利用中国测震台网记录到的数字地震波形资料，通过波形分析和反演，获得了2017年8月8日四川九寨沟7.0级地震序列的视应力。研究表明：①在震后早期阶段九寨沟地震序列视应力水平较高，主震发生后不到1天视应力开始下降，主震发生1周后基本稳定，略有起伏；②震源区应力状态存在时空分段差异，余震区东南段视应力下降较快，而西北段下降较缓，最大余震发生前，东南段视应力水平略高或相当于西北段，最大余震发生至震后70天，西北段视应力水平高于东南段，这可能与余震区东南段比西北段破裂充分有关；③最大余震发生在主震震中东南侧视应力较高的区域，高视应力余震位于主震震中两侧靠近端部，与主震双侧扩展端部应力相对集中的结果一致。

In this paper, we apply the waveform analysis and inversion to determine the apparent stresses of the 2017 Jiuzhaigou M_S7.0 earthquake sequence by using the digital seismic waveform from the China Digital Seismograph Network. The main conclusions are:① The apparent stress of the Jiuzhaigou earthquake sequence was at relative high level in the early stage, and began to decrease in less than a day after the main shock. The apparent stress is at a stable level after the first week since the main shock, although the apparent stress curve had a slight fluctuation. ② The apparent stress showed temporal and spatial differences, the apparent stress level in the southeast section decreased more rapidly than the northwest section, and the mean apparent stress level in the southeast section was slightly higher than or equal to the northwest section in the early stage;while from the largest aftershock to 70 days after the main shock, the stress level in the northwest section was higher than the southeast section, which might be related to the more full rupture of the southeast section than the northwest section. ③ The largest aftershock occurred on the southeast side of the main shock, where the apparent stress was at a relative high level. The aftershocks of high apparent stress were nearly located at the both ends of the source areas, which was consistent with the relative concentration of the stress at these areas under the bilateral expansion of the main shock.

P315

地震科技星火计划（XH17034Y）、陕西省地震局启创与创新基金课题（QC201713）共同资助