东昆仑断裂的震后粘弹性松弛效应对地壳变形的影响

Post-Seismic Viscoelastic Relaxation Effect of the East Kunlun Fault on Crustal Deformation

通过构建粘弹变形模型,对东昆仑断裂带附近近百年来发生的6个M≥7地震的震后粘弹性松弛效应进行数值模拟,分析该效应对区域地壳变形的影响。结果表明:1)离逝时间较短的1997年玛尼7.5级地震和2001年昆仑山口西8.1级地震造成的震后松弛效应对现今地壳变形的影响最为显著,在2次地震发生10~20 a后(2010~2020年)仍能造成最大约7.6 mm/a的地壳变形,跨断层变形速率最大约8.4 mm/a;2)2021年玛多7.4级地震震后粘弹效应在未来10 a内(2021~2030年)预计能造成最大约3.9 mm/a的地壳变形,2025~2030年跨断层变形速率可达2.6 mm/a。模拟结果表明,强震的震后粘弹性松弛效应对长期地壳变形和相关断层参数反演的影响不容忽视;3)考虑震后粘弹性松弛效应,采用跨断层GPS速度剖面反演的东昆仑断裂中段的滑移速率与地质学研究结果具有更好的一致性,若不考虑震后粘弹性松弛效应,则会明显高估30%的断层滑移率。

We construct viscoelastic deformation models and combine them with previous research results to investigate the post-seismic viscoelastic relaxation effect of six M≥7 earthquakes that occurred near the east Kunlun fault in the past century.We analyze the influence of this effect on regional crustal deformation.The results show that:1)The crustal deformation caused by post-seismic viscoelastic relaxation of the recent 1997 Manyi M7.5 and 2001 Kunlun M8.1 earthquakes is of great significance.It can cause a crustal deformation of up to 7.6 mm/a in 10-20 a(2010-2020)after the two earthquakes,leading a cross-fault deformation rate of 8.4 mm/a.2)The post-seismic viscoelastic relaxation of the 2021 Madoi M_(S)7.4 earthquake is estimated to cause a maximum crustal deformation of 3.9 mm/a in the next 10 a(2021-2030),and the cross-fault deformation rate can reach 2.6 mm/a in 2025-2030.These results suggest that the effect of post-seismic viscoelastic relaxation cannot be ignored when studying the long-term crustal deformation and associated inter-seismic fault slip rate.3)By considering the post-seismic viscoelastic deformation,the slip rate of the middle east Kunlun fault inferred from GPS velocity profile agrees well with the geological results;otherwise,the inferred slip rate will be clearly overestimated by 30%.