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2017年8月8日四川九寨沟MS7.0地震前甘肃南部地区视应力变化
陈丽娟1, 陈继锋2, 龚丽文1, 陈学忠3
1.重庆市地震局, 重庆市渝北区红黄路339号 401147;2.甘肃省地震局, 兰州 730000;3.中国地震局地球物理研究所, 北京 100081
摘要:
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ML≥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:①ML2.6~3.1、ML2.0~2.5震级段地震视应力的空间分布具有较好的一致性,九寨沟MS7.0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;②ML2.0~2.5、ML2.6~3.1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,ML2.6~3.1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ML2.0~2.5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,ML2.0~2.5、ML2.6~3.1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。
关键词:  九寨沟MS7.0地震  甘南地区  视应力
DOI:
分类号:P315
基金项目: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
The apparent stress variation in southern Gansu before the Jiuzhaigou MS7.0 earthquake in Sichuan on August 8,2017
Chen Lijuan1, Chen Jifeng2, Gong liwen1, Chen Xuezhong3
1.Earthquake Administration of Chongqing Municipality, Chongqing 401147, China;2.Earthquake Administration of Gansu Province, Lanzhou 730000, China;3.Institute of Geophysics, CEA, Beijing 100081, China
Abstract:
Based on the waveform data observed by the Regional Digital Seismic Network of Gansu Province, we calculated the apparent stress of the ML ≥ 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 ML2.0~2.5 and ML2.6~3.1 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 ML2.0~2.5 and ML2.6~3.1 was different within the large area:The apparent stress with ML2.6~3.1 was more apparent and increased significantly before the Jiuzhaigou earthquake, while the apparent stress with ML2.0~2.5 declined one or two year before. The spatial variation of apparent stress with ML2.0~2.5 and ML2.6~3.1 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.
Key words:  Jiuzhaigou MS7.0 earthquake  Southern Gansu area  Apparent stress