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New Evidence of Late Quaternary Activity on the Xinyi-Wuhe Segment of the Tancheng-Lujiang Fault Zone

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earthquake research in China 2014年第3期28卷 311-319页

作者： Zheng Yingping Yao Daquan Zhang Yi Zhang Weijing Zhai Hongtao Zhao Peng Li Guang earthquake Administration of Anhui Province National earthquake Response Support Service CEA

The Tancheng-Lujiang fault zone has great influence in eastern China. Studies have shown obvious signs of neotectonic activities on the Xinyi-Wuhe segment of the Tancheng-Lujiang fault zone. In this study,on the basis of the previous work,many seismological surveys are made along the Tancheng-Lujiang fault zone and trenches are excavated in key *** with the analysis of the seismic activities along the fault,the fault movement features and future seismic risk are discussed. Much first-hand information obtained in the paper can provide an important reference value for the study of large earthquake recurrence rules and the mid and long-term earthquake prediction on the Xinyi-Wuhe segment of the Tancheng-Lujiang fault zone.

关键词： Tancheng-Lujiang fault zone Xinyi-Wuhe segment Late Quaternary Evidence of fault activity

Maars in the Xilinhot-Abaga Volcanic Cluster

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earthquake research in China 2013年第3期27卷 401-410页

作者： Wang Xijiao Bai Zhida Tan Lin Wu Zhili Wang Yan School of Earth Sciences and Resources China University of Geosciences Department of Land and Resources of Inner Mongolia Autonomous Region

Located in Xilin Gol League of Inner Mongolia Autonomous Region,the Xilinhot-Abaga volcanic cluster is in the centre of the Daxing’anling-Datong volcanic eruption *** than 300 Quaternary basaltic volcanoes of different types are developed in the volcanic eruption *** are found for the first time in the study area,with those in Haotewula in the southeast of Abagaqi,and Chelewula and Esigewula in the northwest of Abagaqi to be the most *** all are large in scale,with cone diameters generally 3~4km,with the largest up to *** maars show intact structure,a similar two-ringed mountain landscape and obviously phased eruption which contained a vigorous phreatomagmatic explosion at the earlier stage,and weak magmatic explosion at the later stage,and basaltic lava effusion in the last *** eruption sequence reflects the interaction between magma and water,the change of intrusive speed and outflow rate of *** Middle Pleistocene deposits of sand and gravel in the valley are covered by basal surge *** TL age of sandstone-shale 'xenolith'which was found in the spatter deposits close to the crater is( 0.112 ± 0.0096) Ma,indicating that the eruption time of the Maars was the early Late Pleistocene.

关键词： Phreatomagmatic explosion Base surge Maar, Xilinhot-Abaga volcanic cluster

Pulse-like ground motion observed during the 6 February 2023 M_(W)7.8 Pazarcık earthquake(Kahramanmaraş,SE Türkiye)

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地震学报:英文版 2023年第4期36卷 328-339页

作者： Fan Wu Junju Xie Zhao An Chenghao Lyu Tuncay Taymaz Tahir Serkan Irmak Xiaojun Li Zengping Wen Baofeng Zhou Institute of Geophysics China Earthquake AdministrationBeijing 100081China School of Earth and Space Sciences Peking UniversityBeijing 100871China Department of Geophysical Engineering The Faculty of Minesİstanbul Technical UniversityMaslak 34467SarıyerİstanbulTürkiye Department of Geophysical Engineering Kocaeli UniversityUmuttepe 41380KocaeliTürkiye College of Architecture and Civil Engineering Beijing University of TechnologyBeijing 100124China Institute of Engineering Mechanics China Earthquake AdministrationHarbin 150080China

