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.

High-precision time-varying terrestrial absolute gravity observations provide a powerful tool for investigating mass redistribution processes within the Earth’s interior and at its surface. The southeastern margin of the Tibetan Plateau is a tectonically active region with frequent strong earthquakes, making accurate interpretation of local gravity observations critically important for earthquake prevention and disaster mitigation. Based on four epochs of absolute gravity measurements acquired using FG5(X) gravimeters at the Dongchuan station from 2017 to 2022, combined with co-located continuous GNSS vertical deformation data, a GLDAS Noah Land Surface Model, high-resolution remote sensing imagery, and forward numerical modeling, we performed quantitative corrections for crustal deformation and hydrological effects and analyzed the residual gravity variations. The results show that gravity change at the Dongchuan station exhibited an overall increasing trend with a maximum amplitude of 8.2 μGal during 2017–2022. While the 2017–2019 gravity changes were consistent with the combined effect of crustal vertical deformation and hydrological loading within uncertainty, a positive residual anomaly of several microGal remained after 2019, which was attributed to mass redistribution caused by nearby anthropogenic activities. This study confirms that the 2017–2022 Dongchuan observations meet the requirements for milliGal-level static gravity field research, with the 2017–2019 data suitable for time-varying gravity studies, while the post-2019 data require that gravity variations induced by anthropogenic activities in the vicinity of the station be accounted for when applied to such studies. Additionally, time-series high-resolution remote sensing can effectively identify hundred-meter-scale gravity disturbance sources near observatories, providing valuable support for gravity data interpretation and quality control.

Traditional seafloor mapping relies on shipborne soundings which have limited spatial coverage. The Surface Water and Ocean Topography (SWOT) wide-swath altimetry satellite holds the potential for predicting more detailed seafloor topography. In this study, we integrate SWOT gravity data with single-beam shipborne depths to construct seafloor topography models in the Northwestern Pacific using the deep neural network (DNN) method. Compared to shipborne depth checkpoints, the root mean square (RMS) error of the differences between topography model predicted by DNN method and shipborne depths is approximately 97.5 m, improving by 19.5 per cent and 9.9 per cent compared to the gravity-geologic (GGM) method and the Smith and Sandwell (SAS) method respectively. Compared to traditional data, the integration of SWOT gravity data universally enhances prediction accuracy. Furthermore, the DNN method effectively demonstrates superior capability in balancing the characterization of overall structures with the retention of authentic topography features, which we demonstrated in the Mariana region of the NW Pacific Ocean. However, limited by spatial heterogeneity and physical mechanisms, accurate prediction of such complex, fine-scale topography using gravity data remains a significant challenge.

Coseismic gravity changes provide significant information for the study of the mechanisms of large earthquakes and for developing fault models (Sun, 2012). In this research, coseismic gravity changes of the 2008 Ms8.0 Wenchuan earthquake in China were studied by using gravity observation data and simulation based on a fault model.Firstly, a fine processing of relative and absolute gravity data from the Longmenshan Gravimetric Network was carried out and observed gravity change of 22 stations near this earthquake were obtained; Secondly ,simulation of coseismic gravity changes was conducted based on half-space dislocation theory using the fault model obtained by Wang et al(2008) through inversion with multiple types of geodetic survey data, including GPS, INSAR, and leveling, and the results were compared with the observations..It was found that the observed and simulated results are basically consistent, showing that the significant changes are mainly concentrated in the near-rupture zone in the hanging wall of the Yingxiu–Beichuan fault and that the changes decrease rapidly away from the rupture zone. The changes exhibit a positive to negative trend from east to west in the footwall of the Yingxiu–Beichuan fault and have a distribution characterized by alternate positive and negative changes in the hanging wall of the fault. This demonstrates the reliability of the observed results and the reasonableness of the fault model used in this paper.In the near-rupture zone on the west and east sides of the Yingxiu–Beichuan fault, there are still some differences between the observed and simulated results. The trends in the spatial distribution of these differences exhibit a deviation similar to “phase delay”; in other words, an observed result deviates from the corresponding simulated result in terms of spatial position, which is speculated to be caused by errors in the geometric parameters and in the slip distribution of the fault model. After the slip distribution of the Pengguan fault model was modified based on the actual surface rupture distribution, the simulated result at the Hongjiawan station near the eastern boundary of the fault model showed greater consistency with the observed result. This indicates that the observed gravity change results in this paper can provide an important reference for further detailed study of the fault model. Fig1.Schematic of the Chengdu Gravimetric Network Fig2.Spatial distribution of observed gravity changes and simulated results

