青藏高原1990年以来的M_W≥6.5强震事件及活动构造体系控震效应

The MW≥6.5 strong earthquake events since 1990 around the Tibetan Plateau and control-earthquake effect of active tectonic system

深入认识青藏高原陆陆碰撞-挤出构造体系作用下的强震活动特点及未来强震活动趋势,对于区域防震减灾具有重要科学意义。统计分析青藏高原及邻区1900年以来的M≥6.0强震活动发现,青藏高原自1950年西藏墨脱—察隅8.6级大地震以来正处于新一轮相对缓慢的地震能释放期,但1990年以来的强震发生率和地震释放能显示出逐步增高趋势,并可能预示下一轮地震能快速释放期的临近。活动构造体系控震分析表明,青藏高原陆陆碰撞-挤出构造体系中的“多层次挤出-旋转活动构造体系”构成了1990年以来新一轮M_W≥6.5强震活动的主要控震构造,尤其是其中的巴颜喀拉挤出构造单元的强震活动最为显著,指示其目前正处于构造活跃状态,而且这一状态可能仍将持续。综合研究认为,在区域强震活动趋势分析中,充分认识活动构造体系控震效应,将有助于更好地分析判断区域未来强震时空迁移过程及最可能出现的构造部位。考虑到当前强震活动过程中,青藏高原“多层次挤出-旋转活动构造体系”的未来强震活动趋势仍会持续,需要重点关注挤出块体边界上3条大型左旋走滑断裂带,阿尔金—祁连—海原断裂系、东昆仑断裂带和鲜水河—小江断裂带的未来强震危险性,其次是断块内部断裂。

It is of great scientific significance for regional seismic prevention and disaster mitigation to understand the characteristics and future trends of strong earthquakes related with the active continental collision-extrusion tectonic system in the Tibetan Plateau.The characteristics of MW≥6.5 strong earthquakes since 1990 and the earthquake-controlling phenomena of the continental collision-extrusion tectonic system in the Tibetan Plateau are comprehensively analyzed.The results indicate that the Tibetan Plateau has been in the period of slow release of seismic energy recently,but may be approaching the next period of rapid release.The“multi-level extrusion-rotation active tectonic system”in the continental collision-extrusion tectonic system of the Tibetan Plateau plays a major role in controlling this strong earthquakes process.In particular,the Bayan Hara extrusion tectonic unit shows the most significant strong seismic activity process in this tectonic system.The results of comprehensive study suggest that the earthquake-controlling effect of active tectonic system should be fully recognized in the analysis of activity trend and hazard of regional strong earthquake,which is helpful to scientifically judge the space-time migration process and the most likely location of strong earthquakes in the future.In the process of the current strong earthquake activity,the strong earthquake activity trend of the“multi-level extrusion-rotation active tectonic deformation system”in the Tibetan Plateau will continue in future.In particular,more attention should be paid to the future strong earthquake hazard of three large left-lateral strike-slip fault zones which constitute the boundary of extrusion blocks in the“multi-level extrusion-rotation active tectonic deformation system”,including Altyn-Qilian-Haiyuan fault system,East Kunlun fault zone and Xianshuihe-Xiaojiang fault zone.