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Estimation of free core nutation parameters and availability of computing options

Geodesy and Geodynamics 2024年第1期15卷 61-74页

作者： Weiwei Yang Xiaoming Cui jianqiao xu Qingchao Liu Ming Qin State Key Laboratory of Geodesy and Earth's Dynamics Innovation Academy for Precision Measurement Science and TechnologyChinese Academy of SciencesWuhan 430077China University of Chinese Academy of Sciences Beijing 100049China Hubei Luojia Laboratory Wuhan 430079China

The Earth’s Free Core Nutation(FCN) causes Earth tides and forced nutation with frequencies close to the FCN that exhibit resonance effects.High-precision superconducting gravimeter(SG) and very long baseline interferometry(VLBI) provide good observation techniques for detecting the FCN parameters.However,some choices in data processing and solution procedures increase the uncertainty of the FCN parameters.In this study,we analyzed the differences and the effectiveness of weight function and ocean tide corrections in the FCN parameter detection using synthetic data,SG data from thirty-one stations,and the 10 celestial pole offset(CPO) series.The results show that significant discrepancies are caused by different computing options for a single SG station.The stacking method,which results in a variation of0.24-5 sidereal days(SDs) in the FCN period(T) and 10^(3)-10^(4) in the quality factor(Q) due to the selection of the weighting function and the ocean tide model(OTM),can effectively suppress this influence.The statistical analysis results of synthetic data shows that although different weight choices,while adjusting the proportion of diurnal tidal waves involved,do not significantly improve the accuracy of fitted FCN parameters from gravity observations.The study evaluated a series of OTMs using the loading correction efficiency.The fitting of FCN parameters can be improved by selecting the mean of appropriate OTMs based on the evaluation results.Through the estimation of the FCN parameters based on the forced nutation,it was found that the weight function P_(1) is more suitable than others,and different CPO series(after 2009) resulted in a difference of 0.4 SDs in the T and of 103 in the Q.We estimated the FCN parameters for SG(T=430.4±1.5 SDs and Q=1.52×10^(4)±2.5×10^(3)) and for VLBI(T=429.8±0.7 SDs,Q=1.88×10^(4)±2.1×10^(3)).

关键词： Free core nutation Superconducting gravimeter Very long baseline interferometry Weight function Ocean tide model

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Probing signals of atmospheric gravity waves excited by the July 29,2021 M_(W)8.2 Alaska earthquake

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Geodesy and Geodynamics 2024年第3期15卷 219-229页

作者： Geng Zhang jianqiao xu Xiaodong Chen Heping Sun Lizhuo Gong State Key Laboratory of Geodesy and Earth's Dynamics Innovation Academy for Precision Measurement Science and TechnologyChinese Academy of SciencesWuhan430077China University of Chinese Academy of Sciences Beijing100049China

It is commonly believed that the atmosphere is decoupled from the solid Earth.Thus,it is difficult for the seismic wave energy inside the Earth to propagate into the atmosphere,and atmospheric pressure wave signals excited by earthquakes are unlikely to exist in atmospheric observations.An increasing number of studies have shown that earthquakes,volcanoes,and tsunamis can perturb the Earth's atmosphere due to various coupling effects.However,the observations mainly focus on acoustic waves with periods of less than 10 min and inertial gravity waves with periods of greater than 1 h.There are almost no clear observations of gravity waves that coincide with observations of low-frequency signals of the Earth's free oscillation frequency band within 1 h.This paper investigates atmospheric gravity wave signals within1 h of surface-atmosphere observations using the periodogram method based on seismometer and microbarometer observations from the global seismic network before and after the July 29,2021 M_(w)8.2 Alaska earthquake in the United States.The numerical results show that the atmospheric gravity wave signals with frequencies similar to those of the Earth's free oscillations _(0)S_(2) and _(0)T_(2) can be detected in the microbaro meter observations.The results con firm the existence of atmospheric gravity waves,indicating that the atmosphere and the solid Earth are not decoupled within this frequency band and that seismic wave energy excited by earthquakes can propagate from the interior of the Earth to the atmosphere and enhance the atmospheric gravity wave signals within 1 h.

