Vegetation-landslide nexus and topographic changes post the 2004 Mw 6.6 Chuetsu earthquake

Abstract

Ground shaking on steep slopes often triggers numerous landslides, which dramatically modify the landscape and have long-term effects on vegetation dynamics. However, we still have a limited understanding of the quantitative topographic evolution and the duration of post-seismic impacts on the landscapes due to the lack of long-term consistent observation, especially in low-elevation mountain regions. To address this issue, we used high-resolution pre-and post-earthquake DEMs to investigate topographic changes, as well as multi-period and multi-scale remote sensing images to analyze the post-seismic landslides and vegetation recovery in the sites affected by the Mw 6.6 2004 Chuetsu earthquake, Japan. Using a vegetation recovery rate (VRR) time series from 2004 to 2021, we examined the decaying tendency of post-seismic landslide activities and predicted the vegetation recovery rate. Our findings indicate that the Chuetsu earthquake mostly steepens and roughens the terrain in low-elevation areas. The changes to slope aspects are associated with coseismic lateral displacement. The vegetation damage area accounted for 87.98 % of the entire area after the earthquake, and the VRR reaches 85.55 % by June 2021. The number of active landslides decreased to 14.45 % after 15 years. Meanwhile, we predict that vegetation recovery areas will be restored to pre-earthquake levels in 2024, and the landslide activity rate will decrease by less than 1 % in 2026, indicating a stable hillslope devoid of debris flows in the future.