Dizhi lixue xuebao (Apr 2024)
The earthquake-controlling process of continental collision-extrusion active tectonic system around the Qinghai-Tibet Plateau: A case study of strong earthquakes since 1990
Abstract
Objective The Qinghai-Tibet Plateau is one of the most seismically active regions along the Mediterranean-Himalayan seismic belt. Understanding the earthquake-controlling effect of the active tectonic system in this region is crucial for analyzing regional strong earthquake hazards. Methods We analyzed earthquake activity with MW≥6.0 since 1990 and their tectonic mechanism around the Tibetan Plateau, focusing on the continental collision-extrusion tectonic system. Results The results show that the system plays a significant role in governing regional strong earthquake activity. Specifically, MW≥6.5 earthquakes primarily occur along the main boundary fault zone of this tectonic system, exhibiting a relatively regular spatio-temporal migration process. Moreover, the multi-layered extrusion-rotation active tectonic system in the eastern Tibetan Plateau constitutes the primary earthquake-controlling structure of the strong earthquake process since 1990, followed by the thrust faults of the Himalayan foreland. Therefore, the extrusion tectonic system of the Qinghai-Tibet Plateau should be the focus for the trend analysis of the strong earthquake activity in the future, especially the most active secondary extrusion tectonic units such as the Bayan Har block. Comparative analysis of strong earthquake activities in and around the Anatolian plate reveals similar continental collision-extrusion tectonic systems and earthquake-controlling effects in this area, indicating that this tectonic system is a typical earthquake-controlling structure in the intracontinental orogenic belt. Conclusion Further comprehensive analysis suggests that the active tectonic system can significantly control regional strong earthquake activity. Firstly, most of the strong earthquake events occur in the main boundary fault zone of the fault block in the tectonic system. Secondly, the strong earthquake events along different structural zones in the tectonic system often have linkage effects or mutual triggering relationships, and the complex or particular structural sites are often where double earthquakes or earthquake swarm activities easily occur. Thirdly, when a certain structural unit or tectonic zone in the tectonic system is in an active stage, strong earthquake clustering phenomena occur. Significance A thorough understanding of the coordinated deformation relationships between major active faults in the tectonic system, the segmented rupture behavior of strong earthquake activity in active fault zones, and the characteristics of "long period, quasi-periodicity and clustering" of strong earthquake recurrence in situ on active faults will assist in more accurately assessing the future seismic hazard of active fault zones when analyzing the future trend of strong earthquake activity based on the active tectonic system.
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