强震前典型重力场变化与数值预测实验

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。

Typical Gravity Changes before Strong Earthquakes and Numerical Prediction Test

We summarize the typical gravity changes (gradient zone and four quadrants distribution) and their quantitative parameters before seven strong earthquakes in the mainland of China. The results show that the earthquake prediction indicators used currently have a certain degree of uncertainty related to the observation time, the spatial distribution of stations and the spatial difference of variation amplitude. The spatial range of tidal factor anomalies before the Lushan earthquake is nearly 10 times the typical variation range of mobile gravity, which may be related to the fact that the measuring precision of continuous gravity stations are one order higher than mobile stations. Based on the locked shear force model, we propose a method for earthquake numerical prediction using the typical gravity changes. Before strong earthquakes, four-quadrants gravity changes on surface caused by strike-slip couple, or two-quadrants (gradient zone) gravity changes on surface aroused by dip-slip couple will appear under the continuous pushing of the locked double-couple shear force existing at the pregnant earthquake source. Preliminary results of the retrospective prediction cases show that the method is effective in predicting the magnitude of strike-slip and dip-slip earthquakes and can also give out the location and type of the future earthquakes.