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Deep tectonics and seismogenic mechanisms of the seismic source zone of the Jishishan M_(s)6.2 earthquake on December 18,2023,at the northeast margin of the Tibetan Plateau

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Earth and Planetary Physics 2024年第3期8卷 514-521页

作者： Qiong Wang ShuYu Li XinYi Li Yue Wu PanPan Zhao Yuan Gao Key Laboratory of Earthquake Prediction Institute of Earthquake ForecastingChina Earthquake AdministrationBeijing 100036China institute of Geophysics China Earthquake AdministrationBeijing 100081China

On December 18,2023,an M_(s)6.2 earthquake occurred in Jishishan,Gansu Province,*** earthquake happened in the eastern region of the Qilian Orogenic Belt,which is situated at the forefront of the NE margin of the Tibetan Plateau(i.e.,Qinghai-Tibet Plateau),encompassing a rhombic-shaped area that intersects the Qilian-Qaidam Basin,Alxa Block,Ordos Block,and South China *** this study,we analyzed the deep tectonic pattern of the Jishishan earthquake by incorporating data on the crustal thickness,velocity structure,global navigation satellite system(GNSS)strain field,and *** discovered that the location of the earthquake was related to changes in the crustal *** results showed that the Jishishan M_(s)6.2 earthquake occurred in a unique position,with rapid changes in the crustal thickness,Vp/Vs,phase velocity,and S-wave *** epicenter of the earthquake was situated at the transition zone between high and low velocities and was in proximity to a low-velocity ***,the source area is flanked by two high-velocity anomalies from the east and *** principal compressive strain orientation near the Lajishan Fault is primarily in the NNE and NE directions,which align with the principal compressive stress direction in this *** some areas of the Lajishan Fault,the principal compressive strain orientations show the NNW direction,consistent with the direction of the upper crustal fast-wave polarization from local earthquakes and the phase velocity azimuthal *** features underscore the relationship between the occurrence of the Jishishan M_(s)6.2 earthquake and the deep inhomogeneous structure and deep tectonic *** NE margin of the Tibetan Plateau was thickened by crustal extension in the process of northeastward expansion,and the middle and lower crustal materials underwent structural deformation and may have been filled with salt-containing fluids during the extension *** presence

关键词： Jishishan M_(s)6.2 earthquake crustal structure anisotropy stress and strain seismogenic mechanism northeast margin of the Tibetan Plateau

The Contribution of United States Aircraft Reconnaissance Data to the China Meteorological administration Tropical Cyclone Intensity Data:An Evaluation of Homogeneity

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Advances in Atmospheric Sciences 2024年第4期41卷 639-654页

作者： Ming YING Xiaoqin LU Shanghai Typhoon institute China Meteorological AdministrationShanghai 200030China

This paper investigates the homogeneity of United States aircraft reconnaissance data and the impact of these data on the homogeneity of the tropical cyclone(TC)best track data for the seasons 1949-1987 generated by the China Meteorological administration(CMA).The evaluation of the reconnaissance data shows that the minimum central sea level pressure(MCP)data are relatively homogeneous,whereas the maximum sustained wind(MSW)data show both overestimations and spurious abrupt *** comparisons suggest that both the reconnaissance MCP and MSW were well incorporated into the CMA TC best track *** no spurious abrupt changes were evident in the reconnaissance-related best track MCP data,two spurious changepoints were identified in the remainder of the best-track MCP ***,the influence of the reconnaissance MSWs seems to extend to the best track MSWs unrelated to reconnaissance,which might reflect the optimistic confidence in making higher estimates due to the overestimated extreme wind“observations”.In addition,the overestimation of either the reconnaissance MSWs or the best track MSWs was greater during the early decades compared to later decades,which reflects the important influence of reconnaissance data on the CMA TC best track *** wind-pressure relationship(WPR)used in the CMA TC best track dataset is also evaluated and is found to overestimate the MSW,which may lead to inhomogeneity within the dataset between the aircraft reconnaissance era and the satellite era.

关键词： tropical cyclone intensity homogeneity best track aircraft reconnaissance

A redundant subspace weighting procedure for clock ensemble

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Chinese Physics B 2024年第4期33卷 435-442页

作者：徐海陈煜刘默驰王玉琢 National institute of Metrology Beijing 100029China Key Laboratory of State administration for Market Regulation Beijing 100029China China National Intellectual Property administration Beijing 100088China

A redundant-subspace-weighting(RSW)-based approach is proposed to enhance the frequency stability on a time scale of a clock *** this method,multiple overlapping subspaces are constructed in the clock ensemble,and the weight of each clock in this ensemble is defined by using the spatial covariance *** superimposition average of covariances in different subspaces reduces the correlations between clocks in the same laboratory to some *** optimizing the parameters of this weighting procedure,the frequency stabilities of virtual clock ensembles are significantly improved in most cases.

