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本文研究着眼于与民乐地区地震活动有紧密关联的地壳深度(≤20km),利用1987-2008年的Pg波到时数据反演了河西走廊及其周边地区的中、上地壳速度横向变化结果以及速度横向动态变化结果.分析表明:(1)河西走廊过渡带为低速区,北祁连褶皱带为高速区;(2)地震位于低速体南边与高速区相交的部位,且震前6年,震中边侧逐渐出现速度显著升高区;(3)研究区北东-南西的主压应力方向与两个速度升高区呈现出的延伸方向具有很好的一致性,这说明了在主压应力方向上更容易积累应力的合理性;(4)主震的静态应力变化与震后Pg波速度的横向动态变化有较好的对应关系.
This paper focuses on the crustal depth (≤20km) which is closely related to the seismic activity in Minle area. Using the Pg arrival-time data from 1987 to 2008, the lateral and upper crustal velocity variations in the Hexi Corridor and its surrounding areas are also analyzed. The results show that: (1) Hexi Corridor transition zone is low velocity zone and North Qilian fold zone is high velocity zone; (2) Earthquake is located in the intersection of high speed zone and south of low velocity body, and 6 years before the earthquake, (3) The direction of the principal compressive stress in the north-south west of the study area is in good agreement with the extension direction of the two velocity increasing regions, which shows that at the main pressure (4) There is a good correspondence between the static stress change of the main shock and the lateral dynamic change of Pg wave velocity after the earthquake.