In this study,we analyzed 100 three-component strong ground motion records observed within 200 km of the causative fault of the 6 February 2023 M_(W)7.8 Pazarcık(Kahramanmaraş)earthquake in SE Tü*** wavelet method was utilized to identify and analyze the characteristics of pulse-like ground motions in the near-fault region,while considering the uncertainty of the pulse orientation during the *** investigation focused on the effects of the focal mechanism and rupture process on the spatial distribution,pulse orientation,and maximum pulse direction of the observed pulse-like ground *** also analyzed the amplitude and period of the observed ground pulses and the effect of long-period amplification on the ground motion response *** results indicated the following:(1)A total of 21 typical ground velocity pulses were observed during this earthquake,exhibiting complex characteristics due to the influence of the strike-slip mechanism and rupture *** ground pulses(17 out of 21)were recorded within 20 km of the fault,in a wide range of orientations,including normal and parallel to the fault *** waveforms exhibited unidirectional features,indicating the effects of left-lateral fault *** pulses observed more than 20 km from the fault were mainly oriented normal to the *** waveforms were bidirectional with double-or multi-round trips as a result of rupture directivity.(2)The amplitudes of the observed pulses ranged from 30.5 to 220.0 cm/s,with the largest peak velocity of 220.0 cm/s observed at Station *** pulse periods ranged from 2.3 to 14.5 s,with the longest pulse period of 14.5 s observed at Station *** amplitude and period of the pulses observed during this earthquake were comparable to those of similar-magnitude global *** amplitude of the pulses decreased significantly with increasing fault distance,whereas the pulse period was not significantly affected by the fault distance.(3)Com

关键词： 2023 M_(W)7.8 Pazarcık earthquake pulse-like ground motion response spectrum predominant period

High-precision relocation of the aftershock sequence of the January 8,2022,M_(S)6.9 Menyuan earthquake

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earthquake Science 2022年第2期35卷 138-145页

作者： Liping Fan Boren Li Shirong Liao Ce Jiang Lihua Fang Institute of Geophysics China Earthquake AdministrationBeijing 100081China Guangdong earthquake Agency Guangzhou 510405China Fujian earthquake Agency Fuzhou 350003China Key Laboratory of earthquake Source Physics China Earthquake AdministrationBeijing 100081China

The 2022 Menyuan M_(S)6.9 earthquake,which occurred on January 8,is the most destructive earthquake to occur near the Lenglongling(LLL)fault since the 2016 Menyuan M_(S)6.4 *** relocated the mainshock and aftershocks with phase arrival time observations for three days after the mainshock from the Qinghai Seismic Network using the double-difference *** total length and width of the aftershock sequence are approximately 32 km and 5 km,respectively,and the aftershocks are mainly concentrated at a depth of 7-12 *** relocated sequence can be divided into 18 km west and 13 km east segments with a boundary approximately 5 km east of the mainshock,where aftershocks are *** east and west fault structures revealed by aftershock locations differ *** west fault strikes EW and inclines to the south at a 71°-90°angle,whereas the east fault strikes 133°and has a smaller dip *** strain accumulates at conjunctions of faults with different slip rates where it is prone to large *** on surface traces of faults,the distribution of relocated earthquake sequence and surface ruptures,the mainshock was determined to have occurred at the conjunction of the Tuolaishan(TLS)fault and LLL fault,and the west and east segments of the aftershock sequence were on the TLS fault and LLL fault,*** migrate in the early and late stages of the earthquake *** the first 1.5 h after the mainshock,aftershocks expand westward from the *** the late stage,seismicity on the northeast side of the east fault is higher than that in other *** migration rate of the west segment of the aftershock sequence is approximately 4.5 km/decade and the afterslip may exist in the source region.

关键词： Menyuan earthquake aftershock sequence double-difference relocation Lenglongling fault Tuolaishan fault

Spatial and Temporal Variations of Daily Ranges of the Geomagnetic Vertical Component in the Chinese Mainland

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earthquake research in China 2013年第1期27卷 91-100页

作者： Li Junhui Li Qi Wang Xingzhou He Kang Tao Yuechao Chen Jun earthquake Administration of Anhui Province National Geophysical Observatory at Mengcheng Institutes of Geophysics CEA

