两次门源Ms6.4地震前垂直形变的对比分析

摘要

利用甘肃民乐至青海门源的多期跨断裂水准资料,对比分析了1986年、2016年两次门源6.4级地震前的垂直形变.结果表明:1)两次地震前的孕震背景不同.1986年门源地震前祁连山相对民乐盆地大幅上升,区域压应力呈增强状态;2016年门源地震前祁连山相对民乐盆地上升不明显,区域压应力相对松弛.2)两次地震前垂直形变表现形式不同.1986年门源地震前冷龙岭断裂附近出现加速上升,2016年门源地震前冷龙岭断裂附近出现上升和下降相间的不稳定变化.3)两次门源地震前在发震断裂附近都观测到地表隆起区,与地震孕育的膨胀模式相吻合.%Using multi period fault-crossing leveling data from Minle in Gansu province to Menyuan in Qinhai province,crust vertical deformation is analyzed comparatively before the 1986 and 2016 Menyuan MS 6.4 earthquakes.The results show that:1) The seismogenic background before the two earthquakes differs.Before the 1986 Menyuan earthquake,Qilian Mountains rise relatively sharply in Minle basin and the regional compressive stress state is enhanced;however,before 2016 earthquake,Qilian Mountains rise relatively insignificantly and the regional compressive stress is relaxed.2) The vertical deformation before the two Menyuan earthquakes also differs.Before the 1986 Menyuan earthquake,there is a rapid rise in the vicinity of the Lenglongling fauwhile before 2016 earthquake,there is an unstable change between the rise and fall in the vicinity of the Lenglongling fault.3) Surface uplift in the vicinity of seismic faults is observed before the two Menyuan Ms6.4 earthquakes,which is consistent with the expansion model of seismic development.