High precision surface gravity observation is one of the key means to study the internal deformation and material transport of the Earth. In the past decade, with the rapid development of modern precision geodetic observation technologies and the accumulation of high-precision gravity observation data on the surface, the application and research of absolute gravity observation in China's earthquake prevention and disaster reduction undertakings and the field of earth science have been deepened and expanded. This article mainly summarizes the application and research progress of absolute gravity observation in geodesy and geophysics in China, including the development of absolute gravity observation technologies (absolute gravity observation network, absolute gravity data processing), as well as the research progress of absolute gravity in earthquake monitoring (earthquake monitoring and prediction, calibration, and comparative observations of seismic gravity instruments) and geodynamics (crustal structural deformation, surface material migration, establishment and evaluation of gravity field models). Finally, some suggestions are proposed for development trends and application research directions of absolute gravity observation in terms of spatial resolution, gravity measurement network design, and new gravity observation technologies. With the gradual maturation of various types of independently developed absolute gravimeters in China, it is believed that absolute gravity observation will bring broader opportunities and prospects in application and research.

We propose the establishment of an observational network comprising micro gravitometers across East Asia including, but not limited to Republic of Korea, Japan, Taiwan, and the Chinese mainland. The network will generate a parallel observation belt within the seismogenic zone that connects the Japan Trench, Ryuku Trenches, and Nankai Through, both constituent components of the Ring of Fire, for the detection of slight changes in micro-gravity for analyzing earthquakes of different magnitudes with different sources and depths. We will establish a data hub for sharing data, managing combined data format, and distributing computing resources for conducting collaborative research. In addition, the network measurement of micro-gravity can be used for searching the dark matter candidate inside Earth. The presentation demonstrates various science cases that could be undertaken by implementing a network of GWR Instruments Inc.’s superconducting gravimeters and a data hub within the East Asian region.

Based on the 107 earthquakes of M-s >= 4. 0 collected, the statistical characteristics of the gravity changes anomaly before earthquakes in Chinese continent were studied. The statistical relationship between earthquake magnitude M-s and the gravity changes and the nature of the earthquake was explored. Reference indicators for the scale parameter S, magnitude parameter G, and time parameter T of gravity changes for M(s)5. 0, M(s)6. 0, M(s)7. 0, and M(s)8. 0 earthquakes have been given. The gravity changes before thrust, strike-slip, and normal earthquakes were compared and analyzed. Furthermore, by integrating the hypothesis of fluid-matter migration and the results of petrophysical experiments, the physical mechanisms of gravity changes before earthquakes and their connection with the meta-instability stage and the energy for earthquake gestation were discussed. The main conclusions are: (1) The relationship between gravity change parameters before earthquakes and earthquake magnitude appears to be nonlinear across all studied cases. Specifically, for earthquakes of magnitudes M(s)5. 0, M(s)6. 0, M(s)7. 0, and M(s)8. 0, the reference indicators for scale parameter S are 67, 111, 185, and 305 km; for magnitude parameter G, they are 49, 67, 92, and 125 mu Gal; and for time parameter T, they are 1. 6 year, 2. 5 year, 3. 7 year, and 5. 2 year, respectively. (2) The type of earthquake has some influence on the gravity changes before the earthquake, and the difference is especially obvious for earthquakes with M-s >= 7. 0. In terms of the scale parameter S of gravity change, the largest is for strike-slip earthquakes with M-s <= 6. 0, followed by normal earthquakes and then thrust earthquakes; thrust earthquakes are the largest with M-s>7. 0, followed by strike-slip earthquakes. In terms of the magnitude parameter G of gravity change, for magnitude M-s<7. 0, slip -type earthquakes are the largest, with thrust and normal earthquakes slightly lower; for magnitude M-s >= 7. 0, thrust earthquakes are the largest, followed by strike-slip earthquakes. In terms of the time parameter T of gravity change, normal earthquakes may correspond to longer times, followed by thrust earthquakes, and strike-slip earthquakes have the shortest times. (3) The possible physical mechanism of the gravity change before earthquakes are as follows: during the late stage of earthquake development or the meta-instability stage, the accumulated stress and strain in the surrounding area of the epicenter reach their peak, leading to the increase, expansion, and connection of rock fractures, which causes deep mantle material with rheological properties to migrate towards the crust, while the pre-existing fluid in the crust undergoes large-scale migration due to unequal stress distribution, ultimately causing a response in the surface gravity field. (4) The increase in pressure on the fault plane of a thrust earthquake will increase the frictional strength of the fault and inhibit rupture, leading to a higher parameter of gravity change. The increase in tension on the fault plane of a normal earthquake reduces the frictional strength of the fault and promotes rupture, resulting in a smaller parameter of gravity change. The longer time of gravity change may be related to the weaker driving force of tensile tectonics in mainland China. (5) The current mobile gravity measurement is constrained by the spatial and temporal density (point spacing of >= 30 km, time scale of >= 0. 5 year), so that the gravity change before earthquakes of M-s < 5. 0 are generally not observed. Earthquake prediction based on gravity change anomalies mainly target earthquakes of M-s >= 5. 0, and the larger the magnitude MS, the better the prediction efficacy.