In this paper, we use the daily ranges of the vertical magnetic intensity of approximately 76 geomagnetic stations from January 1, 2008 to December 31, 2010 to analyze the spatial and temporal characteristics of Z ranges. The results are summarized as follows: (1) Temporally, we use regressive analysis and FFT analysis to analyze the data. The results show that the Z component daily ranges of all stations have an obvious cyclical variation, the computed Fourier spectra of all data sets have clearly resolved the required periodicities in the data, in the form of distinct peaks at days 365, 183, 22, and 73, and the power spectra of day 365 is the highest in all periods. (2) In terms of spatial variation, the daily ranges show nonlinear variation with latitude in China. The results show the existence of a point of inflexion (maximal value point) nearby at about 25°N, the daily ranges of Z rise from 15°~25°N and have a good linear decrease variation along with 25°~50°N. (3) Compared with the spatial and temporal variations of Z daily ranges with the Sq current inversion, we found that the spatial and temporal characteristics of Z ranges are decided mainly by the spatio-temporal evolution of the Sq current system. (4) If the latitudes of the maximum amplitudes of variation of the vertical component in the geomagnetic quiet days are roughly taken as the latitudes corresponding to the foci of Sq overhead current system, we can see that these latitudes of foci become higher in summer, are lowest in winter and highest during Equinoxes, displaying conspicuous monthly and daily variations. For two successive geomagnetic quiet days, the latitudes of foci may vary ten degrees.

关键词： Chinese mainland Geomagnetic Daily ranges of Z component Spatial and temporal variations

Analysis on b-value Abnormality of the Minxian-Zhangxian,Gansu M_S6.6 earthquake

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earthquake research in China 2016年第2期30卷 186-192页

作者： Feng Jiangang Zhang Hui Yang Ping Lanzhou Institute of Seismology China Earthquake AdministrationLanzhou 730000China earthquake Administration of Xinjiang Uygur Autonomous Region Ummqi 830011China

In this paper,based on Gansu Digital Seismic Network data since 1990,we calculated b-value and ⊿ b-value of the neighborhood area before the 2013 Minxian-Zhangxian M_S6. 6,earthquake. The results show that the earthquake occurred at the margin of the significantly lower b-value area in southeast of Gansu and before the earthquake the neighborhood area had an obviously abnormal ⊿ b-value. From the earthquake and the spatial distribution of low b-value, the region still has the possibility of generating dangerous strong earthquakes.

关键词： Minxian-Zhangxian earthquake b-value Southeastern Gansu

3D v_P and v_S models of southeastern margin of the Tibetan plateau from joint inversion of body-wave arrival times and surface-wave dispersion data

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earthquake Science 2017年第1期30卷 17-32页

作者： Lina Gao Haijiang Zhang Huajian Yao Hui Huang School of Geoexploration Science and Technology Jilin University Laboratory of Seismology and Physics of Earth’s Interior School of Earth and Space SciencesUniversity of Science and Technology of China National Geophysical Observatory at Mengcheng Department of Earth Atmospheric and Planetary SciencesMassachusetts Institute of Technology

A new 3D velocity model of the crust and upper mantle in the southeastern （SE） margin of the Tibetan plateau was obtained by joint inversion of body- and sur- face-wave data. For the body-wave data, we used 7190 events recorded by 102 stations in the SE margin of the Tibetan plateau. The surface-wave data consist of Rayleigh wave phase velocity dispersion curves obtained from ambient noise cross-correlation analysis recorded by a dense array in the SE margin of the Tibetan plateau. The joint inversion clearly improves the Vs model because it is constrained by both data types. The results show that at around 10 km depth there are two low-velocity anomalies embedded within three high-velocity bodies along the Longmenshan fault system. These high-velocity bodies correspond well with the Precambrian massifs, and the two located to the northeast of 2013 Ms 7.0 Lushan earthquake are associated with high fault slip areas during the 2008 Wenchuan earthquake. The aftershock gap between 2013 Lushan earthquake and 2008 Wenchuan earthquake is associated with low-velocity anomalies, which also acts as a barrier zone for ruptures of two earthquakes. Generally large earthquakes （M 〉 5） in the region occurring from 2008 to 2015 are located around the high-velocity zones, indicating that they may act as asperities for these large earthquakes. Joint inversion results also clearly show that there exist low-velocity or weak zones in the mid-lower crust, which are not evenly distributed beneath the SE margin of Tibetan plateau.

