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On August 14, 2020, it occurred a landslide-induced debris flow in Wangcang County, Sichuan Province, Southwest China, three people killed, and two houses destroyed. Behaved as a typical geohazard chain, it originated from a rockslide in marlstone, controlled initially by structural planes in rock mass, and evolved into a debris flow through successive geophysical process. This debris flow reached a run-out distance of 2050 m in the horizontal and 628 m in vertical direction. Remote sensing analysis, field survey, and laboratory tests were conducted to investigate its failure mechanism and dynamic characteristics. The results found that the source zone in the gully was 16.32 × 103 m2, with a volume of 317.52 × 103 m3. Interbedded marlstone with dense structural planes was one of controlling factors for the landslide failure. The continuous rainfall up to 315 mm during the previous 24 days and 32 mm at the date before the incident directly motivated rock slope failure. The contributions of topography, rock fragmentation, entrainment, and flow discharge for this process were discussed. It is found that changes in slope from 11° to 40° provided tremendous potential energy for the rock mass sliding with high speed and then disintegrating in traveling. Entrainment in the channel increased the fine content of the moving rocky mixture. In addition, the flow discharge changed the rheological properties of the mixture by adding seepage. These factors significantly affected the transformation process. Notably, the turning relief or confluence site may be accelerating this process. This research may provide references for further research on geohazard chains. [ABSTRACT FROM AUTHOR]

Landslide modeling based on seismic signal characteristics is an effective method to study landslide evolution. The scientific challenge lies in how to systematically characterize and reconstruct the entire landslide evolution process using the recorded seismic data. We selected the 2017 "6.24" Xinmo landslide as a case study. Empirical mode decomposition (EMD) is used to analyze the seismic signals from 14 seismic stations near the landslide area. Numerical simulations using two-dimensional discrete element methods (DEM) are performed to simulate landslide dynamics using the calculated kinetic energy profile. After analyzing the short-time Fourier transform (STFT) and fast Fourier transform (FFT) characteristics of the signal, the landslide process is reconstructed and compared with the DEM simulation. The landslide process is observed to consist of a stationary stage, slipping stage, transition stage, entrainment-transportation stage, and a deposition stage. This is the first study that uses seismic signals to identify a transition stage, which is a feature that is difficult to constrain from field survey and analysis alone. Landslide development and movement in the transition stage are discussed considering the sedimentology of the study area. This study provides improved theoretical guidance for the reconstruction and characterization of landslide processes by seismic signals. • Seismic signals generated by the Xinmo landslide (Sichuan - China) were analyzed. • 5 stages of landslide were recognized from spectral variations of seismic recording. • One transition stage was identified between first slipping and entrainment stage. • Discrete element simulations supported the landslide process reconstruction. [ABSTRACT FROM AUTHOR]