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gravity change and its mechanism after the first water impoundment in Three Gorges Project

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Acta Seismologica Sinica(English Edition) 2006年第5期19卷 522-529页

作者：孙少安项爱民朱平申重阳 Institute of Seismology China Earthquake Administration Crustal Movement Laboratory Wuhan 430071China Wuhan Base of the Institute of Crustal Dynamics China Earthquake AdministrationWuhan 430071China Institute of Geophysics China Earthquake Administration

In this paper we have analyzed precise gravity survey and gravity effects resulted from water loading, crustal deformation, ground water level change and precipitation before and after the water impoundment in the Three Gorges Reservoir. We found that： ① In dam area of the reservoir, gravity effect resulted from water load increase is the most significant, maximum gravity change is 200×10^-8 m/s^2, but this effect is limited in amplitude and range. gravity change can be observed about 5 km offshore. The gravity change caused by ground water level change is regional; and the impact of precipitation on it should not be neglected. ② At head area of the reservoir, the maximum gravity change is near Xiangxi. Monitoring the variation of gravity field and further study should continue in the future.

关键词： the Three Gorges Project the first water impoundment gravity change

gravity change observed in a local gravity network and its implication to seasonal precipitation in Dali county, Yunnan province, China

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Earthquake Science 2014年第1期27卷 79-88页

作者： Xin Zhou Wenke Sun Hui Li Shuhei Okubo Shaoan Sun Lelin Xing Dongzhi Liu Chongyang Shen Laboratory of Computational Geodynamics University of Chinese Academy of Sciences Institute of Seismology China Earthquake Administration Earthquake Research Institute The University of Tokyo

This study investigates data-processing methods and examines the precipitation effect on gravity measurements at the Dali gravity network, established in 2005. High-quality gravity data were collected during four measurement campaigns. To use the gravity data validly, some geophysical corrections must be considered carefully. We first discuss data-processing methods using weighted least- squares adjustment with the constraint of the absolute gravity datum. Results indicate that the gravity precision can be improved if all absolute gravity data are used as constraints and if calibration functions of relative gravi- meters are modeled within the observation function. Using this data-processing scheme, the mean point gravity pre- cision is better than 12 μgal. After determining the best data-processing scheme, we then process the gravity data obtained in the four measurement campaigns, and obtain gravity changes in three time periods. Results show that the gravity has a remarkable change of more than 50 pgal in the first time period from Apr-May of 2005 to Aug-Sept of 2007. To interpret the large gravity change, a mean water mass change （0.6 m in height） is assumed in the ETOPO1 topographic model. Calculations of the precipitation effect on gravity show that it can reach the same order of the observed gravity change. It is regarded as a main source of the remarkable gravity change in the Dali gravity network, suggesting that the precipitation effect on gravity mea- surements must be considered carefully.

关键词： gravity network gravity change gravity datum Weighted constraint Precipitationeffect

Relationship between gravity change and Yangbi M_(S)6.4 earthquake

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Geodesy and Geodynamics 2023年第4期14卷 321-330页

作者： Xiong Yang Yiqing Zhu Yunfeng Zhao Shouchun Wei The Second Monitoring and Application Center China Earthquake AdministrationXi'an 710054China

Based on the relative and absolute gravity measurements in the southern South-North Seismic Belt since 2015,we analyzed the dynamic change of the regional gravity field and its relationship with the Yangbi M_(S)6.4 earthquake that occurred on May 21,*** results show that:(1)The regional gravity field changes are closely related to the Weixi-Qiaohou fault,which reflects the surface gravity field changes caused by the fault activity from 2015 to 2021;(2)The gravity field change related to the preparation of Yangbi earthquake has experienced the evolution process of"steady state-regional gravity anomaly-local gravity anomaly-four-quadrant distribution-large area positive anomaly-earthquake occurring in the reverse change process";(3)The cumulative and differential change images of the gravity field show that there were significant gravity changes in the two years preceding the Yangbi earthquake,and the earthquake occurred in the high-gradient belt of gravity variation,the center of the four-quadrant,and close to the zero contour turn;(4)The dynamic evolution image of the gravity field can well reflect the precursory phenomena during the preparation for the Yangbi MS6.4 *** on the anomaly change of mobile gravity,a certain degree of medium-term prediction was made before the Yangbi M_(S)6.4 earthquake,especially the determination of strong earthquake location.

