关键词: 青藏高原东北缘, Q值, 应力降, 视应力, 衰减模型

Abstract: The geometric attenuation model, Q value, source parameters of 444 earthquakes and the instrumental responses of 118 stations are obtained near the northeast margin of Qinghai-Tibet Plateau using the joint inversion method based on the three-component S-wave data of small and medium-sized earthquakes occurred during 2010 to 2019. The results shows that the geometric attenuation model in the study area conforms to a form of 3-segment piecewise function, while the inelastic attenuation model meet Q(f) = 401.8 × f 0.2963 based on this geometric attenuation model. Among the site responses of 118 stations, 88 site responses show characteristics of rock site, 20 site responses show amplification effect, particularly in the high frequency, and 10 site responses show the overall value below 1, which may be affected by the spatial anisotropy of velocity structure and Q value. Through the correlation study of local magnitude, moment magnitude, stress drop and apparent stress, it is found that the moment magnitude has a linear correlation with the local magnitude as a whole, and the local magnitude has a positive correlation with the earthquake stress drop and apparent stress as under the same moment magnitude. There is a significant statistical correlation between stress drop and apparent stress and an obvious linear correlation in logarithmic coordinate system. Under the same moment magnitude, the ratio of the apparent stress to the stress drop of the earthquake with lower local magnitude is higher, it means the seismic rupture is more sufficient, and the radiation energy is relatively small. While the ratio of apparent stress to stress drop is relatively low for the higher local magnitude, means the energy loss during fault rupture is relatively small, and the radiation energy is relatively high.

Key words: the northeast margin of Qinghai-Tibet Plateau, Q value, stress drop, apparent stress, attenuation model