Slow‐Moving Landslides Triggered by the 2016 Mw 7.8 Kaikōura Earthquake, New Zealand: A New InSAR Phase‐Gradient Based Time‐Series Approach

Abstract

AbstractEarthquake‐triggered slow‐moving landslides are not well studied mainly due to a lack of high‐resolution in‐situ geodetic observations both in time and space. Satellite‐based interferometric synthetic aperture radar (InSAR) has shown potential in landslides applications, however, it is challenging to detect earthquake‐triggered slow‐moving landslides over large areas due to the effects of post‐seismic tectonic deformations, atmospheric delays, and other spatially propagated errors (e.g., unwrapped errors caused by decorrelation noises). Here, we present a novel InSAR phase‐gradient‐based time‐series approach to detect slow‐moving landslides that triggered by the 2016 Mw 7.8 Kaikōura earthquake. Twenty‐one earthquake‐triggered large (>0.1 km2) slow‐moving landslides are detected and studied. Our results reveal decaying characteristics of the temporal evolutions of these landslides, that averagely 3.9 years after the earthquake, their post‐seismic velocity will decay by 90% to reach approximately the pre‐seismic level. Our study opens new perspectives for understanding mass balance of earthquakes and helps reduce associated hazards.