陕西重力网优化改造及监测能力评估

陕西重力网监测范围由关中盆地扩大到覆盖了鄂尔多斯块体南缘、关中盆地、秦岭山地及陕南、关中主要活动断裂带，同时与豫西、晋南、宁夏区域重力网实现了联网，测网监测能力由原来只具备对网内5级地震的监测提升到具备对发生在网内6级地震的监测。基于3个绝对重力基准约束下的重力观测平差结果表明，测网单位权中误差为7．7×10^-8 m·s-2，平均点值中误差7．9×10^-8m·s-2，当以2．5倍中误差作为限差时，可以识别发生在监测区域内40×10^-8m·s-2左右的重力相对变化，为研究鄂尔多斯块体南缘重力场变化提供依据。

Shaanxi Gravity Network optimization and monitoring capability assessment

Originally,Shaanxi Gravity Monitoring Network only covered Guanzhong basin.We ex-tended it to southern margin of Ordos′s block,Guanzhong basin,Qinling mountainous area and the main active faults of southern Shaanxi and Guanzhong.Meanwhile,we carried out the monitoring work by combing the local gravity monitoring network of western Henan, southern Shanxi,and Ningxia.Therefore,the monitoring ability was improved from monito-ring magnitude 5 earthquakes occurred within the network area to monitoring magnitude 6 earthquakes occurred within the network area.We processed the observation data based on a constraint of 3 absolute gravity data.The results indicate that the mean square error of unit weight is 7. 7 ×10^-8 m·s-2 ,and the average mean square error of observed points is 7. 9 × 10^-8 m·s-2 .It can detect the relative gravity change of 40 ×10^-8 m·s-2 within the network area,when the tolerance is set as 2. 5 times of mean square error.This monitoring ability provides a basis of studying gravity change in southern Ordos′s block.