甘肃岷县漳县6.6级地震前后区域地壳形变分析
Regional Crustal Deformation Analysis before and after the Minxian-Zhangxian Earthquake

利用陆态网GNSS连续站及流动站观测数据处理结果,从坐标时间序列、基线时间序列、速度场、形变场等方面分析岷县漳县地震前后青藏高原东北缘地区GPS形变场变化,得出以下结论:岷县漳县地震前GNSS测站时间序列没有明显变化,震前异常不突出;地震引起不同测点不同程度的永久性同震位移,最大值达到16 mm;地震前后基线变化不明显,未发现明显的前兆异常;阿拉善及附近的祁连构造带存在顺时针运动的迹象,即运动方向由东侧的南西向逐渐变到西部的北西向,运动大小的范围基本保持在7 mm/a之内;区域主压应变优势方向为东北-西南向,最大主压应变区呈带状分布于研究区域南部。
With the establishment of the Crustal Movement Observation Network of China (CMONOC) and the China Tectonic Environment Monitoring Network (CMTEMN),earthquake coseismic displacement can be obtained through global navigation satellite system (GNSS) data processing and analysis.The calculated results can provide basic research data for further study on seismic dynamics characteristics and determination of future earthquake trends.Using the GNSS data processing results from CMTEMN and CMONOC,together with the coordinate time series from the continuous observation stations,the baseline time series between two stations and the velocity and deformation fields were investigated in this study.In addition,the global positioning system deformation field of the northeastern margin of the Qinghai-Tibet plateau before and after the Minxian-Zhangxian Earthquake was analyzed.The results showed that the coordinate time series of the GNSS stations showed no noticeable change before the Minxian-Zhangxian Earthquake,and there were no prominent anomalies before the earthquake.The earthquake caused different levels of permanent co-seismic displacement of various stations,the maximum of which was as much as 16 mm This GSMX station,which is near the epicenter in the Lintan-Dangchang fault,exhibited a noticeable coseismic displacement.The GSWD station had no coseismic displacement.Similarly, the GSLX station,which was far from the epicenter,also experienced no displacement.The strain change of the three stations proved that the east-west strain was primarily linear,and there was no noticeable imminent anomaly before the earthquake removal of the coseismic step.The north-south strain exhibited a cycle and a half phenomenon,which was related to a corresponding year cycle in a single point,so this was not an obvious imminent anomaly prior to the earthquake.In addition to the obvious linear change,the north-east shear strain showed specific cycles,but no obvious anomalies before the quake,and these were restored to their original displacement after the quake.The GNSS baseline length change was based on the unity of the reference frame,so it was unaffected by the reference benchmark,therefore,it would objectively reflect the dynamic changes of the relative motion between two stations.Therefore,the