THE APPLICATION OF REMOTE SENSING TECHNIQUES TO QUANTIFY LANDSLIDE MOVEMENT

Landslides can impact infrastructure after triggering events such as earthquakes and periods of significant precipitation, necessitating the quantification and monitoring of their ongoing movement. Landslides in 2023 and 2024 in Monterey and Humboldt counties had direct impacts on critical roadways and prompted local officials to request state assistance to analyze the potential for further movement to aid in roadway maintenance and realignment planning. The work presented here demonstrates that remotely-sensed data can be used to effectively and precisely quantify landslide movement that has occurred as a direct result of a triggering event and to monitor ongoing landslide movement. This is especially relevant to the engineering community with regard to safeguarding critical infrastructure after an earthquake. Multiple sensor platforms have been used to collect data to quantify landslide movement including spaceborne-based sensors (satellites) and airborne-based sensors (airplane and uncrewed aerial vehicles (UAV)). Data types used in methods to quantify regions of movement and displacement magnitudes include synthetic aperture radar (SAR), optical imagery, and lidar. Some examples of specific techniques applied to the collected data include optical image correlation, digital elevation model (DEM) differencing, and radar interferometry. Optical image correlation is a technique that enables the quantification of horizontal displacements both larger and smaller than the pixel resolution of image which means that high-resolution imagery can reliably resolve both large and small displacements. This analysis can be applied across platforms including airplane and UAV which allows for the monitoring of landslide movement via both airplane overflights and field visits with UAV flights, as often as is required. The mixing of platforms used (e.g. satellite, airplane, UAV) is most useful when baseline datasets do not match the platform being used to collect data immediately post-event or for monitoring purposes. The techniques and examples of analysis presented here illustrate the utility of remote sensing techniques to landslide response and could be relevant to landslide investigations and monitoring after a seismic event.