关键词： weighting method redundant subspace clock ensemble time scale

Tropical Cyclone Monitoring and Analysis Techniques: A Review

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Journal of Meteorological Research 2024年第2期38卷 351-367页

作者： Chuanhai QIAN Ying LI Yinglong XU Xin WANG Zenghai ZHANG Gaozhen NIE Da LIU Shiwen ZHANG institute for Development and Programme Design China Meteorological AdministrationBeijing 100081 Chinese Academy of Meteorological Sciences China Meteorological AdministrationBeijing 100081 National Meteorological Centre China Meteorological AdministrationBeijing 100081 National Satellite Meteorological Centre China Meteorological AdministrationBeijing 100081

Tropical cyclones(TCs),including tropical depressions and different categories of typhoons,hurricanes,and cyclonic storms,mostly originate over the oceans in the absence of direct ***,detailed monitoring and analysis of TCs has always been an unsolved *** the recent 20 years,great changes have taken place in domestic and foreign TC monitoring techniques,imposing a significant impact on TC operations and *** new technologies and products gradually emerge to support operations,with improved monitoring *** this paper,the progress on TC monitoring and analysis via meteorological satellites,radars,and airplanes in China and the world is reviewed,compared,and summarized,with special focuses on multisatellite fusion observations,in situ aircraft measurements,and some unconventional observation equipment such as rockets,saildrones,and underwater *** this basis,the paper points out future directions for improving TC monitoring and analysis in aid of better TC forecast and early warning.

关键词： tropical cyclone(TC) monitoring and analysis meteorological satellite aircraft reconnaissance

Earthquake potential across the North–South seismic belt of China

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Science Bulletin 2024年第2期69卷 179-182页

作者： Yanchuan Li Xinjian Shan Chunyan Qu Guohong Zhang Xiaogang Song State Key Laboratory of Earthquake Dynamics Institute of GeologyChina Earthquake AdministrationBeijing 100029China

The elastic rebound theory,which frames our understanding of earthquakes,suggests that the accumulated elastic strain on faults will ultimately be released through earthquakes[1].As such,identifying the location,rate,and accumulation of slip deficit on faults constitutes a basis for seismic potential assessment[2].Interseismic coupling(ISC)refers to the ratio of the slip deficit rate on a fault to the far-field loading rate,where full and no coupling correspond to 100%and 0%slip deficits,respectively.

关键词： seismic belt fault

Analysis of faulting destruction and water supply pipeline damage from the first mainshock of the February 6,2023 Türkiye earthquake doublet

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Earthquake Science 2024年第1期37卷 78-90页

作者： Xiaoqing Fan Libao Zhang Juke Wang Yefei Ren Aiwen Liu institute of Geophysics China Earthquake AdministrationBeijing 100081China institute of Engineering Mechanics China Earthquake AdministrationHarbin 150080China

In 2023,two consecutive earthquakes exceeding a magnitude of 7 occurred in Türkiye,causing severe casualties and economic *** damage to critical urban infrastructure and building structures,including highways,railroads,and water supply pipelines,was particularly severe in areas where these structures intersected the seismogenic *** infrastructure projects that traverse active faults are susceptible to the influence of fault movement,pulse velocity,and ground *** this study,we used a unique approach to analyze the acceleration records obtained from the seismic station array(9 strong ground motion stations)located along the East Anatolian Fault(the seismogenic fault of the MW7.8 mainshock of the 2023 Türkiye earthquake doublet).The acceleration records were filtered and integrated to obtain the velocity and displacement time *** used the results of an on-site investigation,jointly conducted by China Earthquake administration and Türkiye’s AFAD,to analyze the distribution of PGA,PGV,and PGD recorded by the strong motion array of the East Anatolian *** found that the maximum horizontal PGA in this earthquake was 3.0 g,and the maximum co-seismic surface displacement caused by the East Anatolian Fault rupture was 6.50 *** the fault rupture propagated southwest,the velocity pulse caused by the directional effect of the rupture increased gradually,with the maximum PGA reaching 162.3 cm/*** also discussed the seismic safety of critical infrastructure projects traversing active faults,using two case studies of water supply pipelines in Türkiye that were damaged by *** used a three-dimensional finite element model of the PE(polyethylene)water pipeline at the Islahiye State Hospital and fault displacement observations obtained through on-site investigation to analyze pipeline failure *** further investigated the effect of the fault-crossing angle on seismic safety of a pipeline,based on our analysis and the failure p

关键词： Türkiye earthquake fault displacement near-fault ground motion velocity pulse water supply pipeline

On the eigenvalues and eigendisplacement of the critical mode in horizontally layered media

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Earthquake Science 2024年第1期37卷 13-35页

作者： Shaotong Wang Laiyu Lu The institute of Geophysics China Earthquake AdministrationBeijing 100081China

