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Suitable region of dynamic optimal interpolation for efficiently altimetry sea surface height mapping

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geodesy and Geodynamics 2024年第2期15卷 142-149页

作者： Jiasheng Shi Taoyong Jin School of geodesy and Geomatics Hubei Luojia LaboratoryWuhan UniversityWuhan 430079China MOE key laboratory of geospace environment and geodesy Wuhan UniversityWuhan 430079China

The dynamic optimal interpolation(DOI)method is a technique based on quasi-geostrophic dynamics for merging multi-satellite altimeter along-track observations to generate gridded absolute dynamic topography(ADT).Compared with the linear optimal interpolation(LOI)method,the DOI method can improve the accuracy of gridded ADT locally but with low computational ***,considering both computational efficiency and accuracy,the DOI method is more suitable to be used only for regional *** this study,we propose to evaluate the suitable region for applying the DOI method based on the correlation between the absolute value of the Jacobian operator of the geostrophic stream function and the improvement achieved by the DOI *** verifying the LOI and DOI methods,the suitable region was investigated in three typical areas:the Gulf Stream(25°N-50°N,55°W-80°W),the Japanese Kuroshio(25°N-45°N,135°E-155°E),and the South China Sea(5°N-25°N,100°E-125°E).We propose to use the DOI method only in regions outside the equatorial region and where the absolute value of the Jacobian operator of the geostrophic stream function is higher than1×10^(-11).

关键词： Dynamic optimal interpolation Linearoptimal interpolation Satellite altimetry Sea surface height Suitable region

Numerical simulations of earthquake rupture induced by pressure perturbation

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geodesy and Geodynamics 2024年第5期15卷 477-487页

作者： Bingquan Ren Caijun Xu Guoyan Jiang Lei Yang School of geodesy and Geomatics Wuhan UniversityWuhan 430079China key laboratory of geospace environment and geodesy Ministry of EducationWuhan UniversityWuhan 430079China key laboratory of Geophysical geodesy Ministry of Natural ResourcesWuhan 430079China

The subsurface fluid injection can cause pressure increase within faults,leading to earthquake ***,the factors controlling earthquake rupture due to pressure perturbation remain poorly *** resolve this problem,we simulate the physical processes of earthquake nucleation and rupture on strike-slip faults perturbated by pressure migration based on the slip-weakening *** kinds of factors,including background stress,fluid injection rates,the area of the pressurized region,fault geometry,and fault friction coefficients,are considered in our *** simulation results reveal that the ratio of shear stress to normal stress rather than their absolute values controls the rupture *** the large stress ratios,high injection rates,and large pressurized areas,earthquakes are prone to propagate as runaway ***,faults with large aspect ratios of length to width are also favorable for causing runaway *** contrast,the factors of fault strike,dip angles and friction coefficients have minor influence on rupture behavior.

关键词： Induced seismicity Finite element simulation Rupture mode

Reassessing the contributions of terrestrial waters to sea level variations in the South China Sea and its response to alternating ENSO events

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Science China Earth Sciences 2024年第7期67卷 2253-2267页

作者： Pengfei YANG Hok Sum FOK Zhongtian MA MOE key laboratory of geospace environment and geodesy&MNR key laboratory of Geophysical geodesy School of Geodesy and GeomaticsWuhan UniversityWuhan 430079China Hubei Luojia laboratory Wuhan 730079China Department of Land Surveying and Geo-Informatics The Hong Kong Polytechnic UniversityHong Kong 999077China

Regional sea level variability is linked to regional terrestrial water and the El Ni?o-Southern Oscillation(ENSO).This study assessed the relationships between the sea level variations in the South China Sea(SCS)and ENSO,the impact of terrestrial water storage(TWS)on non-steric sea level(NSSL),and the contributions of steric sea level(SSL)and NSSL to sea level anomaly(SLA),*** 2003 to 2015,the SLAs exhibited a long-term trend of 6.65±0.78 mm/yr,which was primarily attributed to the ***,during 2003-2015,ENSO events alternating with varying intensities might also be responsible for the unusually high SLA *** to the SSLs,the NSSLs contributed the seasonal signals to the SLAs,while the NSSLs changes were largely explained by the TWS in the Mekong River Basin at the seasonal scale and in the Pearl River Basin and Red River Basin at other time *** contrast to the TWS,the contributions of precipitation and evapotranspiration were relatively minor.A negative correlation between the sea level variations and ENSO was also found,with cross-correlation coefficients between the oceanic Ni?o index and SLAs/SSLs/NSSLs of -0.36/-0.37/-0.62 with lags of 2/3/2 months,*** findings systematically reassessed the contributions of different components to the sea level *** study provided a benchmark for in-depth analysis of the impacts of terrestrial water and other potential causes on sea level rise in the SCS.

