2016年青海门源MS6.4地震震前应变积累及同震变形特征

2016年1月21日青海省门源县发生了M_S6.4地震, 发震断裂为冷龙岭北侧断裂, 震中位置与1986年门源6.4级地震相同。 本文收集了本次地震震中及其周边区域1999—2015年GPS观测资料, 解算了GPS速度场、 跨断裂连续观测站基线时间序列和应变率场。 结果显示, 祁连山断裂带为一条宽度约60 km的连续变形带。 在断裂带南侧地壳运动以顺时针旋转为主, 运动量值没有显著差异; 跨过断裂带到达其北部之后, 地壳运动量值明显减小, 显示出该断裂带的强烈活动特征。 冷龙岭断裂左旋走滑速率为6.17±0.41 mm/a, 挤压速率为1.83±0.38 mm/a, 断层闭锁深度为22.1±3.1 km。 利用GPS连续观测站数据解算的地震同震位移显示, 震中西南侧26.8 km处的青海门源(QHME)测站记录到了明显同震位移, 其水平运动方向为北东向, 与逆冲为主的震源机制解一致。

Pre-seismic Strain Accumulation and Co-seismic Deformation from the 2016 Menyuan MS6.4 earthquake

Menyuan M_S6.4 earthquake occurred on 21 January 2016 in Menyuan County of Qinghai Province. We collected all GPS data during the period from 1999 to 2015 in the seismic source area and its vicinity, and estimated GPS velocity field by the weighted least square method and cross-fault GPS site baseline time series and GPS strain rate field by multi-scale spherical wavelet method. The results indicate that the Qilian fault zone was characterized by ~60 wide continuous belts. In the south side of the Qilian fault zone, GPS velocity field is featured by clockwise rotation, whereas, the vaule shows no significant change. Across the Qilian fault zone and to its north side, the size of GPS velocity is significantly reduced, which shows that the Qilian fault zone is an active tectonic belt. The sinistral strike-slip rate along the West segment of Lenglongling fault is 6.17±0.41 mm/a, with the compressive rate of 1.83±0.38 mm/a and the locking depth of 22.1±3.1 km. by calculating the coseismic displacements measured by fiducial GPS caused by the earthquake. We found that it is significant only at QHME site that is 26.8 km southwest of the epicenter. The northeast movement of the hozizontal coseismic displacement at QHME site is in agreement with the focal mechanism from the inversion of seismic data.