Non-tidal ocean loading (NTOL) is a significant environmental factor affecting gravity observations especially in coastal areas. Its non-periodic characteristics and regional dependence increase the difficulty of data analysis and signal separation. The Haikou superconducting gravimetry station, located in the northern part of Hainan Island, is situated close to the South China Sea. It is influenced by complex regional oceanic dynamic processes, and the NTOL signal in its gravity observations is particularly prominent. Based on continuous superconducting gravimeter (SG) observations from the iGrav-048 at the Haikou station and high-resolution global sea surface height data from the Copernicus Marine Environment Monitoring Service (CMEMS), we calculate the gravity variations and vertical deformations caused by NTOL in the South China Sea using the mass-loading Green’s function convolution method. The estimates are validated by comparison with products from the MPIOM model provided by the GFZ Helmholtz Centre for Geosciences. The results show that NTOL signals in the South China Sea should be the primary source of gravity residuals at the Haikou station. The CMEMS model shows a correlation coefficient of 0.83 with the observations. The maximum gravity change due to NTOL is estimated to be 2.6 μGal based on the CMEMS model. While the CMEMS and MPIOM models show good agreement in overall trend (R = 0.87), CMEMS performs better in simulating high-frequency signals due to its higher spatio-temporal resolution. This highlights the importance of high-precision regional ocean models for improving the modeling and correction of NTOL signals. This study systematically evaluates the impact of South China Sea NTOL on SG observations at the Haikou station, providing a scientific basis for the processing of coastal gravity data in the region. The findings suggest that incorporating NTOL corrections into coastal superconducting gravity data processing can effectively improve data reliability and geophysical interpretation, offering valuable insights for advancing regional ocean loading effect research and related geodetic applications.

The precise extraction of tidal signals from non-stationary gravity observations is a central challenge in geophysics, where accuracy is often limited by mode mixing in data pre-processing algorithms. This study evaluates the performance of the Time-Varying Filter-based Empirical Mode Decomposition (TVF-EMD) method to address this issue. We employed a progressive validation pipeline: the method was first verified on simulated signals, then rigorously tested against a high-fidelity benchmark from a superconducting gravimeter, and finally applied to one month of continuous data from an Atom Gravimeter at the Yilan station. Results demonstrate that TVF-EMD dramatically suppresses mode mixing, with the energy of transient spikes in its residual being an order of magnitude lower than that from the conventional Ensemble Empirical Mode Decomposition method. The tidal signal reconstructed by TVF-EMD achieved the highest cross-correlation coefficient and the smallest root mean square error when compared to the theoretical gravity tide. Subsequent harmonic analysis confirmed that TVF-EMD yielded the lowest errors across all major tidal constituents. These findings validate TVF-EMD as a superior pre-processing framework for tidal analysis, particularly for enhancing the reliability of geophysical parameter inversion from short-duration records obtained with next-generation quantum sensors.

Precise calibration of the superconducting gravimeter (SG) is essential for high-fidelity geodynamic monitoring. This study comparatively evaluates four data pairing strategies for SG calibration using continuous high-frequency absolute gravity data from a Cold Atom Gravimeter (CAG). Using one month of colocated observations at Yilan Station, China, we systematically compare the performance of Single Drop, Running Average, 177-s Block Average, and Traditional Discrete Mode approaches. Power spectral density (PSD) analysis shows that the Single Drop strategy preserves a near-flat spectral profile consistent with white-noise characteristics, while averaging-based strategies modify the spectral characteristics and deviate from ideal whitenoise behavior. With a 5-day continuous observation window, the best-performing strategies achieve a relative precision of 0.087%, exceeding the commonly adopted 0.1% benchmark. The Running Average approach achieves statistical performance close to that of the Single Drop strategy and outperforms the 177-s Block Average in terms of standard error and relative precision. Window duration analysis reveals that while statistical precision improves with longer observations, calibration stability plateaus due to the complex interplay of low-frequency noise and window segmentation. For single-day calibration scenarios, selecting periods with larger tidal amplitude improves relative precision by approximately 22% compared to arbitrary day selection. Overall, this study provides a systematic evaluation of sampling strategies enabled by continuous absolute gravimetry and reveals the trade-off between statistical efficiency and low-frequency stability, offering practical guidance for optimizing SG calibration under realistic observational constraints.

