Landslide characteristics in the Loess Plateau, northern China

Abstract

Landslides play an important role in landscape evolution of the Loess Plateau, northern China, but they have not been systematically analysed across the region. The contribution to regional rates of erosion and sediment budgets is poorly known as a consequence. Co-seismic landslides are a significant natural hazard, and exacerbate the threat posed by active faults in the region, but this aspect of the landslides is also poorly quantified. This paper presents inventories for ~80,000 landslides in the Loess Plateau, and analyses the distributions and extents. Four study areas focus on the epicentres of major (M > 7) historical earthquakes, from 1303 CE (Hongdong), 1556 (Huaxian), 1718 (Tongwei) and 1920 (Haiyuan), which are likely to have been major triggers for landslides in these regions. A fifth study area focuses on landslides in the aftermath of localised storms in 2010 in the Tianshui region, to allow comparison of landslides clearly triggered by rainfall with landslides in the regional inventories. Landslides predominantly resulted from failure of the regional loess blanket that gives the region its name, or the soil profile developed above it. Rainfall-generated landslides are dominantly surficial soil landslides. Landslides preserved in the four epicentral areas are larger and deeper, and resemble global bedrock landslides in the dimensions. Total volume of landslide in each of the four epicentral areas are on the order of 3–7 km3; these volumes are likely to be the cumulative totals of repeated earthquakes in the same regions, with each event reactivating landslide scarps on hillsides. Comparison of landslide distributions and modern settlement patterns suggests that future M > 7 earthquakes striking the Loess Plateau may trigger landslides that could directly hit 30–50% of the communities.