High-precision repeated absolute gravity observations conducted at the Luzhou observatory provide valuable insights into the processes of mass redistribution in the station's vicinity. In this study, we analyze four campaigns absolute measurements from two absolute gravimeters, FG5X-255 and FG5X-259, observed at the Luzhou gravity observatory and find a decrease in the gravity value of (− 93.3 ± 3.1) × 10 –8 m·s −2 from October 2020 to July 2022. By subtracting the contributions of vertical deformation, hydrological change, earthquake, and offset between instruments from the observation results, we derive a residual gravity change of (− 92.7 ± 4.1) × 10 –8 m·s −2 . Further analysis of field site photos and satellite images reveals that excavation related to the construction of a building near the Luzhou station is responsible for the observed gravity decrease. We use the load theory to calculate the gravity change at the Luzhou station due to the mass removal in the construction area and find that this factor could produce a gravity decrease consistent with the magnitude of the residual gravity change. Our results demonstrate that localized sources of mass redistribution, such as excavation at construction sites, can cause gravity variations exceeding 90 × 10 –8 m·s −2 nearby. Overall, our study highlights the importance of considering local mass redistribution when interpreting gravity variations.

Historical single-beam depths provide crucial information of the seafloor topography. This study gathers 119 million data points from 5464 global single-beam track-lines provided by the NCEI. The accuracy of the single-beam depths was evaluated by analyzing crossover errors and comparison with the GEBCO_2023 model. The results indicate that the MAD of the external crossover error in the global single-beam track-lines was 44.4 m, with the highest quality in the Atlantic Ocean (34.1 m) and the lowest quality in the Indian Ocean (117.9 m). The mean difference between global single-beam depths and the GEBCO_2023 model was -54.1 m, with a STD of 260.9 m. Data collected before 1970 generally exhibited lower quality. There was at least one error in 2623 track-lines (48% of the total data). Furthermore, 50 track-lines were affected by scale factor bias and traveling time errors. We developed a visualizing window tool to identify and correct these errors. The error-corrected single-beam dataset was obtained by eliminating individual error points, modifying the scale factor, and correcting the traveling time error. The mean difference between the error-corrected dataset and the GEBCO_2023 model is 6.8 m, with a STD of 68.5 m. This indicates a notable enhancement in the overall accuracy.