以观测数据与DDW潮汐模型之差的均方根和重力残差为约束,对基于 M2 潮波标定gPhone重力仪格值系数的方法进行改进.利用改进方法对连续重力台网内的 9 台 gPhone 重力仪格值系数进行标定,基于M2 潮波相对误差、残差振幅谱均方根等指标对标定结果进行精度评定,并与 FG5 绝对重力仪比测法、M2 潮波标定法进行比较.结果表明,改进方法的 M2 潮波潮汐因子与理论固体潮模型平均相对误差提高到0.215 2%,残差振幅谱均方根平均达到 1.690 2μGal,与 FG5 比测法精度相当,优于 M2 潮波标定法.最后,讨论格值系数分布规律以及重力残差矢量与台站所在位置的经度依赖关系.

The Debao MS4.8 earthquake occurred in western Guangxi on August 5, 2021, near where the Jingxi MS5.2 earthquake occurred in 2019. To study the increasing seismicity in western Guangxi, it is necessary to determine whether there was an anomaly related to the earthquake source near the Pingxiang gravity station, which is located approximately 100 km from the epicenter of the Debao MS4.8 earthquake. In this study, the R-value scoring method was used to analyze the anomaly and evaluate the prediction efficiency of the double frequency (DF) micro-seismic signal vertical displacement (referred to as vertical displacement, VD) and the absolute value of monthly extreme rate (referred to as the monthly rate). Results show that earthquakes larger than MS4.0 in the 350 km range from the Pingxiang station tend to coincide with yearly typhoons, and the VD of micro-seismic signals correspondingly changes from low to high. The Debao MS4.8 earthquake occurred during a gradual VD increase from 0.05 x 10-6 to 0.10 x 10-6 m. When discussing the relationships among R, the rate threshold, and the effective duration of prediction, the rate threshold of the micro-seismic signal converges from 0.00039 x 10-6 to 0.00031 x 10-6 m/month, the effective duration of prediction is approximately 6-10 months, and R also converges from 0.29 to 0.31. By comparing the results of three gPhone gravity stations in Guangxi, we found that the increase of short-term VD before the Debao earthquake was related to the enhancement of the DF micro-seismic signal excited by the typhoon. When the typhoon track was perpendicular to the coastline of China, the possibility of an earthquake occurring was increased. This study provides evidence and reference for the future occurrence period of earthquakes above MS4.0 in western Guangxi. (c) 2023 Editorial office of Geodesy and Geodynamics. Publishing services by Elsevier B.V. on behalf of KeAi Communications Co. Ltd. This is an open access article under the CC BY-NC-ND license (http:// creativecommons.org/licenses/by-nc-nd/4.0/).

Global and regional ocean tide models are used to analyze the gravity effect of ocean tidal loading (OTL) for gravity stations in East China. The accuracies of OTL correction results for 21 gravity stations in East China are evaluated. The global ocean tide model is the most effective for the OTL correction of inland gravity stations (up to 90%) but is less effective for coastal gravity stations (only 60%). Considering regional ocean tide models, the applicability of OTL correction increased to 80% in coastal gravity stations. Based on the root sum square ( RSS ) method, among 16 combination models, the optimal combination model for OTL correction is the global model FES2014b by combing the regional model OSU.Chinasea.2010 (F14O). The RSS , which has reached 7.1 nms −2 , is the minimum of the 16 combination models. Simulating with the F14O in the China Sea and adjacent areas, the gravity amplitude of the OTL is about 10 nms −2 in inland areas and > 50 nms −2 along the coastline. Especially in Southeastern China coastal areas and the southwestern coastal areas of the Korean Peninsula, the gravity amplitude of the OTL reaches about 80 nms −2 . Moreover, the OTL changes drastically possibly owing to coastal topography. The results of this study provide a reference for selecting ocean tide models for high-precision analysis of continuous gravity observations in East China.

