Landslides Triggered by the 2015 Gorkha, Nepal Earthquake

Abstract

ABSTRACT:The 25 April 2015 Gorkha Mw 7.8 earthquake in central Nepal caused a large number of casualties and serious property losses, and also induced numerous landslides. Based on visual interpretation of high-resolution optical satellite images pre-and post-earthquake and field reconnaissance, we delineated 47,200 coseismic landslides with a total distribution extent more than 35,000 km 2 , which occupy a total area about 110 km 2 . On the basis of a scale relationship between landslide area (A) and volume (V), V = 1.3147 × A 1.2085 , the total volume of the coseismic landslides is estimated to be about 9.64 × 10 8 m 3 . Calculation yields that the landslide number density, area density, and volume density are 1.32km -2 , 0.31%, and 0.027m, respectively. The spatial distribution of these landslides is consistent with that of the mainshock and aftershocks and the inferred causative fault, indicating the effect of the earthquake energy release on the pattern on coseismic landslides. This study provides a new, more detailed and objective inventory of the landslides triggered by the Gorkha earthquake, which would be significant for further study of genesis of coseismic landslides, hazard assessment and the long-term impact of the slope failure on the geological environment in the earthquake-scarred region.

Role of landslides on the volume balance of the Nepal 2015 earthquake sequence

“…The integration of Roback et al 17 landslides in our inventory in unmapped area, show smaller differences in total landslide volumes due to a limited number of unmapped landslides, suggesting that they are both almost complete. A further comparison with volumes reported in Roback et al 17 , ranging from 130 to 1270 Mm 3 , and Xu et al 40 , equal to 964 Mm 3 , confirms the strong controls of inventories and empirical relationships in the assessment of the landslide volume.…”

Geomorphometry and Statistical Analyses of Landslides Triggered by the 2015 Mw 7.8 Gorkha Earthquake and the Mw 7.3 Aftershock, Nepal

“…TH: Tethyan Himalaya, HH: High Himalaya; LH: Lesser Himalaya; SH: sub-Himalaya; STDS: South Tibetan Detachment System; MCT: Main Central Thrust; MBT: Main Boundary Thrust; PT2: Physiographic Transition [digitalized from Whipple et al (2016)]. Dataset 1 (22,914 landslides that are >500 m 2 and have L and W both >20 m) and Dataset 2 (2,059 landslides, which are >10,000 m 2 ) are from Xu et al (2018).…”

“…Combining with field investigations (Tian et al, 2020), Xu et al (2018) prepared an inventory containing ∼47,200 landslides in an area of 35,664 km 2 based on pre-and post-seismic remote sensing images from the Google Earth and the Chinese Gaofen and Ziyuan satellites. The DEM in our research has 10 mresolution pixels, and aids in identifying 22,914 landslides that are each >500 m 2 in area and have L and W >20 m; each landslide has at least one pixel in its narrowest profile.…”

“…Field surveys and synthetic aperture radar (SAR) analysis suggest that the earthquake-triggered landslides were the leading cause of the casualties, injuries, and financial damages in the affected area (Collins and Jibson, 2015;Moss et al, 2015;Yun et al, 2015). In all, the 2015 Gorkha earthquakes triggered >47,200 landslides (Xu et al, 2018). The Langtang landslide, in the Rasuwa region of Nepal, was the most colossal slope failure that was triggered by the Gorkha earthquake; it swept across the village of Langtang, resulting in >200 deaths (Collins and Jibson, 2015).…”

“…In this paper, we present an extensive study of the landslides to consider further the geomorphometric features of the landslides triggered by the 2015 Gorkha earthquake and to understand better the variety and nature of earthquake-triggered landslides in high mountain regions. Using the >47,200 landslides of Xu et al (2018), we study landslides with areas >500 m 2 and lengths and widths longer than 20 m (totally 22,914 landslides) to make an exhaustive analysis of their geometry, including the H, L, W, H/L ratio and aspect ratio. According to their aspect ratios, they are classified into three categories to statistically study their spatial distribution patterns with control factors, including terrain, geology, seismicity, streams, roads, and rainfalls.…”