Influence of Geological Structures in Aiding Landslide Initiation in Chimanimani, Zimbabwe

In March 2019, the Southeastern part of the Zimbabwe craton, Chimanimani, experienced a landslide that resulted in at least 350 deaths. There is considerable work currently ongoing in Chimanimani by researchers and experts to understand the landslides and prevent or minimise future damage. The objective of this study was to meticulously examine the role of geological structures in precipitating landslides using the Chimanimani district as a case study area. Comprehensive fieldwork encompassing site inspections, detailed structural mapping, petrographic analysis, and geotechnical assessments of outcrops was undertaken. The findings revealed that the region had experienced multiple deformation episodes, leading to its classification into three principal strain zones. These zones showed a positive correlation with historical and current landslide occurrences. It was noted that micro-faults were emerging progressively across various rock types. Both macroscopic and microscopic faults, along with joint systems, were identified as pivotal factors in both the onset and advancement of landslides. The majority of landslides were found on slopes with a concave upward geometry where fault planes inclined towards the slope's base. The orientation, continuity, and type of minerals filling the joints were also found to significantly influence landslide activity in Chimanimani. The presence of clay within micro-faults or joints was hypothesized to exacerbate fracture expansion due to its swelling properties upon moisture absorption. The study concluded that areas exhibiting a fault density exceeding 0.8km/km2 were highly susceptible to landslide events.