针对中国大陆重力站主要装备的gPhone相对重力仪(约62套)由于缺乏标定,限制其高精度重力数据的科学应用的问题,收集了中国大陆12站同址FG5绝对重力观测与同时段gPhone观测的资料,提出了基于DDW-NHi全球潮汐模型约束的FG5绝对比测标定gPhone重力仪的方法,并与gPhone重力仪出厂格值法、理论固体潮标定法进行比较,讨论未来绝对重力标定的策略.研究结果表明:利用同址绝对观测时长26-64h资料标定gPhone重力仪,格值系数的相对误差为±0.001 3～±0.003 8;标定后各站重力残余振幅≤1×10-8m/s2,达到gPhone重力仪标称精度,优于出厂格值和理论固体潮标定结果;标定后经固体潮、气压负荷潮改正的重力残差振幅与中国大陆海潮负荷规律相符.

文中基于滇西地震实验场1986—2014年间近30a的流动重力观测资料,研究了该地区重力场的长期变化背景.结果表明,重力场长期变化背景以负变化为主,年平均变化率约为-1.24×10-8 m/s2;空间分布上,重力场变化的剧烈程度与断裂带分布和历史强震活动存在密切关联,红河断裂北段、龙蟠-乔后断裂对本地区的重力场变化和地震活动分布具有明显的边界作用.结合地壳垂直形变、地壳结构和区域动力学背景对重力场变化机理进行分析,重力场整体负变化趋势可能反映下地壳物质流引起的地表隆升和地壳增厚,而重力场变化空间分布的细节则与区域动力学背景下具体断裂带的活动特性以及相关的局部性物质分布变化有关.

2019-12-26应城MS4.9地震前,襄阳重力台记录到第二类(double frequency,DF)地脉动信号持续增强异常.对比全球能量辐射模型(ASSM)及西太平洋台风数据发现,震前10 h左右的DF地脉动增强及优势频率增大的异常与西太平洋Phanfone台风靠近中国大陆这一远场信号源关系较弱,与本地未知近场同源同频信号有关.结合恩施重力台观测分析认为,该异常信号不属于应城地震前的慢地震事件.此外研究发现,长江中游巴东-秭归段和襄樊-广济断裂及其邻近区域5次MS 4.0以上地震中的4次都与七曜山-金佛山断裂附近发生的MS4.5～5.0地震呈成组活动,时间间隔为0.5～1 a,且发震时间都在DF地脉动信号的高噪声水平时段内(10月～次年3月).当恩施-襄阳DF地脉动信号基线的月中位数和众数值的差异持续4个月增加或处于高值时,研究区发生MS 4.0以上地震的可能性增加.对震前DF地脉动信号异常特征的总结可为预测未来长江中游巴东-秭归段和襄樊-广济断裂及其邻近区域MS 4.0以上地震的发生时段提供经验指标.

利用重力台网进行台风激发信号的源区定位研究不仅有助于提高台风监测能力,而且可从台风激发信号中区分出震前与震源有关的信号,促进地震预测研究.以2019年第18号台风米娜(MITAG)为研究对象,基于福建省重力台网观测的1 Hz采样的固体潮观测数据,利用噪声互相关函数的信噪比(signal-to-noise ra-tio,SNR)和归一化噪声能量流方法分析数据质量和微震源区方位,使用SNR≥25的Rayleigh波互相关信号走时作为定位数据,进行台风4个时段的定位研究.结果表明,在MITAG台风靠近中国大陆的过程中,定位区域能够覆盖台风中心所在位置;地震背景噪声能量辐射模型的微震垂直位移极值区域也和台风靠近中国大陆过程时段一致;通过人工剔除高速波群的互相关信号后,定位区域也能覆盖到转向远离大陆过程时段的台风轨迹.福建省重力台网对台风的追踪提供一类新的数据和方法.

Abstract Global and regional ocean tidal models were used to analyze the gravity effects of ocean tidal loading on continuous gravity observations in eastern China. The accuracies of tidal loading gravity correction results for 21 gPhone and superconducting gravity stations were evaluated. The global ocean tidal model was most effective for gravity correction at inland stations (up to 90%), but less effective at coastal stations (only 60%). Taking into account regional ocean tidal models, the effectiveness of tidal loading correction increased to 80%, and the root sum square of the residual gravity series was 0.7450 ~ 0.9733\({\times 10}^{-8}\text{m}{\text{s}}^{-2}\). The best tidal loading gravity correction was obtained by combing the global FES2004 model and regional OSU.chinasea.2010 model (root sum square of 0.7450\({\times 10}^{-8}\text{m}{\text{s}}^{-2}\)). Using this combination, the tidal loading gravity amplitude in the China Sea and adjacent areas was calculated; tidal loading gravity was. Very low gravity effects were obtained inland and for island interiors; however, tide loading gravity was relatively larger along the coast, especially the southeast coast and Bohai Bay. Moreover, the amplitude changed drastically possibly owing to offshore topography. Our results provide a reference for selecting ocean tidal models for high-precision analysis of continuous gravity observations in China.

