The Impact of the 1668 Tancheng M 8½ Earthquake on the Banquan Pull-Apart Basin
Key Highlights :
The 1668 Tancheng M 8½ earthquake was one of the most devastating earthquakes in Chinese history. It caused massive destruction in the region and left a lasting legacy on the landscape. The Tanlu Fault Zone (TLFZ) is one of the major fault systems that was affected by the earthquake and its seismic activity has been the strongest in the region ever since. The Banquan Basin is the largest and most typical pull-apart basin along the surface rupture zone of the 1668 Tancheng M 8½ earthquake. In a recent study, researchers (Peng Shu, Xiwei Xu, Shaoying Feng, et al.,) studied the sedimentary and tectonic evolution of the Banquan Basin and discussed the start time and tectonic significance of the right-lateral strike-slip of the TLFZ.
The study showed that the Banquan basin has undergone three main evolutionary stages. During the pre-pull-apart period, the TLFZ that controls the evolution of the basin showed very weak activity, and then fault activity intensified and led to two periods of pull-apart and extension of the basin. During these two periods, especially in the second period of pull-apart and extension, fault activity migrated to the central basin. Then, the basin expansion reached its peak. Following that period, the basin entered the subsidence stage. New strike-slip fault formed in the center of the basin, which effectively accommodated normal faulting of the boundary faults of the basin and caused the basin to shrink and die out.
The sedimentary filling and depositional cycle of the basin has strong response to the episodic pull-apart and extension of the basin. Before the intense pull-apart, a thin layer of Miocene mudstone slowly accumulated in the basin due to local rifting. In the early and late stages of pull-apart and extension, the basin was successively filled with coarse-grained alluvial fan facies (sedimentary system I) and braided river-meandering river facies (sedimentary system II) with frequent facies changes. During the subsidence stage of post-pull-apart, the basin was filled with a set of floodplain facies deposits (sedimentary system III).
The sedimentary and tectonic evolution of the Banquan Basin was directly controlled by strike-slip movement of the TLFZ. The latest tectonic movement of the TLFZ in late Cenozoic was dominated by episodic dextral strike-slip movement that started at 4.01±1.27 Ma. By comprehensive analysis of dynamic background of eastern China, the authors held that the latest tectonic deformation of the North China Plain has been governed by the eastward tectonic extrusion and orogenesis of the eastern margin of the Tibetan Plateau since late Miocene. The eastward thrusting of the Liupanshan fault zone and sinistral shearing of the Qinling fault zone led to anticlockwise rotation and pushing of secondary blocks in North China, resulting in a planar bookshelf faulting and rotation pattern.
This study provides an important insight into the sedimentary and tectonic evolution of the Banquan Basin as a result of the 1668 Tancheng M 8½ earthquake. It shows that the pull-apart basin faithfully records the strike-slip process of the faults that control the development of the pull-apart basins. The study also reveals the start time and tectonic significance of the right-lateral strike-slip of the TLFZ, which was likely to be the long-range effect of the strong extrusion of the eastern margin of the Tibetan Plateau. This research provides a better understanding of the impact of the 1668 Tancheng M 8½ earthquake on the Banquan Basin and helps to better understand the regional tectonic evolution of the North China Plain.
