2021年甘肃阿克塞5.5级地震前区域地壳变形异常特征分析

为研究2021年甘肃阿克塞5.5级地震前震中周边的地壳变形运动特征，根据CMONOC提供的GPS观测资料，通过GPS速度场、面应变率场和站间基线时间序列分析，探讨了震前的地壳变形特征。研究结果表明，震中处于发震断层西南侧远场速度大、近场速度小且断裂两侧速度场方向明显不同的位置，同时位于与发震构造类型一致的面应变率场的压缩高值区，即挤压应变累积区。跨发震断裂的基线长度在震前3年多时间出现的转折变化，表明震前发震断裂两侧左旋走滑速率明显减缓；而断裂两侧的挤压速率有所加快则反映出本次地震前震中区域存在一定程度的应变能积累。研究结果有助于认识该地震的孕震过程，并可为相似构造类型区域的强震预测提供参考依据。

Anomaly characteristics of regional crustal deformationbefore the Aksai M5.5 earthquake

The characteristics of crustal deformation movement around the epicenter before the Aksai M5.5 earthquake in 2021 were studied in this paper. According to the GPS observation data provided by CMONOC, the characteristics of crustal deformation before the M5.5 earthquake were discussed by the GPS velocity field analysis, the area strain rate field analysis, and the baseline time series between stations. The results show that the epicenter of Aksai M5.5 earthquake is located in the southwest side of the seismogenic fault, where the far-field velocity is large and the near-field velocity is small, and the velocity field directions are obviously different on both sides of the seismogenic fault. It is also located in the high-value area of the compressive area strain rate field consistent with the type of seismogenic structure, namely the compressive strain accumulation area. The turning change of baseline length across the seismogenic fault more than 3 years before the earthquake indicates that the left-lateral strike-slip rate on both sides of the seismogenic fault decreased significantly before the earthquake. The acceleration of the compression rate on both sides of the fault reflects that the strain energy accumulated before the earthquake. The results can provide basic research data for understanding the seismogenic process of the Aksai M5.5 earthquake. Besides, it can provide a reference for the prediction of strong earthquakes in areas with similar structural types.