关键词： South China Sea Sea level variations Terrestrial water storage ENSO

Coseismic Coulomb stress changes induced by a 2020-2021 M_(W)>7.0 Alaska earthquake sequence in and around the Shumagin gap and its influence on the Alaska-Aleutian subduction interface

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geodesy and Geodynamics 2024年第1期15卷 1-12页

作者： Lei Yang Jianjun Wang Caijun Xu School of geodesy and Geomatics Wuhan UniversityWuhan 430079China Collaborative Innovation Center of Geospatial Technology Wuhan 430079China key laboratory of geospace environment and geodesy Ministry of EducationWuhan UniversityWuhan 430079China

Three M_(W)>7.0 earthquakes in 2020-2021 occurred in the Shumagin seismic gap and its adjacent area of the Alaska-Aleutian subduction zone,including the Mw7.8 Simeonof thrust earthquake on July 22,2020,the M_(W)7.6 Sand Point strike-slip earthquake on October 19,2020,and the M_(W)8.2 Chignik thrust earthquake on July 29,*** spatial and temporal proximity of these three earthquakes prompts us to probe stress-triggering effects among *** we examine the coseismic Coulomb stress change imparted by the three earthquakes and their influence on the subduction *** results show that:(1)The Simeonof earthquake has strong loading effects on the subsequent Sand Point and Chignik earthquakes,with the Coulomb stress changes of 3.95 bars and 2.89 bars,*** Coulomb stress change caused by the Sand Point earthquake at the hypocenter of the Chignik earthquake is merely around 0.01 bars,suggesting the negligible triggering effect on the latter earthquake;(2)The triggering effects of the Simeonof,Sand Point,and Chignik earthquakes on aftershocks within three months are not well pronounced because of the triggering rates of 38%,14%,and 43%*** factors may have played an important role in promoting the occurrence of these aftershocks,such as the roughness of the subduction interface,the complicated velocity structure of the lithosphere,and the heterogeneous prestress therein;(3)The three earthquakes caused remarkable coseismic Coulomb stress changes at the subduction interface nearby these mainshocks,with an average Coulomb stress change of 3.2 bars in the shallow region directly inwards the trench.

关键词： The 2020-2021 Alaska earthquake sequence Coseismic Coulomb stress change Mainshock-aftershock triggering The Alaska-Aleutian subduction interface The Shumagin gap

Present-day movement characteristics of the Qinghai Nanshan fault and its surrounding area from GPS observation

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geodesy and Geodynamics 2024年第2期15卷 133-141页

作者： Yang Liu Yuxuan Qiu Jialiang Liu Luyun Xiong Caijun Xu Jianghui Geng Gang Zheng Tianchen Sheng School of geodesy and Geomatics Wuhan UniversityWuhan 430079China key laboratory of geospace environment and geodesy Ministry of EducationWuhan UniversityWuhan 430079China key laboratory of Geophysical geodesy Ministry of Natural ResourcesWuhan UniversityWuhan 430079China GNSS Research Center Wuhan UniversityWuhan 430079China School of Earth and environment University of LeedsLeeds LS29JTUK Qinghai Basic Surveying and Mapping Institute Xining 810101China

The Qinghai Nanshan fault is a larger fault in the Northeastern Xizang *** previous studies,its movement characteristics are mainly investigated with geological and seismic observations,and the tectonic transformation role of the fault on its east is not yet *** study uses data fusion to obtain denser GPS observations near the Qinghai Nanshan *** on tectonic characteristics,we establish a block model to investigate the fault slip rate,locking degree,and slip *** results show that the Qinghai Nanshan fault slip rate is characterized by sinistral and convergent *** the sinistral and convergent rates display a decreasing trend from west to *** locking degree and slip deficit are higher in the western segment(with an average of about 0.74 and 1.1 mm/a)and lower in the eastern ***,we construct a strain rate field using GPS observations to analyze the regional strain *** results indicate that along the fault,the western segment shows a larger shear strain rate and negative dilation *** earthquake records show that the frequency of earthquakes is lower near the *** joint results suggest that the western segment may have a higher earthquake *** addition,the insignificant fault slip rate in the eastern segment may indicate that it does not participate in the tectonic transformation among the Riyueshan,Lajishan,and West Qinling faults.

