大同地震监测中心站GM4-XL磁通门磁力仪观测数据漂移分析

大同地震监测中心站配备2套GM4-XL磁通门磁力仪进行地磁观测，探头置于同一地下地磁房。自2017年以来，2套仪器每年夏秋季均存在不同程度的数据漂移现象。从数据连续率、完整率及台站背景噪声、数据预处理等角度，对2017年以来观测数据进行质量评价。通过与山西省其他台站地磁数据进行差值检测，结合地磁房附近地质条件、地下地磁室及观测墩建设、降雨等因素，分析认为，大同地震监测中心站地磁观测数据漂移的原因在于，夏秋季降雨致土层渗水，玻璃钢罩密封性较差，探头室地面积水，造成观测墩基不稳，使得置于观测墩上的仪器探头水平状态改变，进而引起观测数据发生漂移。

The analysis of the causes of GM4-XL observation data drift at Datong Seismic Station

The Datong Seismic Station is equipped with two sets of GM4-XL fluxgate magnetometers for geomagnetic observation. The probes are placed in the same underground geomagnetic room. The two sets of instruments have different degrees of data drift in each summer and autumn since 2017. This study evaluates the quality of the observation data since 2017 from the perspectives of continuity rate, integrity rate, background noise and data preprocessing. Through the difference detection with the geomagnetic data of other stations in Shanxi Province, the analysis is carried out in combination with the geological conditions near the geomagnetic room, the construction of the underground geomagnetic room and the observation pier, and the rainfall. It is believed that the reason for the drift of GM4-XL data at Datong Seismic Station is that the stratum soil is easy to seep after rainfall in summer and autumn. The underground glass steel cover is not well sealed, which leads to water in the probe room. The instability of the observation pier foundation causes the level of the instrument probe placed on it to change, which in turn causes the observation data to drift.