and the present models are not sufficient and are always ***,this review encompasses recent advances in seismic observa

关键词： Mongolian Plateau Central Asia seismic tomography crust-mantle structure intraplate deformation

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Crustal and uppermost mantle structure of the northeastern Qinghai-Xizang Plateau from joint inversion of surface wave dispersions and receiver functions with P velocity constraints

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earthquake Science 2024年第2期37卷 93-106页

作者： Pei Zhang Xiaodong Song Jiangtao Li Xingchen Wang Xuezhen Zhang Institute of Geophysics China Earthquake AdministrationBeijing 100081China The Second Monitoring and Application Center China Earthquake AdministrationXi'an 710054China Institute of Theoretical and Applied Geophysics School of Earth and Space SciencesPeking UniversityBeijing 100871China Department of Geophysics School of Geodesy and GeomaticsWuhan UniversityWuhan 430079China

Lithospheric structure beneath the northeastern Qinghai-Xizang Plateau is of vital significance for studying the geodynamic processes of crustal thickening and expansion of the Qinghai-Xizang Plateau. We conducted a joint inversion of receiver functions and surface wave dispersions with P-wave velocity constraints using data from the Chin Array Ⅱ temporary stations deployed across the Qinghai-Xizang Plateau. Prior to joint inversion, we applied the H-κ-c method(Li JT et al., 2019) to the receiver function data in order to correct for the back-azimuthal variations in the arrival times of Ps phases and crustal multiples caused by crustal anisotropy and dipping interfaces. High-resolution images of vS, crustal thickness, and vP/vSstructures in the Qinghai-Xizang Plateau were simultaneously derived from the joint inversion. The seismic images reveal that crustal thickness decreases outward from the Qinghai-Xizang Plateau. The stable interiors of the Ordos and Alxa blocks exhibited higher velocities and lower crustal vP/vSratios. While, lower velocities and higher vP/vSratios were observed beneath the Qilian Orogen and Songpan-Ganzi terrane(SPGZ), which are geologically active and mechanically weak, especially in the mid-lower *** or thermal erosion of the lithosphere triggered by hot asthenospheric flow contributes to the observed uppermost mantle low-velocity zones(LVZs) in the SPGZ. The crustal thickness, vS, and vP/vSratios suggest that whole lithospheric shortening is a plausible mechanism for crustal thickening in the Qinghai-Xizang Plateau, supporting the idea of coupled lithospheric-scale deformation in this region.

关键词： joint inversion receiver functions surface waves crustal thickness vP/vS ratio NE Qinghai-Xizang Plateau

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Characteristics and origin of mafic and ultramafic xenoliths in trachyandesite lavas from Heikongshan volcano,Tengchong,Yunnan Province,China

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Science China Earth Sciences 2010年第9期53卷 1295-1306页

作者： YU HongMei, LIN ChuanYong, SHI LanBin, XU JianDong & CHEN XiaoDe Institute of Geology, China earthquake Administration, Beijing 100029, China Institute of Geology China Earthquake Administration Beijing China

The trachyandesite lavas from Heikongshan volcano of the Tengchong volcanic cluster, Yunnan Province contain relatively abundant mafic and ultramafic small xenoliths comprising mainly gabbro, pyroxenite and rare lherzolites, all less than 2.5 cm in size. Gabbro xenoliths are characterized by "open" texture represented by relatively abundant vesicles and ground-mass fillings, while pyroxenite xenoliths are characterized by equigranular and poikilitic texture. Their mineral compositions (clinopyroxene ± orthopyroxene ± plagioclase) are similar to those of phenocrysts in lavas, and their equilibration temperature (1000-1125°C) is consistent with the crystallization temperature of the phenocrysts (998-1108°C). Thus, the textures and compositions of these xenoliths are different from those of lower crustal and mantle xenoliths, and were derived from the magma chamber. Among them, the gabbroic xenoliths come from the crystal-bubble-liquid zone at the top of the magma reservoir, while the pyroxenite xenoliths come from the cumulates in the bottom of magma reservoir. The studied single lherzolite xenolith with porphyroclastic texture has similar mineral compositions to the mantle xenoliths from eastern China, and is considered to be of upper mantle origin. It was brought into magma reservoir by replenishment magma, and might have experienced a cooling event before eruption. The formation of xenoliths in trachyandesite flows largely reflects the ascent, storage, evolution and eruption processes of magma.

