Using LiDAR Data Visualization to Investigate Origin of Uphill-facing Scarps in Mountains, Alaska

Light Detection and Ranging (LIDAR) is a fast method for sampling the earth's surface with a high density and high accuracy point cloud that is used to generate high density and high accuracy Digital Elevation Models (DEMs) and DSMs. In this research we obtained airborne LIDAR elevation data with spatial resolution of I m to reveal new details of mountain block morphology and structure to investigate the origin of uphill facing scarps. Quaternary fault scarps occur in several mountain blocks in the western Saint Elias and Eastern Chugach Mountains of southern Alaska. Possible mechanisms for formation of these scarps include deformation caused by active folding, or deformation caused by gravitational loading and strong ground motion during earthquakes. The field observations and LIDAR visualization lead us to propose a three-stage model for flexural toppling. Failure is by flexural toppling, with rotation and shearing of bedding planes under the influence of gravity where bedding dips steeply into the mountain side. Down-slope bending of bedding surfaces may initiate formation of a basal sliding surface beneath the toppled beds, leading to landsliding down slope. However, horizontal acceleration caused by strong ground motion enhances the probability of failure by flexural toppling, especially in the upper parts of mountain slopes, where ground motion is amplified.