离散时变重力数据的可视化、指标量定义与解释

The index definition,interpretation and visualization of discrete time-variable gravity data

针对流动重力观测获得的数据成果特点,提出一种基于流动重力段差变化的时变重力数据可视化方法,并定义了两个指标量G值和C值,用以评价区域性重力场变化的显著性程度.在此基础上,应用该方法处理和分析了首都圈地区的流动重力数据.结果表明:与传统采用等值线方式来刻画时变重力场特征不同,该方法更能突出发生变化的重力测点位置、测量误差及其变化的显著性程度,可为研究与地震孕育、发生过程有关的重力场变化提供更多的定量依据.

The campaigned gravity survey is a sort of time-lapse terrestrial gravity survey,which generally means the gravity observed repeatedly at a fixed station with the same routes and similar time schedules.The direct output of campaigned gravity survey is discrete time-variable gravity data.Each station in the network is visited with a fixed time interval（half or one years）,in order to measure the time-variable gravity change,which is at a scale few tens of microgals,at each station during the period between these two observations.Because the shape of gravity network is very irregular and the gravity changes is not significant compared with the observation error,the general gridding method is not suitable to visualize this sort of gravity data.In this paper,we proposed a new approach for the visualization of time-variable gravity data according to the data measured by the campaigned gravity survey.According to this approach,the patterns of gravity changes and uncertainty associated with the measurement can be visualized in the same figure with the gravity difference between two adjacent stations together.Furthermore,for the purpose of evaluating the magnitude of regional gravity change,we also defined two indexes,Gand C,to evaluate the significant levels of the regional gravity changes.On the basis of this approach,we analyzed the real campaigned gravity data in the capital area.The result show that the approaches are different from the classical contour map in expressing the regional gravity changes derived by the campaigned gravity survey,and can visualize and locate where the gravity changes happen,the reliable gravity changes and the level of significance.The approaches can provide more quantitative basis for the study of the gravity change potentially associated with the earthquake preparation and occurrence.