Search

Knowledge of kinematics is crucial for understanding landslide mechanisms and assessing hazards. However, characterizing landslide kinematics is often challenging because landslides are sudden events with spatial and temporal coverage. Combining field investigations and remote sensing, the present study reveals the kinematic features, evolution processes, and triggering mechanism of a translational debris slide (the Tonghua landslide) that occurred on August 8 of 2017 in Sichuan Province, China. Based on digital orthophoto maps and digital elevation models derived from unmanned aerial vehicle photogrammetry, 3 years of post-failure kinematics were surveyed in detail. The landslide body experienced moderate-velocity (1.19–3.98 m/d) to slow-velocity (33.2–205.5 mm/d) sliding, eventually entering a period of very-slow-velocity (0.1–1.0 mm/d) sliding. A long-term pre-failure creeping process in the source area of the landslide was detected by interpreting interferometric synthetic aperture radar data and satellite images. At the front part of the source area, the observed deformation velocity was 15–25 mm/year between November 7, 2014 and July 30, 2017. Additionally, the source area of the landslide was found to be located on a hollow slope within a cirque catchment of ~ 67,500 m2. This complicated topographic feature promoted groundwater infiltration and long-term slope creeping; indeed, the 2008 Wenchuan earthquake may have aggravated surface cracking and soil weakening. Long-term creep of the slope caused cracking, saturation, and deformation of the soil body. Finally, seismic effects caused by tunnel blasting triggered sliding of the deformed soils. [ABSTRACT FROM AUTHOR]

The relationship between the North and South China blocks, particularly their spatial- temporal framework and evolutionary history, has been widely debated. We conducted a comprehensive study of the structural geometry and kinematics of the thrust belts in the intersection zone between the Dabashan and eastern Sichuan Basin based on seismic data, drilling data, field investigation data, and zircon and apatite (U-Th)/He thermochronology data. These data sets provide important insights into the relationship between the North and South China blocks during the post-orogenic process. Due to the detachments, the strata of the eastern Sichuan Basin can be divided into four structural intervals characterized by duplex structures and fault-related fold structures. Balanced restoration indicates the vertical differences are represented by the shortening ratio of the upper structural interval of ~6%, that of the middle ~10%, and that of the lower ~7%. Besides, the shortening ratios indicate an increasing tendency of the deformation intensity from the west to the east. The (U-Th)/ He dating results suggest two age ranges, i.e., from 180 Ma to 130 Ma and from 50 Ma to 20 Ma, respectively. These age data sets also imply a younger tendency westward. The intersection zone may have experienced the following stages since the late Mesozoic era: (1) the stable continental sedimentation stage from the Late Triassic to the Late Jurassic epochs; (2) the continuous thrust stage from the Late Jurassic to the early Paleogene epochs, which is associated with the subduction of the Paleo-Pacific Ocean; and (3) the uplift and denudation stage as a whole caused by the uplift of the Tibetan Plateau since the Paleogene period. [ABSTRACT FROM AUTHOR]

Abstract: According to the distribution and transfer directions of thrust displacements under which the size, shape and pattern of thrust belt are controlled, the foreland thrust belts are classified into four types in middle and western China: (1) Type I, all the fault displacements in the thrust belt transfer from the mountain front to the basin along detachment. This type is the most popular in central and western China and can be divided into three subtypes: Kuche type, southwestern Sichuan type and Jiuquan type. (2) Type II, represented by southern Junggar Basin, in which there are fault displacements transferring to both basin and orogenic belt directions. (3) Type III, represented by Fusha thrust belt in southwestern Tarim Basin, in which all the fault displacements transfer toward the mountain front as deep structural wedges propagating toward the basin direction. (4) Type IV, represented by southwestern and northern Qaidam Basin, in which the transfer of fault displacements is restrained by the size, shape and boundary of the basin, and the stable foreland part and typical wedge sedimentary structure not produced. On basis of the above four types and the modeling of complicated structures, four new exploration areas are identified: the deep imbricate structural wedges in southern Junggar Basin, late Paleozoic passive continental margin sequence under the reverse Cambrian nappe in northwestern Sichuan, under-coal structures in middle and eastern Kuche, and footwall covered structures in northwestern Junggar Basin. [Copyright &y& Elsevier]

The active kinematics of the eastern Tibetan Plateau are characterized by the southeastward movement of a major tectonic unit, the Chuan-Dian crustal fragment, bounded by the left-lateral Xianshuihe–Xiaojiang fault in the northeast and the right-lateral Red River–Ailao Shan shear zone in the southwest. Our field structural and geomorphic observations define two sets of young, active strike–slip faults within the northern part of the fragment that lie within the SE Tibetan Plateau. One set trends NE–SW with right-lateral displacement and includes the Jiulong, Batang, and Derong faults. The second set trends NW–SE with left-lateral displacement and includes the Xianshuihe, Litang, Xiangcheng, Zhongdian, and Xuebo faults. Strike–slip displacements along these faults were established by the deflection and offset of streams and various lithologic units; these offsets yield an average magnitude of right- and left-lateral displacements of ∼15–35 km. Using 5.7–3.5 Ma as the time of onset of the late-stage evolution of the Xianshuihe fault and the regional stream incision within this part of the plateau as a proxy for the initiation age of conjugate strike–slip faulting, we have determined an average slip rate of ∼2.6–9.4 mm/year. These two sets of strike–slip faults intersect at an obtuse angle that ranges from 100° to 140° facing east and west; the fault sets define a conjugate strike–slip pattern that expresses internal E–W shortening in the northern part of the Chuan-Dian crustal fragment. These conjugate faults are interpreted to have experienced clockwise and counterclockwise rotations of up to 20°. The presence of this conjugate fault system demonstrates that this part of the Tibetan Plateau is undergoing not only southward movement, but also E–W shortening and N–S lengthening due to convergence between the Sichuan Basin and the eastern Himalayan syntaxis. [ABSTRACT FROM AUTHOR]

On June 24, 2017, a catastrophic rock avalanche with a volume of 5.08 × 106 m occurred in Xinmo village, Maoxian County, Sichuan Province, SW China. Several studies focusing on the triggering factors, failure mechanism and dynamic process of the Xinmo landslide have been reported in the literature. However, there are few studies with detailed three-dimensional investigations based on numerical modeling that assess the post-failure stage of the landslide. In the present study, the three-dimensional material point method is used to reproduce the kinematics of the landslide to obtain better insight into the disaster by considering the effects of fragmentation and entrainment. Based on this framework, a velocity-weakening friction law is implemented to describe the basal friction between the moving mass and the substrate, and a strain–softening Drucker–Prager constitutive model is used to describe the internal deformation of the moving mass. The entrainment processes obtained with and without the proposed model are compared, and the simulated results generated with the presented models showing the distribution characteristics of the materials in the deposit area match the observed results fairly well. The implementation of a velocity-weakening friction law and a strain-softening Drucker–Prager constitutive model in the material point method may provide valuable insight for the enforcement of physically based risk assessments of "rockslide-debris avalanches". • The 3D material point method modeling of the Xinmo landslide overcomes some limitations of other numerical methods. • The model accurately reflected the effects of fragmentation and entrainment. • Kinematic energy curves were developed to examine the post-failure behavior of the Xinmo landslide. • Topography played a crucial role in kinetic energy growth and dissipation. [ABSTRACT FROM AUTHOR]