Located at the western edge of the Tu Le Basin in Northwest Vietnam, the Pieng stream catchment in Nam Pam commune, Muong La District, Son La Province, has been highly prone to landslides both historically and recently. However, the causes of the complex geomorphic characteristics and landslide occurrences in this area are unclear. This study aims to investigate the connection between landslides and faults through in-depth analyses of DEM-derived geomorphology, field observations, geophysical profiles, and soil mineralogy. On the basis of evidence of triangular facet patterns, observations of fault slickensides and knickpoints along stream longitudinal profiles identified by a relative slope-extension (RDEs) index and a total RDE (RDEt) index, there are two main fault systems: NE–SW and NW–SE-trending fault systems. These faults were further examined via electrical resistivity tomography and seismic refraction tomography. The results of the soil analysis along the three boreholes indicate that the weathering material consists of two main layers, with weathering profiles ranging from silty to sandy materials. The dominant minerals are kaolinite, mica, feldspar and quartz, whereas the main components are SiO 2 , Al 2 O 3 and Fe 2 O 3 . Soil mechanical and physical tests indicate that the local soil has weak physical and mechanical properties. A total of 140 landslides were interpreted using Planet Scope images, a DEM, and field surveys. The relationships between landslides and faults are reflected in three aspects: triangular facets, distance to faults and fault density, and the presence of weak minerals along fault zones.
Tran et al. (Thu,) studied this question.