文中推导并给出了基于非格网分布的起伏面扰动重力或重力异常解算区域扰动重力梯度场模型的数值计算公式.基于澳大利亚 West Arnhem Land 地区的格网重力数据,以频谱域(二维快速傅里叶变换)解算的扰动重力梯度全张量作为"基准值",然后利用基于推导公式的最小二乘配置方法(LSC)对相同区域非规则范围的重力数据进行扰动重力梯度模型解算,将结果作为"评估值".对比"基准值"与"评估值"之差,研究发现:1)基于推导公式的最小二乘配置方法解算得到的扰动重力梯度值与频谱域方法得到扰动梯度"基准值"各分量在空间形变变化上是一致的;2)统计扰动重力梯度各分量的差值 ΔδΓfft-lscxx、ΔδΓfft-lscxy、ΔδΓfft-lscxz、ΔδΓfft-lscyy、ΔδΓfft-lscyz 和 ΔΓfft-lsczz,"基准值"与"评估值"差值的标准差分别为 5.54E、5.30E、1.85E、6.55E、2.09E 和 9.67E(1 E=1×10-9s-2),远低于国际上实测重力梯度与解算模型差值的研究结果.最后,基于云南地区实测地表差分重力值,文中首次给出了该区域半波长约 20km的重力梯度场年际变化模型.文中的思路和方法提高了广泛分布的重力数据(主要为重力异常和扰动重力)的使用效率,可为地球物理学、地质学研究更好地理解和解释重力数据、重力梯度数据及其与场源的关系提供数据基础.

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.

Using the gravity observation data of Mulanshan short gravity baseline field in 2018 and 2022,we established a high-precision short gravity baseline field of Mulanshan based on the relative gravity joint measurement method under the control of absolute gravity.We also analyzed and discussed the accurate calibration of the monomial coefficient of the relative gravimeter during the construction of the gravity short baseline field,the distribution of gravity values in the gravity baseline field of Mulanshan and the contribution of various environmental factors in the gravity variation results,these results show that:（1） Maximum gravity segment difference of Mulanshan calibration baseline is 102.176mGal from G01 to G03 stations,and the average accuracy of gravity value of each measuring station reaches4.8μGal.The geological structure of the Mulanshan baseline is stable,and the gravity change of measuring stations is not obvious.From 2018 to 2022,the gravity variation range of measuring stations was 5.9～12.8μGal,with an average of 9.5μGal,and the average uncertainty was±5.7μGal.The gravity field mainly showed a positive change.The variation range of gravity in each measurement section is-4.8～6.9μGal,with an average of （1.8±8.6）μGal.The change of the surrounding environment has a certain impact on the gravity field,and the contribution of the new buildings near the G01 and G02 to the gravity change is 3.6μGal and-0.51μGal,respectively.These gravity changes of measuring stations in the IOS and Mulanshan baseline caused by vertical surface movement are（2.17±0.44）μGal and （1.67±0.45）μGal.The gravity effect caused by the change of surface water storage is（1.07±0.84）μGal,which cannot be ignored.Compared with observation results,the gravity change of each measuring station and section after correction is reduced,and the average gravity change values are reduced by 38.2%and 50.8%,respectively.The corrected gravity change results are more accurate.Due to the cumulative effect of errors in the correction process,the uncertainty of gravity change results after correction increases accordingly,and the uncertainty of gravity change results of measuring station and measuring section increases by 2.5%and 2.8%compared with observation results,respectively.Combined with the gravity change results of the measuring station and the measuring section,we can effectively extract abnormal information in gravity dynamic change results.（2） There are differences in monomial coefficients of different gravity sections of the relative gravimeter.The results of CG-6 and CG-5 relative gravimeters are relatively consistent,and there is no systematic deviation between the two gravimeters.The difference in the monomial coefficient between the Wuhan-Yichang section（sub-section） and the Wuhan-Lücongpo section（total section） is4.809‰，which has a great influence on the gravity observation results.The monomial coefficient needs to be accurately measured.The difference of the monomial coefficient in the sub-section is negatively correlated with the proportion of the gravity segment difference in the sub-section to the total section;the monomial coefficient of the total section is a weighted average result of each subsection,and the proportion of gravity segment difference in sub-section to total section is the corresponding weight factor.Accurate calibration of the monomial coefficient of the relative gravimeter is a technical guarantee to obtaining high-precision gravity observation results.The gravity segment difference of sub-segments cannot cover the gravity range of the measurement area due to smaller segment difference,which will lead to the extrapolation of the monomial coefficient,so it cannot effectively calibrate the monomial coefficient of the relative gravimeter applicable to the whole measurement area.The total section can cover the gravity range of the measurement area,and the monomial coefficient is the ratio between the segment difference measured by the relative gravimeter and the known segment difference,and its calibration accuracy is inversely proportional to the gravity segment difference,so when using the total section as a reference for calibration of the monomial coefficient of the relative gravimeter,accuracy of the calibration can be guaranteed and precision of the calibration can be improved,so calibration result of the monomial coefficient using the total section is more accurate.The existing widely used relative gravimeters （such as LCR,CG-5,BURRIS,CG-6,and so on） have time-varying characteristics of the monomial coefficient,weakening the errors caused by changes of the monomial coefficient is essential to improve the accuracy of observations,and corresponding calibration is required before each period of gravity observation.The monomial coefficient of the relative gravimeters needs to be calibrated using a large segment difference,and the segment difference（or the accumulated segment difference） should be greater than300mGal.