为研究重力时变因素对流动重力网数据处理结果的影响,利用动态和静态2种平差方法对南北地震带南段流动重力观测数据进行处理,并对2种方法的重力变化结果进行对比分析.结果表明:1)重力时变因素会导致静态平差方法计算的重力变化结果存在误差,对0.5a和1a时间尺度下的重力变化具有较为明显的影响,但对2a以上时间尺度下的重力变化影响较小,因此计算0.5a和1a时间尺度下的重力变化时宜采用动态平差方法;2)研究区内九寨沟7.0级、长宁6.0级和漾濞6.4级地震的发震地点与重力变化零值线具有较好的对应关系,重力变化图像可反映3次地震的发震背景.

古登堡-里克特频度-震级关系式中的b值常被用作估算区域应力大小的一个重要指标,对于评估地震发生概率起着至关重要的作用.北京时间2021-05-22T02:04:11青海省玛多县附近发生Mw 7.4地震,此次地震发生在巴颜喀拉块体内部,东昆仑断裂以南的次级断裂昆仑山口-江错断裂上.为了揭示这次玛多地震之前震源区的孕震环境和震后余震的演化,利用中国地震台网中心提供的2009-01-01-2021-05-20地震目录,对玛多地震发震前后的b值分布和变化进行了研究.研究发现,在2021年5月22日之前,玛多地震主震区b值最低,表明震源区存在明显的应力积累;从近十年震源区b值的时间序列来看,b值也呈现下降趋势,该发现可以作为今后判定块体内部大地震主震临近的重要依据.利用震后的余震序列计算了断层周边的b值变化,发现早期的b值变化对后期余震的发生位置预测也具有一定的指导作用.

为评估全球潮汐模型在我国潮汐改正中的适用性,本文首先对10个重力站2016—2018年的观测数据进行了精度评定,而后基于均方根、和方根、纬度依赖关系以及重力残差等指标对7个全球潮汐模型进行了精度评定.结果表明:10个重力站的一些评价指标达到甚至超越了早期超导重力仪,例如M2波潮汐因子的中误差普遍小于0.00070,其中最高精度约为0.00014,5个主要潮波的稳定度均≤0.0015.在10个观测模型和7个全球潮汐模型中,DDW-NHi和M2001模型考虑了地球扁率的影响,基于这两个模型计算的和方根较其它模型所得的和方根均小,约为0.288×10-8 m/s2.基于最高精度的乌什站数据对Molodensky,DDW-NHi,M2001与观测模型的改正精度的对比显示,DDW-NHi模型改正计算的重力残差(±0.4×10-8—±1.0×10-8 m/s2)不及观测模型(±0.1×10-8—±0.5×10-8 m/s2),但依然优于M2001模型(±0.7×10-8—±1.4×10-8 m/s2),且DDW-NHi模型改正获得的残差比传统的Molodensky模型所得残差(±0.5×10-8—±1.5×10-8 m/s2)小1×10-8—2×10-8 m/s2.

One important procedure in gravity data processing is making tidal corrections. Sound tidal corrections rely on accurate tidal gravimetric factors. The present study selects data from 12 gPhone gravimeter stations and three superconducting gravimeter stations for the period between 2009 and 2015, distributed across mainland China. Based on these data, the distribution of M2 tidal gravimetric factors over China is obtained. We also estimate the corresponding theoretical values of the M2 wave provided by the DDW99 solid Earth tide model (Dehant et al. in J Geophys Re Solid Earth 104:1035–1058, 1999) and the CSR4.0 ocean tide model (Eanes and Bettadpur in The CSR3. 0 global ocean tide model: diurnal and semi-diurnal ocean tides from TOPEX/POSEIDON altimetry, The University of Texas Center for Space Research, 1996). The results suggest that the measurements and theoretical values of the M2 wave are similar, with an average misfit no greater than 0.6% for most regions of China’s mainland, although the misfit is relatively large, about 1.1%, in northeast China. According to the latest three-dimensional tidal theory and the correction effects on the M2 gravimetric factors at Lhasa, Lijiang, and Wuhan, where the three superconducting gravimeters are located, we select the best-fitting three-dimensional Earth model, GyPSuM (Simmons et al. in J Geophys Res Solid Earth 115:B12, 2010), for mainland China. The theoretical values of the tidal gravimetric factors while considering three-dimensional inhomogeneities are calculated. The results show that the variation in gravimetric factors caused by lateral inhomogeneity across China is from −0.07 to 0.09%.

