上海崇明长江农场深井综合地震观测系统地磁观测数据质量分析

Quality Analysis of Geomagnetic Observation Data Recorded by Comprehensive Seismic Observation System in Deep Borehole on Changjiang Farm in Shanghai

对上海崇明长江农场井深约460m的深井综合地震观测系统中的地磁观测数据进行质量分析。通过对该系统2套地磁仪以及相距约12km的三烈中学台地磁仪的时序图、相关性、频谱以及等效背景噪声水平对比分析,得出:(1)上海深井综合地震观测系统中用膨胀水泥固定在井深约460m岩石中的地磁仪工作正常,未受同一耐压腔体内应变仪、地温计、空隙压计传感器和安装在同一个钻孔内深度为430m左右的地震仪、倾斜仪传感器和系统影响,且相距60m远的长约400m的井下套管对其相对变化也未产生扰动;(2)长江农场深井地磁观测的等效背景噪声水平明显小于三烈中学台,开展深井地磁观测既能节约经费又能获得高于地表的观测数据质量,是值得推广的建设方式。

We mainly analyzed the quality of geomagnetic observation data recorded by comprehensive seismic obser- vation system which were installed at the depth of 460 m in deep borehole on Changjiang farm in Shanghai. Then we did a comparative analysis of sequence diagram, correlation, frequency spectrum and equivalent background noise of geomagnetic observation data recorded by magnetometers in Changjiang Farm Station （CJNC） and Sanlie Middle School Station （SLZX） which is 12 m apart from the CJNC Station. The result shows that： （1） The magnetometer was installed in well depth of 460 m by expanding cement works normally in the deep bore- hole comprehensive seismic observation system, and it doesn＇t interfered not only by the strain meter, geother- mometer, pore pressure meter which were installed in the same withstand voltage chamber, but also by the seis- mometer, tilt meter which were installed at depth of 430 m in the borehole, and it doesn＇t interfered by down- hole casing with 400 m long at a distance of 60 m. （2） The equivalent background noise of geomagnetic obser- vation data in deep borehole on Changjiang farm is obvious less than that in the surface observation of Sanlie Middle School. Geomagnetic observation in deep borehole not only can save outlay but also can obtain higher quality observation data than the surface observation, so it is worth popularizing.