关键词： South-north seismic belt Yangbi earthquake gravity observation gravity change

gravity change Caused by Heavy Rainfall Detected by A gPhone Gravimeter in Zhengzhou， China

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Journal of Earth Science 2021年

作者： LeLin Xing YuFei Han XiaoWei Niu Lei Bai Innovation Academy for Precision Measurement Science and Technology， Chinese Academy of Sciences State Key Laboratory of Geodesy and Earth's Dynamics， Chinese Academy of Sciences China Earthquake Networks Center University of Chinese Academy of Sciences

The short-term effect of heavy rainfall on gPhone gravimeter observation at Zhengzhou seismic station is investigated. According to the observation data during 2021-07-17～07-20， the corrected gravity residual reflects the gravimetric response caused by heavy rainfall. The observed gravity change is dominated by the local effect considering topographic effect on gravity. The deduced water depth near the observation station is about 300 mm.

关键词： gravity gravity change heavy rain gravimeter gPhone

Simulation of co-seismic gravity change and deformation of Wenchuan Ms8.0 earthquake

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Geodesy and Geodynamics 2010年第1期1卷 8-14页

作者： Chongyang Shen Hui Li Hongbo Tan Institute of Seismology China Earthquake Administration Wuhan 430071 China Crustal Movement Laboratory Wuhan 430071 China

Surface co-seismic gravity changes and displacements caused by the Wenchuan Ms8.0 earthquake are calculated on the basis of the half-space dislocation theory and two fault models inversed, respectively, by Institute of Geophysics, CEA and USGS. The results show that 1 ） the dislocation consists of dip slip and rightlateral strike slip ;2 ）the co-seismic gravity change shows a four-quadrant pattern ,which is greatly controlled by the distribution of the vertical displacements, especially in the near-filed ; 3 ） the gravity change is generally less than 10 × 10^-8 ms^-2 in the far-field,but as high as several 100 × 10^-8 ms^-2 in the near-filed. These results basically agree with observational results.

关键词： Wenchuan earthquake dislocation theory gravity change deformation simulation

Effects of Gaussian filter in processing GRACE data: gravity rate of change at Lhasa,southern Tibet

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Science China Earth Sciences 2011年第9期54卷 1378-1385页

作者： SUN WenKe HASEGAWA Takashi ZHANG XinLin FUKUDA Yoichi SHUM C. K. WANG Lei Key Laboratory of Computational Geodynamics Graduate University of Chinese Academy of Sciences Beijing 100049 China Department of Geophysics Kyoto University Japan Earthquake Research Institute The University of Tokyo Japan Division of Geodetic Science School of Earth Sciences The Ohio State University OH 43210-1398 USA

In this paper, the spatial gravity distribution over Tibetan Plateau and the gravity rate of change at Lhasa for different Gaussian filter radii are computed using GRACE data. Results show that the estimate of the gravity rate of change is spatialradius-dependent of the Ganssian filter. The GRACE-estimated gravity rate of change agrees well with the surface measured one. In other words, the GRACE-estimated gravity rate of change has a limited value as that obtained by surface measurement when the spatial filter radius reaches zero. Then numerical simulations are made for different spatial radii of the Gaussian filter to investigate its behaviors when applied to surface signals. Results show that the estimate of a physical signal is filter-radius dependent. If the computing area is equal to or less than the mass area, especially for a uniformly distributed mass, the estimate gives an almost correct result, no matter what filter radius is used. The estimate has large error because of the signal leakage caused by harmonic truncation if the computing area is much bigger than the mass distribution （or inverse for a small mass anomaly）. If a mass anomaly is too small, it is difficult to recover it from space observation unless the filter radius is extremely small. If the computing point （or area） is outside the mass distribution, the estimated result is almost zero, particularly for small filter radii. These properties of the Gaussian filter are helpful in applying GRACE data in different geophysical problems with different spatial position and geometrical size. We further discuss physical sources causing the scalar gravity change at Lhasa. Discussions indicate that the gravity rate of change at Lhasa is not caused by the present-day ice melting （PDIM）（or Little Ice Age, LIA） effect because no ice melting occurs in Lhasa city and nearby. The gravity rate of change is attributable mainly to tectonic deformation associated with the Indian Plate collision. Simultaneous surf

关键词： gravity change GRACE Gaussian filter Tibetan Plateau Lhasa

Viscous lithospheric structure beneath Sumatra inferred from post-seismic gravity changes detected by GRACE

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Science China Earth Sciences 2011年第8期54卷 1257-1267页

作者： WANG WuXing SHI YaoLin SUN WenKe ZHANG Jing Institute of Earthquake Science China Earthquake Administration Beijing 100036 China Laboratory of Computational Geodynamics Graduate University of Chinese Academy of Sciences Beijing 100049 China