关键词： Atmospheric gravity modes Atmospheric gravity waves Alaska earthquake Normal modes Coupling of solid earth and atmosphere

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Rapid rupture characterization for the 2023 M_(S)6.2 Jishishan earthquake

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Earthquake Research Advances 2024年第2期4卷 22-26页

作者： Xiongwei Tang Rumeng Guo Yijun Zhang Kun Dai jianqiao xu Jiangcun Zhou Mingqiang Hou Heping Sun State Key Laboratory of Geodesy and Earth's Dynamic Innovation Academy for Precision Measurement Science and TechnologyChinese Academy of SciencesWuhan430077China College of Earth and Planetary Sciences University of Chinese Academy of SciencesBeijing100101China Hubei Luojia Laboratory Wuhan430079China

On December 18, 2023, the M_(S)6.2 Jishishan earthquake occurred in the northeastern region of the QinghaiXizang Plateau, causing heavy casualties and property damage in Gansu and Qinghai Provinces. In this study,we integrate space imaging geodesy, finite fault inversion, and back-projection methods to decipher its rupture property, including fault geometry, coseismic slip distribution, rupture direction, and propagation speed. The results reveal that the seismogenic fault dips to the southwest at an angle of 29°. The major slip asperity is dominated by reverse slip and is concentrated within a depth range of 7–16 km, which explains the significant uplift near the epicenter observed by both the Sentinel-1 ascending and descending In SAR data. Moreover, the teleseismic array waveforms indicate a northwest propagating rupture with an overall slow rupture velocity of~1.91 km/s(AK array) or 1.01 km/s(AU array).

关键词： Jishishan earthquake Rupture property Space imaging geodesy Finite fault inversion Back-projection method

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Source characteristics of the mainshock and aftershocks of the 2019 Changning earthquake sequence:Implications for fluid effects

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Science China Earth Sciences 2023年第6期66卷 1321-1333页

作者： Kun DAI Yong ZHENG Rumeng GUO jianqiao xu School of Physics Huazhong University of Science and TechnologyWuhan 430074China Innovation Academy for Precision Measurement Science and Technology Chinese Academy of SciencesWuhan 430071China State Key Laboratory of Geological Processes and Mineral Resources School of Geophysics and GeomaticsChina University of GeosciencesWuhan 430074China

The 2019 M_(S)6.0 Changning earthquake occurred in the tectonically stable Sichuan Basin,where the epicenter and its adjacent areas are important shale gas and salt mine production fields,resulting in hot debates on whether the seismogenic mechanism of the 2019 Changning earthquake is related to human activities.As source characteristics and fluid pressure can provide important constraints on whether an earthquake is induced,weinvestigate the seismogenic mechanisms of the mainshock and 9 MW≥4.0 aftershocks.In overall,the mainshock and the majority of the aftershocks are characterized by relatively shallow focal depths(1‒4 km)and significant non-double-couple(non-DC)components.However,the mainshock and the aftershocks differ in two aspects:(1)the compensated-linear-vector-dipole components dominate the non-DC components of the mainshock,whereas the isotropic components dominate the most aftershocks;(2)the fluid overpressure of the mainshock is over 30 MPa,whereas the fluid overpressure of the most aftershocks is less than 10 MPa.Thus,we propose that the mainshock is triggered by weakened fault strength with long-term fluid injection,and that its large non-DC components are associated withcomplex rupture processes.Comparatively,the aftershocks may be triggered by postseismic stress transfer by combining the Coulomb failure stress changes in the poroelastic medium.Our results highlight the possible role of fluid in the occurrence of the Changning earthquake sequence.

关键词： The 2019 Channing earthquake Induced earthquakes Non-double-couple components Focal depths Poroelasticity

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Advances in immune response to pulmonary infection:Nonspecificity,specificity and memory

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Chronic Diseases and Translational Medicine 2023年第2期9卷 71-81页

作者： jianqiao xu Lixin Xie College of Pulmonary&Critical Care Medicine 8th Medical CenterChinese PLA General HospitalBeijingChina Medical School of Chinese PLA BeijingChina

The lung immune response consists of various cells involved in both innate and adaptive immune processes.Innate immunity participates in immune resistance in a nonspecific manner,whereas adaptive immunity effectively eliminates pathogens through specific recognition.It was previously believed that adaptive immune memory plays a leading role during secondary infections;however,innate immunity is also involved in immune memory.Trained immunity refers to the long-term functional reprogramming of innate immune cells caused by the first infection,which alters the immune response during the second challenge.Tissue resilience limits the tissue damage caused by infection by controlling excessive inflammation and promoting tissue repair.In this review,we summarize the impact of host immunity on the pathophysiological processes of pulmonary infections and discuss the latest progress in this regard.In addition to the factors influencing pathogenic microorganisms,we emphasize the importance of the host response.