关键词： magma chamber xenoliths geothermo-barometry trachyandesite Heikongshan volcano Tengchong

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First Discovery of North-South Striking Normal Faults near the Potential Eastern End of Altyn Tagh Fault

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Journal of Earth Science 2018年第1期29卷 182-192页

作者： Bo Zhang Daoyang Yuan Wengui He Wei Pang Pengtao Wang Ming Wu Lanzhou Institute of Seismology China Earthquake Administration Lanzhou 730000 China Institute of Geology China Earthquake Administration Beijing 100029 China Second Monitoring and Application Center China Earthquake Administration Xi'an 710054 China

The Altyn Tagh fault is the northern boundary of Tibetan Plateau. As one of the most well-known strike-slip fault in the world, great achievements on tectonic deformation and Late Qua- ternary slip rate have been made. However, there is a long-lasting debate on whether the Altyn Tagh fault extends into the Jinta Basin or even eastward. In this paper, we use satellite image interpretation, field investigation, trench excavation, and optical stimulated luminescence dating to study newly found NS striking scarps in the eastern end of Jinta Nan Shan. The results are as follows： firstly, a group of normal faults develop on terrace T2 of Heihe River, the total length amounts to -40 km, total scarp height is 304-5 m; secondly, four paleoseismic events have been interpreted from three trenches, approximate ages of events are 79.97±19.14 ka BP, 62.55±13.10~55.41±10.77 ka BP, before 16.89±2.08 ka BP, 8.52±1.49 ka BP, respectively; thirdly, just like NS normal faults in the western end of Altyn Tagh fault, the newly found NS extensional faults are likely the terminating tectonics of the eastern end of Altyn Tagh fault, the large Altyn Tagh fault may end in the eastern end of Jinta Nan Shan.

关键词： Altyn Tagh fault normal fault Jinta Nan Shan fault Heihe River paleoseismic events.

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earthquake simulator tests and associated study of an 1/6-scale nine-story RC model

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earthquake Engineering and Engineering Vibration 2007年第3期6卷 281-288页

作者：孙景江王涛齐虎 Institute of Engineering Mechanics China Earthquake Administration Harbin 150080 China Heilongjiang Institute of Science and Technology Harbin 150080 China

earthquake simulator tests of a 1/6-scale nine-story reinforced concrete frame-wall model are described in the paper. The test results and associated numerical simulation are summarized and discussed. Based on the test data, a relationship between maximum inter-story drift and damage state is established. Equations of variation of structural characteristics （natural frequency and equivalent stiffness） with overall drifts are derived by data fitting, which can be used to estimate structural damage state if structural characteristics can be measured. A comparison of the analytical and experimental results show that both the commonly used equivalent beam and fiber element models can simulate the nonlinear seismic response of structures very well. Finally, conclusions associated with seismic design and damage evaluation of RC structures are presented.

关键词： earthquake simulator test reinforced concrete structure nonlinear analysis drift ratio

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Magmatic Processes of Ashi Volcano, Western Kunlun Mountains, China

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Acta Geologica Sinica(English Edition) 2014年第2期88卷 530-543页

作者： YU Hongmei XU Jiandong ZHAO Bo SHEN Huanhuan LIN Chuanyong Key Laboratory of Active Tectonics and Volcano Institute of GeologyChina Earthquake Administration