Satellite gravity data of the regional rheological structure of the lithosphere in the vicinity of Sumatra is used as evidence to enable a better understanding of the regional geodynamic *** data is interpreted using the theory of post-seismic viscoelastic *** post-seismic changes in the gravity field resulting from the 2004 M w 9.3 Sumatra earthquake were calculated from gravity Recovery and Climate Experiment (GRACE) satellite data.A spatial Gaussian filter,500 km wide,was used in the *** results indicate that there were significant co-seismic jumps in both uplifted and subducted *** magnitude of the jump in the subducted zone was ～9 10 8 m/s 2,more significant than the ～2 10 8 m/s 2 jump observed in the uplifted ***,a positive gravity change occurred in the uplifted zone very soon after the *** rheological structure of the lithosphere has a great effect on deformation and its determination is a fundamental part of developing reliable numerical simulations in *** on the temporally-variable gravity field observed by GRACE,the viscous lithospheric structure of the Sumatra area is investigated with a self-gravitating,half space,viscoelastic earth *** estimated viscosity is of the order of 1.0 10 18 Pa·s and there are differences in the rheological parameters on the two sides of the *** factors that affect the viscosity are discussed in connection with the tectonic structure of the Sumatra area.

关键词： Sumatra earthquake GRACE gravity change viscous structure

Coulomb stress and gravity changes associated with the 2016 Mw 7.8 Kaikoura Earthquake, New Zealand: Application for aftershock triggering and fault interaction process analysis

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Journal of Mountain Science 2021年第2期18卷 510-527页

作者： HASSAN Abubakr HUANG Ding-fa JIANG Zhong-shan ZHANG Lu-peng Faculty of Geosciences and Environmental Engineering Southwest Jiaotong UniversityChengdu 611756China Surveying Engineering Department Faculty of EngineeringKarary UniversityKhartoum 12304Sudan

The Kaikoura earthquake on November 14,2016 is one of the largest and most complex earthquakes in New Zealand since *** the fact that it has ruptured about 12 separate faults,triggered 2132 aftershocks within one week of the mainshock and induced considerable stress changes,few studies have been conducted to comprensively investigate the *** current study examines the horizontal and vertical displacements as well as the stress and gravity changes,aftershock distributions and also find out whether these changes affect the surrounding regions along the complex fault *** study covers the entire area affected by the Kaikoura event,which includes the northern part of the South Island and the southern part of the North *** dislocation theory was employed to evaluate the coseismic slip model on the multiple *** displacement results revealed that the maximum horizontal displacement is about 6 m and the vertical about 2 m,which are reasonably consistent with earlier study ***,the stress and gravity changes are quite complicated and inhomogeneous as evidenced by our coseismic model,demonstrating the complexity of the Kaikoura earthquake as *** all the aftershocks are distributed in places where the stress and gravity change are found to be *** order to investigate the stability of our stress change models,we applied different friction coefficients and receiver fault *** results justify the friction coefficient(μ=0.4)and the receiver fault parameters(230°,70°,150°)are suitable to define good stress change *** to the stress change results at 15 km depth,the northern parts of the mainshock region,Hundalee fault,Humps fault and Jordan thrust areas together with the Wellington area are closer to failure and situated in a seismic risk *** multidimensional analysis adopted in this paper is helpful for making decisions and applications of stress and gravity change models in

关键词： Aftershock triggering Components displacement Coulomb failure stress Fault interaction gravity change Kaikoura earthquake

Surface deformation and gravity changes caused by dilatancy in a layered elastic-vis-coelastic half space

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Acta Seismologica Sinica(English Edition) 1997年第4期10卷 74-79页

作者：王勇许厚泽 1. Institute of Geodesy and Geophysics Chinese Academy of Sciences 430077 Wuhan China

Surface deformation and gravity changes caused by dilatancy with magmatic intrusion (Mogi model) in two elastic layers overlying a Maxwell viscoelastic half space were systematically studied. We focused on the numerical calculation technique and the discussion of the effects of rheological properties of Maxwell half spqce on vertical displacements and gravity changes. The results show that the rheological properties of materials has an apparent effect on the results, when the intrusion was placed under Moho discontinuity, and has smaller effect if the intrusion was placed inside the crust. Therefore the elastic model is valid for considering the gravity changes or deformation caused by dilatancy with magmatic intrusion within the crust. The model and numerical calculation technique in this study can be used to model and interpret the long term deformation and gravity observations in volcanic, seismic and geothermal regions.

关键词： gravity change crustal deformation dilatancy viscoelasticity