关键词： Joint inversion - Body waves Surface waves Aftershock gap The southeastern margin of Tibetan plateau

Active faults and seismogenic models for the Urumqi city,Xinjiang Autonomous Region, China

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earthquake Science 2016年第3期29卷 173-184页

作者： Yingzhen Li Yang Yu Jun Shen Bo Shao Gao Qi Mei Deng Institute of Disaster Prevention

We have studied the characteristics of the active faults and seismicity in the vicinity of Urumqi city, the capital of Xinjiang Autonomous Region, China, and have proposed a seismogenic model for the assessment of earthquake hazard in this area. Our work is based on an integrated analysis of data from investigations of active faults at the surface, deep seismic reflection soundings, seismic profiles from petroleum exploration, observations of temporal seismic stations, and the precise location of small earthquakes. We have made a comparative study of typical seismogenic structures in the frontal area of the North Tianshan Mountains, where Urumqi city is situated, and have revealed the primary features of the thrust-fold- nappe structure there. We suggest that Urumqi city is comprised two zones of seismotectonics which are inter- preted as thrust-nappe structures. The first is the thrust nappe of the North Tianshan Mountains in the west, con- sisting of the lower （root） thrust fault, middle detachment, and upper fold-uplift at the front. Faults active in the Pleistocene are present in the lower and upper parts of this structure, and the detachment in the middle spreads toward the north. In the future, M7 earthquakes may occur at the root thrust fault, while the seismic risk of frontal fold-uplift at the front will not exceed M6.5. The second structure is the western flank of the arc-like Bogda nappe in the east, which is also comprised a root thrust fault, middle detachment, and upper fold-uplift at the front, of which the nappe stretches toward the north; several active faults are also developed in it. The fault active in the Holocene is called the South Fukang fault. It is not in the urban area of Urumqi city. The other three faults are located in the urban area and were active in the late Pleistocene. In these cases, this section of the nappe structure near the city has an earthquake risk of M6.5-7, An earthquake Ms6.6, 60 km east to Urumqi city occurred along the

关键词： Urumqi Active fault Seismogenic structure Thrust Nappe

Temporal vP/vS variation characteristics in different zones of China's Capital Circle area before and after Wen'an earthquake

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Acta Seismologica Sinica(English Edition) 2008年第3期21卷 243-257页

作者：王林瑛郭永霞刘芳蒋长胜 Institute of Geophysics China Earthquake Administration earthquake Administration of Inner Mongolia Autonomous Region

On July 4, 2006, an earthquake of MS5.1 took place in Wen’an, Hebei Province, just at the south center of China’s Capital Circle area digital seismograph network. It is the strongest event recorded ever since the network went into operation in 2002. We processed the vast amounts of phase data yielded by the 107 digital seismic stations between 2002~2007 using Wadati method. In order to improve the precision and stability of shear and compressional wave velocities (vP/vS) calculation, we impose a number of restrictions on the computation environment and condition, e.g., the earthquakes are densely concentrated, selected stations are limited in range, the number of stations in- volved in the computation is larger than 5 and linear fitting features high precision and small error. Under these restrictions, the study shows that vP/vS in and around Wen’an and Tangshan underwent a normal-low-normal proc- ess one year before Wen’an earthquake, vP/vS became obviously low and the low ratio lasted for about one year, meanwhile, little variation of vP/vS was seen in Xingtai, northwest of Beijing, southwest of Beijing, Beijing-Tianjin and Beijing; after the quake, the vP/vS returned normal in Wen’an and Tangshan. Error and stability analysis of the calculated result for vP/vS shows it is convincible that anomaly appeared in and around Wen’an and Tangshan be- fore Wen’an earthquake.

关键词： Wen’an earthquake ratio of shear and compressional wave velocities earthquake prediction