关键词： The Qinghai Nanshan fault Movement characteristics Block model Slip rate GPS

Long-term variation of Arctic Sudden Stratospheric Warmings(SSW) and potential causes

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Earth and Planetary Physics 2024年第5期8卷 742-752页

作者： QingRan Li ShaoDong Zhang KaiMing Huang ChunMing Huang Yun Gong WenTao Tang Zheng Ma School of Electronic Information Wuhan University Guizhou Normal University key laboratory of geospace environment and geodesy Ministry of Education State key laboratory of Information Engineering in Surveying Mapping and Remote Sensing School of Electronic Information Engineering Jingchu University of Technology

Utilizing the European Centre for Medium-Range Weather Forecast(ECMWF) Reanalysis v5(ERA5), for the first time, we have confirmed close links among Sudden Stratospheric Warmings(SSWs) in the Northern Hemisphere(NH), the polar vortices, and stratospheric Planetary Waves(PWs) by analyzing and comparing their trends. Interestingly, within overall increasing trends, the duration and strength of SSWs exhibit increasing and decreasing trends before and after the winter of 2002, respectively. To reveal possible physical mechanisms driving these trends, we analyzed the long-term trends of the winter(from December to February) polar vortices and of stratospheric PWs with zonal wave number 1. Notably, our results show that in all three time periods(the entire period of 41winters, 1980 to 2020, and the two subperiods — 1980-2002 and 2002-2020) enhancing SSWs were always accompanied by weakening winter polar vortices and strengthening polar PWs like Stationary Planetary Waves(SPWs) and 16-day waves, and vice versa. This is the first proof, based on ERA5 long-term trend data, that weakening polar vortices and enhancing stratospheric PWs(especially SPWs) could cause an increase in SSWs.

关键词： sudden stratospheric warmings stationary planetary waves 16-day waves polar vortrices long-term trend correlation coefficient

Global hybrid simulations of soft X-ray emissions in the Earth’s magnetosheath

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Earth and Planetary Physics 2024年第1期8卷 47-58页

作者： Jin Guo TianRan Sun San Lu QuanMing Lu Yu Lin XueYi Wang Chi Wang RongSheng Wang Kai Huang School of Earth and Space Sciences University of Science and Technology of ChinaHefei 230026China CAS Center for Excellence in Comparative Planetology/CAS key lab of geospace environment University of Science and Technology of ChinaHefei 230026China Collaborative Innovation Center of Astronautical Science and Technology Harbin 150001China National Space Science Center Chinese Academy of SciencesBeijing 100190China Physics Department Auburn UniversityAuburnALUSA

Earth’s magnetopause is a thin boundary separating the shocked solar wind plasma from the magnetospheric plasmas,and it is also the boundary of the solar wind energy transport to the *** X-ray imaging allows investigation of the large-scale magnetopause by providing a two-dimensional(2-D)global view from a *** performing 3-D global hybrid-particle-in-cell(hybrid-PIC)simulations,we obtain soft X-ray images of Earth’s magnetopause under different solar wind conditions,such as different plasma densities and directions of the southward interplanetary magnetic *** all cases,magnetic reconnection occurs at low latitude *** soft X-ray images observed by a hypothetical satellite are shown,with all of the following identified:the boundary of the magnetopause,the cusps,and the *** X-ray emissivity in the magnetosheath is characterized by large amplitude fluctuations(up to 160%);however,the maximum line-of-sight-integrated X-ray intensity matches the tangent directions of the magnetopause well,indicating that these fluctuations have limited impact on identifying the magnetopause boundary in the X-ray ***,the magnetopause boundary can be identified using multiple viewing *** also find that solar wind conditions have little effect on the magnetopause *** Solar wind Magnetosphere Ionosphere Link Explorer(SMILE)mission will provide X-ray images of the magnetopause for the first time,and our global hybrid-PIC simulation results can help better understand the 2-D X-ray images of the magnetopause from a 3-D perspective,with particle kinetic effects considered.