关键词： adaptive immunity innate immunity lung infection trained immunity

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A review of tidal triggering of global earthquakes

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Geodesy and Geodynamics 2023年第1期14卷 35-42页

作者： Ruyu Yan Xiaodong Chen Heping Sun jianqiao xu Jiangcun Zhou State Key Laboratory of Geodesy and Earth's Dynamics Innovation Academy for Precision Measurement Science and TechnologyChinese Academy of SciencesWuhan 430077China University of Chinese Academy of Sciences Beijing 100049China

Earthquake prediction remains a challenging and difficult task for scientists all over the world.The tidal triggering of earthquakes is being proven by an increasing number of investigations,most of which have shown that earthquakes are positively correlated with tides,and thus,tides provide a potential tool for earthquake prediction,especially for imminent earthquakes.In this study,publications concerning the tidal triggering of earthquakes were compiled and analyzed with regard to global earthquakes,which were classified into three main types:tectonic,volcanic,and slow earthquakes.The results reveal a high correlation between tectonic earthquakes and tides(mainly for semidiurnal and diurnal tides;14-day tides) before and after the occurrence of significant earthquakes.For volcanic earthquakes,observations of volcanoes on the seafloor and land indicate that volcanic earthquakes in near-shore volcanic areas and mid-ocean ridges have a strong correlation with tidal forces,mostly those with semidiurnal and diurnal periods.For slow earthquakes,the periodicity of the tremor duration is highly correlated with semidiurnal and diurnal tides.In conclusion,the tidal triggering of these three types of earthquakes makes a positive contribution to earthquake preparation and understanding the triggering mechanism,and thus,the prediction of these types of earthquakes should be investigated.However,there are still several inadequacies on this topic that need to be resolved to gain a definitiveanswer regarding the tidal triggering of all earthquakes.The main inadequacies are discussed in this paper from our point of view.

关键词： Tidal triggering Tectonic earthquakes Volcanic earthquakes Slow earthquakes Earthquake prediction

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Theoretical calculation of tidal Love numbers of the Moon with a new spectral element method

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Earth and Planetary Physics 2022年第3期6卷 241-247页

作者： BinBin Liao XiaoDong Chen jianqiao xu JiangCun Zhou HePing Sun State Key Laboratory of Geodesy and Earth’s Dynamics Innovation Academy for Precision Measurement Science and TechnologyChinese Academy of SciencesWuhan 430077China University of the Chinese Academy of Sciences Beijing 100049China

The tidal Love numbers of the Moon are a set of nondimensional parameters that describe the deformation responses of the Moon to the tidal forces of external celestial bodies.They play an important role in the theoretical calculation of the Moon’s tidal deformation and the inversion of its internal structure.In this study,we introduce the basic theory for the theoretical calculation of the tidal Love numbers and propose a new method of solving the tidal Love numbers:the spectral element method.Moreover,we explain the mathematical theory and advantages of this method.On the basis of this new method,using 10 published lunar internal structure reference models,the lunar surface and lunar internal tidal Love numbers were calculated,and the influence of different lunar models on the calculated Love numbers was analyzed.Results of the calculation showed that the difference in the second-degree lunar surface Love numbers among different lunar models was within 8.5%,the influence on the maximum vertical displacement on the lunar surface could reach±8.5 mm,and the influence on the maximum gravity change could reach±6μGal.Regarding the influence on the Love numbers inside the Moon,different lunar models had a greater impact on the Love numbers h_(2) and l_(2) than on k_(2) in the lower lunar mantle and core.

关键词： lunar tidal Love numbers spectral element method solid lunar tides lunar internal structure reference models lunar tidal deformation theory

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基于改进主成分分析法的水环境中重金属污染流域水质生态评价方法研究

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环境科学与管理 2024年第5期49卷 191-194页

作者：徐剑乔中铁第四勘察设计院集团有限公司湖北武汉430063

为了准确掌握水环境中的重金属污染情况,提高水质生态防治效果,提出了基于改进主成分分析法的水环境中重金属污染流域水质生态评价方法研究。选取研究污染流域水质区域,收集4个区域地表水,测定金属元素含量,通过四类分析与评价法,实现... 详细信息

