2017年九寨沟7.0级地震前应力状态及b值异常特征研究

Stress State and b-value Anomalies before the Jiuzhaigou MS7.0 Earthquake in 2017

摘要:

2017年8月8日青藏高原东缘四川九寨沟地区发生7.0级强震，依据前人研究结果分析九寨沟7.0级地震发震构造，并计算震前应力状态。结果显示：本次地震受到构造和历史强震的影响，是发生在历史强震引起的应力加载区域。另外，采用中国地震台网1990年以来的地震目录，在评估目录完整性的基础上，利用最大似然法计算得到2017年8月8日九寨沟7.0级地震前震源区及邻区地震b值空间图像。结果显示，九寨沟7.0级地震发生在四川北部地区显著低b值高应力异常区域内部（0.82>b>0.75）。所以，研究区域内外历史强震可能促进了九寨沟7.0级地震的发生。

Abstract:

On August 8, 2017, an M_S7.0 earthquake occurred in Jiuzhaigou area, Sichuan Province. Based on the results of previous research, the seismogenic structure of the earthquake was analyzed and the stress state before the earthquake was calculated. The results showed that the M_S7.0 earthquake was affected by tectonic activity and historical strong earthquakes, and occurred in the stress loading area caused by historical strong earthquakes. In addition, based on the integrity evaluation of the earthquake catalogue of China Earthquake Network since 1990, the spatial images of seismic b-value in the epicenter area and adjacent areas before the Jiuzhaigou M_S7.0 earthquake were calculated by adopting the maximum likelihood method. The calculation results showed that the M_S7.0 earthquake occurred in the region with significant low b-value and high stress anomalies of northern Sichuan (0.82>b>0.75). Therefore, the historical strong earthquakes in the study area may promote the occurrence of the Jiuzhaigou M_S7.0 earthquake.