The b-value spatiotemporal evolution in southeastern Tibetan Plateau and its implications on regional stress field characteristics

doi:10.7523/j.ucas.2021.0037

Abstract

Abstract: Stress field is an important factor to assess regional seismic risk. We collected the seismic catalogue data from 1970 to 2019 in southeastern Tibetan Plateau, used the maximum likelihood method to calculate regional b values, and then obtained the spatial and temporal distribution of b values of this region. Based on the negative correlation between seismic b value and stress, we analyzed the stress distribution and variation on the major fault zones in southeastern Tibetan Plateau. The results are as follows. 1) In the center of Xianshuihe-Xiaojiang fault system, the b value of Daliangshan fault zone is lower than that of Anninghe-Zemuhe fault zone. This indicates that the stress on Daliangshan fault zone is greater and its seismic risk is relatively high in the future. 2) The b values in shallow layer (0-20 km) are higher than those of deep layer (20-40 km), which is consistent with the characteristics that confining pressure is low and rock tends to brittle fracture in the shallow, while confining pressure is high and rock tends to ductile deformation in the deep. 3) Before and after the 2008 Wenchuan earthquake, b value of epicenter area had a decrease-rise-decrease process, and this showed the accumulation-release-accumulation process of regional stress. The larger the magnitude of earthquake, the longer the decreasing trend of b value before the earthquake, the greater the impact of earthquake on b value. The closer to the epicenter, the greater the decrease of b value. 4) The b value of Longmenshan fault zone is relatively low at present and this shows that Longmenshan fault zone is accumulating stress.

Key words: b value, magnitude-frequency, southeastern Tibetan Plateau, stress field, Longmenshan fault zone

CLC Number:

P315.5

GAO Yajing, LUO Gang, WANG Shaopo, ZHOU Yuanze. The b-value spatiotemporal evolution in southeastern Tibetan Plateau and its implications on regional stress field characteristics[J]. Journal of University of Chinese Academy of Sciences, 2022, 39(5): 627-638.

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