Abstract: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.
TAN Hongbo,SHEN Chongyang,HUANG Haozhe et al. Typical Gravity Changes before Strong Earthquakes and Numerical Prediction Test[J]. jgg, 2021, 41(11): 1133-1140.