Researchers at NASA’s Jet Propulsion Laboratory in Southern California used data from an airborne radar to measure the movement of the slow-moving landslides on the Palos Verdes Peninsula in Los Angeles County. The analysis determined that, during a four-week period in the fall of 2024, land in the residential area slid toward the ocean by as much as 4 inches (10 centimeters) per week.
Portions of the peninsula, which juts into the Pacific Ocean just south of the city of Los Angeles, are part of an ancient complex of landslides and has been moving for at least the past six decades, affecting hundreds of buildings in local communities. The motion accelerated, and the active area expanded following record-breaking rainfall in Southern California in 2023 and heavy precipitation in early 2024.
To create this visualization, the Advanced Rapid Imaging and Analysis (ARIA) team used data from four flights of NASA’s Uninhabited Aerial Vehicle Synthetic Aperture Radar (UAVSAR) that took place between Sept. 18 and Oct. 17. The UAVSAR instrument was mounted to a Gulfstream III jet flown out of NASA’s Armstrong Flight Research Center in Edwards, California, and the four flights were planned to estimate the speed and direction of the landslides in three dimensions.
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In the image above, colors indicate how fast parts of the landslide complex were moving in late September and October, with the darkest reds indicating the highest speeds. The arrows represent the direction of horizontal motion. The white solid lines are the boundaries of the active landslide area as defined in 2007 by the California Geological Survey.
“In effect, we’re seeing that the footprint of land experiencing significant impacts has expanded, and the speed is more than enough to put human life and infrastructure at risk,” said Alexander Handwerger, the JPL landslide scientist who performed the analysis.
The insights from the UAVSAR flights were part of a package of analyses by the ARIA team that also used data from ESA’s (the European Space Agency’s) Copernicus Sentinel-1A/B satellites. The analyses were provided to California officials to support the state’s response to the landslides and made available to the public at NASA’s Disaster Mapping Portal.
Handwerger is also the principal investigator for NASA’s upcoming Landslide Climate Change Experiment, which will use airborne radar to study how extreme wet or dry precipitation patterns influence landslides. The investigation will include flights over coastal slopes spanning the California coastline.
More About ARIA, UAVSAR
The ARIA mission is a collaboration between JPL and Caltech, which manages JPL for NASA, to leverage radar and optical remote-sensing, GPS, and seismic observations for science as well as to aid in disaster response. The project investigates the processes and impacts of earthquakes, volcanoes, landslides, fires, subsurface fluid movement, and other natural hazards.
UAVSAR has flown thousands of radar missions around the world since 2007, studying phenomena such as glaciers and ice sheets, vegetation in ecosystems, and natural hazards like earthquakes, volcanoes, and landslides.