Research on formation mechanism of the Huangcaoping landslide in the Batang fault, western Sichuan

There are a large number of landslides triggered by the earthquake in the Batang fault zone on the eastern margin of the Qinghai-Tibet Plateau, and some evidence of blocking the river are preserved. It is a good geological case for studying historical tectonic activities in the study area. This paper takes the Huangcaoping landslide in Batang County as a case, to study the development characteristics, formation, and evolution process of the landslide through remote sensing interpretation, ground investigation, geological dating, and engineering geological analysis. The study results are listed as follows: (1) The Huangcaoping landslide is a huge Holocene rock landslide in the Batang fault zone, developing in limestone and slate of the Middle-Lower Cambrian strata, with a volume of 142.5×10⁴~237.5×10⁴ m³. That the Baqu river has been blocked in history is proved by the evidence of the landslide dam and lacustrine sediments. (2) The Huangcaoping landslide was formed in about 7.75 ka B.P., the landslide dam failure was about in 1.07 ka B.P. from now, and the dammed lake had preserved more than 6.68 ka. (3) The Huangcaoping landslide is unlikely to be directly induced by rainfall, glaciers, and freeze-thaw. A strong earthquake caused by the violent activities of the Batang fault zone could be the direct triggering factor. Under the action of a strong earthquake, the slate near the fault at the toe of the slope is broken first. The upper limestone structural deteriorates and the sliding surface was formed. The sliding mass started as a whole and slid at a high speed to block the Baqu river. The study results can not only provide a reference for the analysis of the formation mechanism of similar landslides triggered by the earthquake in this region but also prove that the Batang fault zone is a Holocene active fault zone, which is of great significance for analyzing the activity of the Batang fault and improving the reconstruction of regional tectonic activity history.