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.

本文利用卫星重力数据和海底地形数据对大塔穆火山开展详细的重力导纳分析.结果显示大塔穆火山的岩石圈有效弹性厚度是1～3 km,指示火山形成于洋中脊之上,符合低重力异常和洋中脊三联点的构造背景.Airy均衡模型和岩石圈挠曲均衡模型推算的大塔穆火山的平均地壳厚度是11～17 km,最厚处拥有一个约30 km的地壳根,与实际地震观测结果基本一致.大塔穆火山的超厚洋壳不同于正常洋中脊,目前地幔柱与洋中脊相互作用是比较合理的成因模式.研究还发现大塔穆火山底下存在一个质量缺失的低密度区,这个区域可能是残留岩浆房造成的结果,与火山中心的地球化学特征、地震波速异常以及广泛的后期火山活动相吻合.另外,这个低密度区提供浮力支撑火山中心隆起,可能导致火山侧翼因差异性沉降而产生正断层.

The marine gravity field model is mainly derived from nadir satellite altimetry measurements. However, the accuracy of the east component of the vertical deflection is significantly lower than that of the north component in most areas due to the orbital inclination of altimetry satellites. As a novel altimetry technique, wide-swath altimeters are expected to simultaneously obtain high-precision and high-resolution two-dimensional sea surface height measurements and hence to improve the accuracy and resolution of the recovered marine gravity field model. Here, taking the Surface Water and Ocean Topography (SWOT) wide-swath altimeter mission as an example, based on the proposed nadir ground tracks and swath width, one cycle of SWOT sea surface height measurements is simulated and compared with one year of the simulated sea surface height measurements from the nadir altimeter missions of Jason-1/GM (Geodetic Mission), Cryosat-2/LRM (Low Rate Mode) and SARAL/GM. Then, the vertical deflections are determined in the South China Sea and part of the Indian Ocean. Compared with the EGM2008 gravity field model, the vertical deflections determined by one cycle of SWOT data are better than the results determined by the combined dataset of Jason-1/GM, Cryosat-2/LRM and SARAL/GM data and can significantly improve the accuracy of east vertical deflection. It is determined that the SWOT random and systematic errors have certain effects on the accuracy of the vertical deflection, but these can be reduced by filtering. In addition, under the premise of the expected accuracy and spatial resolution of the SWOT mission, vertical deflections with grid spacing smaller than 1 arcmin and comparable accuracy could be derived.

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.

长期的重力变化和地壳形变观测是研究地下物质运动的重要手段.基于武汉九峰地震台2013-2020年的绝对重力和全球卫星导航系统(global navigation satellite system,GNSS)观测数据,计算了长期的重力与地壳垂直形变的变化趋势,并以1年、2年和3年的时间间隔分段,进行线性趋势拟合,分别获得不同时间段的绝对重力年变化率、地壳垂直形变速率以及对应的比值.研究结果表明,武汉九峰地震台长期的重力年变化率为0.479 9μGal/a,地壳垂直形变速率为-1.2 mm/a,两者的比值为-0.399 9 μGal/mm,与理论值存在一定的偏差,可能与该区域的地下水活动有关.将不同时间段的重力变化与地壳垂直形变的数据展布在一张图中,发现数据点离散分布在不同区域,由此可初步判断地下物质运动过程,为区域动力学机制解释提供参考.

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.