关键词： magnetopause X-ray emissivity X-ray imaging SMILE global hybrid-PIC simulation

Constraint on the focal mechanism of the 2011 Tohoku earthquake from the radial modes

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geodesy and Geodynamics 2024年第1期15卷 27-32页

作者： Weikun Chen Hao Ding School of geodesy and Geomatics Hubei LuoJia LaboratoryWuhan UniversityWuhan 430079China

Different from other normal modes of the Earth’s free oscillation that depend on all the six components(M_(rr),M_(tt),M_(pp),M_(rt),M_(rp),and M_(tp))of the centroid moment tensor,the amplitudes of the radial modes depend on the M_(rr)component(e.g.,scalar moment(M_(0)),dip(δ),and slip(λ))and hypocenter depth of the focal mechanism,and hence can be easily used to constrain these parameters of the focal *** this study,we use the superconducting gravimeter(SG)records after the 2011 Tohoku earthquake to analyze the radial modes_(0)S_(0)and_(1)S_(0).Based on the solutions of the focal mechanism provided by the GCMT and USGS,we can obtain the theoretical amplitudes of these two radial *** the theoretical amplitudes with the observation amplitudes,it is found that there are obvious differences between the former and the latter,which means that the GCMT and USGS focal mechanisms cannot well represent the real focal mechanism of the 2011 *** the GCMT solution as a reference and changing the depth and the three parameters of the M_(rr)moment,the scalar moment(M_(0))and the dip(δ)have significant influences,but the effects of the slip(λ)and the depth are *** comparisons,we provide a new constraint(M_(0)=5.8±0.09×10^(22)N·m,δ=10.1±0.08°,λ=88°,and depth=20 km)for the focal mechanism of the 2011 *** addition,we further determine the center frequency(1.631567±2.6e^(-6)mHz)and quality factor(2046.4±50.1)of the_(1)S_(0)mode.

关键词： Focal mechanism Radial modes Gravity observation

A global empirical model for estimating zenith tropospheric delay

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Science China Earth Sciences 2016年第1期59卷 118-128页

作者： YAO Yi Bin ZHANG Bao XU Chao Qian HE Chang Yong YU Chen YAN Feng School of geodesy and Geomatics Wuhan University key laboratory of geospace environment and geodesy Ministry of Education

Tropospheric delay acts as a systematic error source in the Global Navigation Satellite Systems(GNSS) positioning. Empirical models UNB3, UNB3 m, UNB4 and EGNOS have been developed for use in Satellite-Based Augmentation Systems(SBAS). Model performance, however, is limited due to the low spatial resolution of the look-up tables for meteorological parameters. A new design has been established in this study for improving performance of the tropospheric delay model by more effectively eliminating the error produced by tropospheric delay. The spatiotemporal characteristics of the Zenith Tropospheric Delay(ZTD) were analyzed with findings that ZTD exhibits different annual variations at different locations and decreases exponentially with height increasing. Spherical harmonics are utilized based on the findings to fit the annual mean and amplitude of the ZTD on a global scale and the exponential function is utilized for height corrections, yielding the ZTrop model. On a global scale, the ZTrop features an average deviation of ?1.0 cm and Root Mean Square(RMS) of 4.7 cm compared with the International GNSS Service(IGS) ZTD products, an average deviation of 0.0 cm and RMS of 4.5 cm compared with the Global Geodetic Observing System(GGOS) ZTD data, and an average deviation of ?1.3 cm and RMS of 5.2 cm compared with the ZTD data from the Constellation Observing System of Meteorology, Ionosphere, and Climate(COSMIC). The RMS of the ZTrop model is 14.5% smaller than that of UNB3, 6.0% smaller than that of UNB3 m, 16% smaller than that of UNB4, 14.5% smaller than that of EGNOS and equivalent to the sophisticated GPT2+Saas model in comparison with the IGS ZTD products. The ZTrop, UNB3 m and GPT2+Saas models are finally evaluated in GPS-based Precise Point Positioning(PPP), as the models act to aid in obtaining PPP position error less than 1.5 cm in north and east components and relative large error(>5 cm) in up component with respect to the random walk approach.

关键词： Zenith tropospheric delay Spherical harmonics Exponential function ZTrop model