潮汐变化空间分布可用于地球不同位置受外力响应及地球形状、地表变形的相关研究.受观测技术、仪器数量和观测精度等制约,中国大陆重力潮汐观测直到21世纪初才得到较大改善和发展.利用2015-2017年中国大陆运行较好的51个重力站潮汐观测数据,采用国际标准潮汐处理方法和软件,分析计算了中国大陆主要潮波潮汐因子的空间分布,同时,结合1′×1′的全球地形模型(ETOPO1)和全球重力场模型(WGM2012)讨论了中国大陆东西和南北向2个潮汐剖面的构造物理特征.研究结果表明:①90％以上重力站M2波潮汐因子中误差优于0.001,这已和20世纪80～90年代的超导重力仪的观测精度相当;沿海台站的O1和K1波潮汐因子大于其他地区,经Nao99b和Nao99jb海潮模型检验认为是海潮负荷引起的.②沿狮泉河—玉树—松潘—黄梅—上海佘山的东西向M2波潮汐剖面显示,当海拔高程差异超过4500m、布格重力异常差异600×10-5m/s2时,重力站间M2波潮汐因子差异可达2％,且和高程呈正相关特征.③沿孟连—西昌—银川—乌加河的南北向M2波潮汐剖面站间潮汐因子差异为1.0％～1.5％.④重力站潮汐因子和高程的相关性分析表明,内陆站M2、O1波相关系数超过40％具有正相关特征.上述结果可为中国大陆地壳结构横向不均匀性和动力变形响应研究提供参考.

微震信号主要来源于海浪运动中能量从海洋传递到固体地球时的耦合作用.台风期间强烈的海浪运动易于激发微震信号.本文基于东南沿海地区2016年的连续重力观测数据,系统研究西太平洋的9次台风和中国台湾高雄MS 6.7地震前后重力微震信号的时频特征,并与实测海洋浮标系统的波高和风速开展了相关性分析.结果 表明:(1)台风引起的剧烈海浪运动使东南沿海重力仪记录到的地脉动信号显著增强,重力地脉动信号随着台风进程而演化,其时频特征谱优势频段主要分布在0.1 ～0.3 Hz.短周期双频微震信号(0.2～0.3 Hz)能量最高,长周期双频微震信号(0.1 ～0.15 Hz)频段次之,单频微震(0.05 Hz)频段的能量最弱.台风持续期间,短周期双频微震信号频段的归一化振幅呈现出与台风对应的显著增强变化.沿海的福州台、厦门台和漳州台的地脉动信号的振幅均高于内陆台站龙岩台的振幅.(2)0.15 Hz长周期双频微震信号的归一化振幅高值与登陆和临近福建的"莫兰蒂"、"海马"等4次台风相关性好,推测该频段与有效的台风激发距离和强度有关.在台风风力13级以上,且台风中心距离台站小于300 km内,易于激发长周期双频微震信号.(3)福州台和厦门台的重力地脉动归一化振幅与马祖和金门浮标实测的风速相关性较低,平均相关系数为0.3;地脉动归一化振幅与实测有效波高的相关性较高,平均相关系数为0.6.重力地脉动信号各频段归一化振幅与波浪有效波高的时间演化近于同步,且互相关峰皆无明显的时间延迟.福州和厦门重力记录到的地脉动信号主要来源于附近的沿海海域.(4)对2016年高雄MS 6.7地震的研究表明,震前两周存在0.15 ～0.2 Hz频段的重力扰动异常,排除台风和降雨的干扰影响.对该组震前扰动异常的解释有赖于更多观测手段和更高分辨率数据的分析.本文研究结果对于认识重力微震信号的规律特征和来源具有较好的参考意义,也有助于进一步科学识别重力微震信号中的地震前兆异常.