Wave propagation in horizontally layered media is a classical problem in seismic-wave *** semi-infinite space,a nondispersive Rayleigh wave mode exists,and the eigendisplacement decays exponentially with *** a layered model with increasing layer velocity,the phase velocity of the Rayleigh wave varies between the S-wave velocity of the bottom half-space and that of the classical Rayleigh wave propagated in a supposed half-space formed by the parameters of the top *** the phase velocity is the same as the P-or S-wave velocity of the layer,which is called the critical mode or critical phase velocity of surface waves,the general solution of the wave equation is not a homogeneous(expressed by trigonometric functions)or inhomogeneous(expressed by exponential functions)plane wave,but one whose amplitude changes linearly with depth(expressed by a linear function).Theories based on a general solution containing only trigonometric or exponential functions do not apply to the critical mode,owing to the singularity at the critical phase *** this study,based on the classical framework of generalized reflection and transmission coefficients,the propagation of surface waves in horizontally layered media was studied by introducing a solution for the linear function at the critical phase ***,the eigenvalues and eigenfunctions of the critical mode can be calculated by solving a singular *** eigendisplacement characteristics associated with the critical phase velocity were investigated for different layered *** contrast to the normal mode,the eigendisplacement associated with the critical phase velocity exhibits different *** the phase velocity is equal to the S-wave velocity in the bottom half-space,the eigendisplacement remains constant with increasing depth.

关键词： dispersion curve eigenvalue generalized reflection and transmission coefficient surface wave guide wave

Variations of shear-wave splitting parameters in the source region of the 2023 Türkiye doublet earthquakes

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Earthquake Science 2024年第2期37卷 174-187页

作者： Xuelai Cao Lijun Chang institute of Geophysics China Earthquake AdministrationBeijing 100081China

In this study,the shear-wave splitting parameters of local seismic events from the source regions of the 2023 Türkiye MW7.7 and MW7.6 doublet earthquakes(event 1 and event 2,respectively)were measured from June 1,2022,to April 25,2023,and their spatiotemporal characteristics were *** results revealed clear spatial and temporal ***,the dominant fast-wave polarization direction at each station shows a strong correlation with the direction of the maximum horizontal principal compressive stress,as characterized by focal mechanism solutions of seismic events(MW≥3.5)near the *** dominant fast-wave polarization direction and the regional stress field also showed a strong correlation with the intermovement of the Arabian Plate,African Plate,and Anatolian *** the Nurdagi-Pazarcik fault zone,the seismic fault of event 1,stations closer to the middle of the fault where the mainshock occurred exhibited notably greater delay times than stations located towards the ends of the fault and far from the *** addition,the stations located to the east of the Nurdagi-Pazarcik fault and to the north of the Sürgüfault also exhibited large delay *** spatial distribution of shear-wave splitting parameters obtained from each station indicates that the upper-crust anisotropy in the source area is mainly controlled by the regional stress field,which is closely related to the state of the block *** the seismogenic process of the MW7.7 earthquake,more stress accumulated in the middle of the Nurdagi-Pazarcik fault than at either end of the *** the influence of the MW7.7 and MW7.6 events,the stress that accumulated during the seismogenic process of the earthquake doublet may have migrated towards some areas outside the aftershock intensive area after the earthquakes,and the crustal stress and its adjustment range near the outer stations increased *** the exception of two stations with few effective events,all

关键词： Türkiye doublet earthquakes shear-wave splitting upper crustal anisotropy stress field

The MW5.5 earthquake on August 6,2023,in Pingyuan,Shandong,China:A rupture on a buried fault

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Earthquake Science 2024年第1期37卷 1-12页

作者： Zhe Zhang Lisheng Xu Lihua Fang institute of Geophysics China Earthquake AdministrationBeijing 100081China

On August 6,2023,a magnitude MW5.5 earthquake struck Pingyuan County,Dezhou City,Shandong Province,*** event was significant as no large earthquakes had been recorded in the region for over a century,and no active fault had been previously *** study collects 1309 P-wave arrival times and 866 S-wave arrival times from 74 seismic stations less than 200 km to the epicenter to constrain the spatial distribution of the mainshock and its 125 early aftershocks by the double difference earthquake relocation method,and selects 864 P-waveforms from 288 stations located within 800 km of the epicenter to constrain the focal mechanism solution of the mainshock through centroid moment tensor *** relocation and the inversion indicate,the Pingyuan MW5.5 earthquake was caused by a rupture on a buried fault,likely an extensive segment of the Gaotang *** buried fault exhibited a dip of approximately 75°to the northwest,with a strike of 222°,similar to the Gaotang *** rupture initiated at the depth of 18.6 km and propagated upward and ***,the ground surface was not *** total duration of the rupture was~6.0 s,releasing the scalar moment of 2.5895×1017 N·m,equivalent to *** moment rate reached the maximum only 1.4 seconds after the rupture initiation,and the 90%scalar moment was released in the first 4.6 *** the first 1.4 seconds of the rupture process,the rupture velocity was estimated to be 2.6 km/s,slower than the local S-wave *** the rupture neared its end,the rupture velocity decreased *** study provides valuable insights into the seismic characteristics of the Pingyuan MW5.5 earthquake,shedding light on the previously unidentified buried fault responsible for the seismic activity in the *** the behavior of such faults is crucial for assessing seismic hazards and enhancing earthquake preparedness in the future.

关键词： Shandong Pingyuan MW5.5 earthquake double-difference earthquake location centroid moment tensor inversion buried fault