为了准确掌握水环境中的重金属污染情况,提高水质生态防治效果,提出了基于改进主成分分析法的水环境中重金属污染流域水质生态评价方法研究。选取研究污染流域水质区域,收集4个区域地表水,测定金属元素含量,通过四类分析与评价法,实现对水环境中重金属污染状况及潜在危害的生态评价,得出评价的B区域和C区域水质综合重金属污染较高,铁元素在四个区域均在第一主成分,是污染程度最高的,整体生态评价为及格。评价结果表明所提方法可以对水环境中重金属污染状况进行精确的评价,辅助保护人民身体健康与生态环境。

关键词：改进主成分分析法潜在生态风险水生态环境重金属污染水质生态评价

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用钻孔应变数据探测2011年日本Tohoku大地震激发的低频地球环型自由振荡及其谱峰分裂

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地球物理学报 2024年第4期67卷 1383-1397页

作者：张赓徐建桥陈晓东张凌云孙和平龚立卓中国科学院精密测量科学与技术创新研究院大地测量与地球动力学国家重点实验室武汉430077 中国科学院大学地球与行星科学学院北京100049 华北理工大学矿业工程学院河北唐山063210

地震激发的地球自由振荡中,环型自由振荡(特别是低频环型自由振荡)的精确探测相比于球型自由振荡更加困难.环型自由振荡对SH波速度结构更加敏感,能更好地监测走滑断层运动,因此精确估算环型自由振荡的谱峰参数可为地球内部大尺度SH波速... 详细信息

地震激发的地球自由振荡中,环型自由振荡(特别是低频环型自由振荡)的精确探测相比于球型自由振荡更加困难.环型自由振荡对SH波速度结构更加敏感,能更好地监测走滑断层运动,因此精确估算环型自由振荡的谱峰参数可为地球内部大尺度SH波速度结构和大地震的震源机制提供更强约束.本研究利用2011年日本Tohoku地震后四分量钻孔应变仪的观测资料,提取了该地震激发的1.3 mHz以下低频环型和球型自由振荡信号,与STS-1宽频带地震仪的结果相比较,发现四分量钻孔应变仪对1 mHz以下的环型自由振荡具有更强的探测能力.本研究还采用频率域自回归方法精确估计了0T2—0T6的简并频率,结果与PREM模型理论值相差非常小,平均相对误差仅为2.52×10^(-4).此外还用钻孔应变仪观测资料探测到了0T2谱峰分裂现象.研究结果表明,钻孔应变仪能有效探测到大地震激发的低频地球环型自由振荡信号,可为地幔大尺度各向异性结构研究提供高质量的基础数据.

关键词：环型自由振荡钻孔应变仪 Tohoku地震简正模谱峰分裂 STS-1地震仪

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Research Progress in Surface and Marine Gravimetry

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测绘学报:英文版 2023年第3期6卷 19-32页

作者： Heping SUN Lifeng BAO Shi CHEN Xiaoming CUI Qianqian LI Lulu JIA jianqiao xu Jiangcun ZHOU Minzhang HU Yiqing ZHU Xiaodong CHEN Lin WU Jiancheng HAN Honglei LI Miaomiao ZHANG Linhai WANG Innovation Academy for Precision Measurement Science and Technology Chinese Academy of SciencesWuhan 430077China State Key Laboratory of Geodesy and Earth’s Dynamics Innovation Academy for Precision MeasurementUniversity of Chinese Academy of Sci-encesBeijing 100049China Institute of Geophysics China Earthquake AdministrationBeijing 100081China Beijing Baijiatuan Earth Sciences National Observation and Research Station Beijing 100095China Institute of Seismology China Earth-quake AdministrationWuhan 430071China Second Monitoring Center China Earthquake AdministrationXi’an 710054China

Gravity field is the most basic physical field generated by the material properties of the Earth system.It reflects the spatial distribution,movement and change of materials determined by the interaction and dynamic process inside the Earth.Over the years,a variety of technical means have been used to detect the Earth’s gravity field and supported numerous studies on the global change,resource detection,geological structure movement,water resources change and other related fields of research.Here is part of the progress in surface and marine gravimetry obtained by Chinese geodesy scientists from 2019 to 2023 from the following aspects,including:①Continuous gravity network in Chinese mainland;②Application of superconducting gravity measurement;③Network adjustment for continental-scale gravity survey campaign and data quality control;④Regional time-variable gravity field and its application;⑤Research progress on novel technologies for gravity inversion;⑥Research progress on marine gravity field determination;⑦Application research on marine gravity field.

关键词： surface and marine gravimetry time-variable gravity field geodynamics gravity inversion

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