对中国大陆7次强震前出现的典型重力场变化图像(梯度带和四象限)及其量化参数进行总结.结果表明,目前采用的地震预测指标具有一定的不确定性,与测网观测时段、测点空间分布、变化幅值空间差异等具有密切关系;芦山地震前潮汐因子异常空间范围是流动重力典型变化范围的近10倍,可能与连续重力观测站的精度比流动重力联测高1个数量级有关.基于闭锁剪力模式提出利用典型重力变化图像进行地震数值预测的方法,强震前在孕震源存在的双力偶闭锁剪力的持续作用下,走滑型力偶会在地表引起四象限重力变化,倾滑型力偶会在地表引起二象限(梯度带)重力变化.预测回溯算例实验结果初步表明,该方法对走滑型和倾滑型地震的震级预测较为有效,同时可给出未来地震的地点和类型.

同震重力变化可为位错模型的检验和约束提供新数据.文中利用指数函数和阶跃函数法分析了玛多MS 7.4地震震中距≤800km的5个重力台的同震重力信号.结果显示:观测和位错模型模拟结果的方向一致性好,只是量级存在差异.通过对同震重力变化精度的讨论,同震重力变化和GNSS垂直位移的比较,九寨沟MS7.0、玛多MS7.4同震重力变化空间分布的分析,以及漾濞MS6.4地震对同震重力变化影响的改正,分析认为:震中距为175km的玛沁台记录到(2.9～4.0)×10-8m·s-2的同震重力变化;震中距为763km的中甸台在改正了漾濞地震的影响后记录到1.09×10-8m·s-2的同震重力变化;松潘台记录的9.1×10-8m·s-2的重力变化信号中应包含其他因素的影响;林芝台的负变化规律和位错模型模拟结果方向一致.综合文中的观测结果认为,玛多MS 7.4地震能够在175～800km的远场范围内产生约(0.5～4.0)×10-8m·s-2的同震重力变化信号.该结果可为未来中强地震远场产生的同震重力变化量级的判定提供参考.

In this paper, the flexural isostasy and gravity variations before the 2021 Madoi M(s)7. 4 earthquake were studied using the EIGEN6C4 Bouguer gravity anomalies, SIO V15. 1 topography model and the repeated gravimetry data. Firstly, based on the lithospheric flexural isostatic model, combining with Bouguer gravity anomalies and topography data, the effective elastic thickness (T-e) and the flexural isostatic gravity anomalies of the lithosphere in the epicenter and its surrounding area (northeastern Qinghai-Tibet Plateau) were calculated using the finite difference method. The results show that T-e ranges from 0 to 100 km in the northeastern Qinghai-Tibet Plateau, with obvious lateral changes and close relationship with block tectonic structures. To the north of the Bayan Har block, T-e of the Qaidam block is as high as 50 similar to 80 km, to the south, T-e of the Qiangtang block is larger than 20 km, with local high values larger than 30 km in the south of Wudaoliang and larger than 40 km around Yushu-Dege area. T-e of the Bayan Har block is 0 similar to 20 km, which is smaller than that of the north and south blocks, and it is more prone to deformation. Therefore, the mass in the Bayan Har block moves eastward under the north and south holding, and it is the primary area of eastward material flow in the central part of the Qinghai-Tibet Plateau. Earthquakes are prone to occur in the transition zones of lithospheric strength change (T, gradient zones) , as well as on the faults where T-e is low. The Madoi M(s)7. 4 earthquake occurred in the area with low T-e inside the Bayan Har block, with an effective elastic thickness of about 15 km near the epicenter. The analysis of repeated gravimetry data before the earthquake shows that the 3 similar to 5 years' accumulated gravity variations since 2015 present a regional change characteristic of negative-positive-negative from west to east, and a high gradient zone of gravity variation perpendicular to the fault zone is formed with the epicenter as the boundary, which mainly reflects the deep tectonic movement situation in the process of material flow from the Qinghai-Tibet Plateau to east before the earthquake. The gravity variations since 2018 is mainly characterized by a weak regional change from positive in the west to negative in the east around the epicenter, which shows that the epicenter area has been in the "solidification" state of high stress and strain, and the earthquake occurred at the turning point of the zero value line of gravity variations.