利用甘肃省区域台网提供的地震波形资料，计算甘肃南部地区2010年1月～2017年8月M_L≥2.0地震的视应力，分析九寨沟地震前甘南地区视应力的时空演化特征，所得结果如下：①M_L2.6～3.1、M_L2.0～2.5震级段地震视应力的空间分布具有较好的一致性，九寨沟M_S7.0地震前，距震中较近的川甘交界地区的舟曲、文县等地呈现出较为集中的视应力高值异常；②M_L2.0～2.5、M_L2.6～3.1地震的视应力在大区域范围内随时间的变化趋势有一定差异，M_L2.6～3.1地震视应力变化更为明显，在较大区域范围内表现为震前显著升高，而M_L2.0～2.5地震视应力则在震前一两年内开始下降；③随着区域划分范围向震中靠近，M_L2.0～2.5、M_L2.6～3.1地震视应力的变化逐渐趋于一致，至震中附近时，2个震级段视应力均表现为“震前几年长时间升高—临震前几个月下降”的同步变化。

Based on the waveform data observed by the Regional Digital Seismic Network of Gansu Province, we calculated the apparent stress of the M_L ≥ 2.0 earthquakes in the southern Gansu from January 2010 to August 2017, and obtained the temporal-spatial variations of apparent stress. Results show that the distribution of apparent stress with M_L2.0~2.5 and M_L2.6~3.1 was consistent, both concentrating in the border region of Sichuan and Gansu before the Jiuzhaigou earthquake. The change trend of apparent stress over time with M_L2.0~2.5 and M_L2.6~3.1 was different within the large area:The apparent stress with M_L2.6~3.1 was more apparent and increased significantly before the Jiuzhaigou earthquake, while the apparent stress with M_L2.0~2.5 declined one or two year before. The spatial variation of apparent stress with M_L2.0~2.5 and M_L2.6~3.1 became more similar when the study area was closer to the epicenter, the apparent stress kept increasing a few years before the earthquake and suddenly declined a few months before the earthquake.

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重庆市地震局科研项目“用背景噪声和天然地震反演三峡库区岩石圈速度结构”资助