The Ashikule volcanic cluster （AVC） in western Kunlun Mountains is located in a graben region at the convergence of the Altun and Kangxiwa fault zones,and consists of more than 10 main volcanoes and dozens of *** Ashi volcano lies in the central part of the volcanic *** lithology,chemical composition and texture of Ashi volcanic rocks were studied in detail,and their implication in magmatic processes was *** phenocrysts in Ashi volcanic rocks consist mainly of plagioclase and pyroxene,and the statistical results of phenocryst contents show that the rocks can be subdivided into two *** group A,the content of pyroxene phenocrysts is generally higher than that of plagioclase phenocrysts,but an inverse relation occurs in group *** TAS diagram,the compositions of both groups fall into the trachyandensite field,but they are obviously concentrated into two *** two clusters exist also in the oxide *** pyroxene phenocrysts comprise augite,bronzite and hypersthene,and their Mg# histogram shows two *** phenocrysts with reaction rim are observed in rocks of both *** An values of the core are generally 30-40,and those of the rim are 44-48,which are closer to those of euhedral *** bronzites are in equilibrium with the melt,and two sets of magma depths,i.e.,18-25 km and 13-18 km,can be estimated by using thermobarometer proposed by *** hypersthenes are not in equilibrium with the melt,and can be assigned to *** crystal size distribution （CSD） curves of plagioclase appear as kinked lines indicative of magma *** above analyses show that two magma pockets might exist beneath the Ashi *** is likely that they are connected with each *** one has more evolved and contains more acidic magma,and the other is a trachyandensite magma pocket characterized by *** magma from the upper part of the trachyandensite magma pocket might mix with more acidic magma,r

关键词： texture chemical composition crystal size distribution Ashi volcano Ashikule volcanic cluster

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Abnormal strain changes observed at Guza before the Wenchuan earthquake

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Science China Earth Sciences 2011年第2期54卷 233-240页

作者： QIU ZeHua ZHANG BaoHong CHI ShunLiang TANG Lei SONG Mo Institute of Crustal Dynamics China Earthquake Administration Beijing 100085 China Hebi Seismological Bureau Hebi 458000 China

An YRY-4 type borehole strainmeter at Guza station on the southwest end of the Longmenshan fault zone recorded anomalous changes from time to time since about one year before the Wenchuan *** anomaly is characterized by steps and/or asymmetrical pulses of short-periods(minutes-hours).Among about one hundred stations over the mainland of China,only Guza,the nearest one to the seismic area,observed such changes.A self-check function of the strainmeter helps confirm the credibility of the *** anomalous signals do not correspond to seasonal *** consistency in the sense of strain among long-term,anomalous interfering and coseismic changes suggests that they all resulted from the background tectonic *** of an Overrun Rate Analysis further illustrate a close temporal relevance of the anomaly to the Wenchuan earthquake:its increase before,and decrease after the biggest changes during the main *** abnormal changes are attributed to local small-scale fractures with an evidential clue that the only Ms4.5 foreshock near Guza station on February 27,2008 produced the biggest anomalous *** means of Wavelet Decomposition,it is revealed that longer period portion of the anomaly took place later before the main shock,consistent with the idea that scales of small fractures increase during earthquake preparation *** anomalous strain changes are analogous to the stress changes observed before the 1976 Tangshan earthquake.

关键词： Wenchuan earthquake earthquake precursor strain change 4-component borehole strainmeter Overrun-Rate-Analysis

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The strain seismograms of P- and S-waves of a local event recorded by four-gauge borehole strainmeter

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earthquake Science 2015年第3期28卷 209-214页

作者： Zehua Qiu Shunliang Chi Zhenming Wang Seth Carpenter Lei Tang Yanping Guo Guang Yang Institute of Crustal Dynamics China Earthquake Administration earthquake Administration of Hebi Kentucky Geological Survey University of Kentucky Guza Seismic Station Earthquake Administration of Sichuan Province

At a sampling rate of 100 samples per second,the YRY-4 four-gauge borehole strainmeters（FGBS） are capable of recording transient strains caused by seismic waves such as P and S waves or strain seismograms. At such a high sampling rate, data from the YRY-4 strainmeters demonstrate fairly satisfactory self-consistency. The strain tensor seismograms demonstrate the senses of motion of P waves, that is, the type of seismic wave travels in the direction of the maximum normal strain change. The observed strain patterns of S waves significantly differ from those of P waves and should contain information about the source mechanism. Spectrum analysis shows that the strain seismograms are consistent with conventional broadband seismograms from the same site.

关键词： Four-gauge borehole strainmeter(FGBS) Strain seismogram P-wave S-wave Self-consistency Spectrum analysis

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