Earthquakes often cause large numbers of landslides which can magnify and prolong the damage associated with the shaking itself, with consequences that can extend for years after the shaking stops. Yet it remains difficult to predict landslides associated with earthquakes, especially those that occur over the years that follow. In 2015, a large earthquake in central Nepal caused tens of thousands of landslides, providing a natural experiment for understanding earthquake-triggered landsliding and its consequences. This project built on rapid response funding that supported mapping of landslides from satellite imagery and the collection of time-sensitive data from Nepal in the months following the earthquake. This award used these data, together with new fieldwork and data collection, to develop and apply new models for landslides associated with earthquakes, and particularly to evaluate how the physical and chemical properties of rocks evolve with time and control when and where landslides are likely to occur.

Research supported by this award included extensive field measurement of rock mass properties and shallow geophysical surveys across central Nepal. These data were used to interpret the mechanical strength of the near surface soil and rock profile, which is one of the main controls on landslide activity. We complemented the in-situ field measurements with an analysis of coseismic landslides that occurred during the Gorkha earthquake using remote sensing. Landslides represent locations in the landscape where the local shear strength of the rock or soil has been exceeded and thus offer an opportunity to estimate the shear strength of the rock mass at failure. Rainfall-triggered landslides during the intense summer monsoon period also contribute significantly to the erosional budget and long-term evolution of topography in the central Himalaya. As a part of this award, 10 years of monsoon triggered landslides before and after the Gorkha earthquake were inventoried from satellite imagery and paired with gauge and satellite derived precipitation data. Additional new data also included thermochronometry measurements on field samples, which were used to determine erosion rates across gradients in landslide activity. Together, the data from this award further supported the analysis of how landslides contribute to the evolution of topography in the Nepal Himalaya over thousands of years, driven by earthquakes and strong storms. The way that these events shape mountainous landscapes affects not only how we understand topography, but also how major erosional events feed back into generating the steep, landslide-prone slopes of mountain regions.

This award supported the research of 3 PhD students, one MS student, one postdoc, one undergraduate student, and one lab technician, contributing to their training in specific methods as well as general research skills including the synthesis and effective presentation of results. The project also enabled new collaboration with research partners in Nepal, including co-advisement of masters' students at Tribhuvan University. 

Last Modified: 04/17/2023
Modified by: Marin K Clark