张家口地震台连续重力异常分析

张家口地震台gPhone连续重力观测仪潮汐因子自2016年6月出现持续下降的趋势变化,累计变化量达到7×10-3。分析重力残差曲线,异常出现时同期残差数据未出现同步变化;将去零漂前后潮汐因子的变化情况进行对比分析,发现潮汐因子变化趋势一致,排除仪器调零影响;针对新建楼房可能引起的重力变化,建立了重力正演模型,计算结果显示,新建楼房的荷载变化仅能引起0.31微伽的重力变化,表明新建楼房对重力观测的影响较弱。综合分析认为,此次出现的重力潮汐因子下降趋势异常可能为前兆异常,需加强跟踪分析。

Analysis of Continuous Gravity Anomaly at Zhangjiakou Seismic Station

Tidal factor of gPhone continuous gravity observatory at Zhangjiakou Seismic Station has been declining continuously since June 2016,with a cumulative decrease of 7×10-3.Analyzing the gravity residuals curve,the residuals data do not change synchronously when the anomaly occurs.Comparing and analyzing the change of the tidal factor before and after de-zero drift,it is found that the trend of the change of the tidal factor is the same,excluding the influence of zero adjustment of the instrument.A gravity forward model is established for the gravity variation that may be caused by a new building.The calculation results show that the load variation of the new building can only cause 0.31μGal gravity variation.The influence of the new building on gravity observation is relatively weak.Comprehensive analysis shows that the trend anomaly of decline of gravity tidal factor may be a precursor anomaly,so it is necessary to strengthen tracking and analysis.