Two comparable earthquakes produced greatly different coseismic landslides: The 2015 Gorkha, Nepal and 2008 Wenchuan, China events

Abstract

The 2015 Gorkha Earthquake in Nepal and the 2008 Wenchuan Earthquake in China occurred at the south and southeast margins of the Tibetan Plateau, respectively. Both earthquakes had similar magnitudes of Mw 7.8 and 7.9, caused catastrophic loss of life and damage to property, and generated tens of thousands of landslides. Comparisons of pre-and post-quake satellite images supported by field investigations show that the Gorkha Earthquake triggered at least 2 064 large landslides (defined as covering an area ≥10 000 m 2 ) over a ~35 600 km 2 region with a volume of (444-584)×10 6 (average 509×10 6 ) m 3 and total area of 44.78×10 6 m 2 . In contrast, the Wenchuan Earthquake triggered 25 580 large landslides over a region of ~44 000 km 2 with a volume of (7 128-9 479)×10 6 (average 8 219×10 6 ) m 3 and a total area of about 670.65×10 6 m 2 . Several controlling factors including topographic relief, slope steepness, and regional peak ground acceleration (PGA) were investigated to try to explain the great differences between the number, volume and area of the coseismic landslides associated with the two similar earthquakes. We found that the differences primarily arose from an unexpected factor, the dip angle of the seismogenic fault. This discovery should aid understanding the failure mechanisms of quake-triggered landslides, and suggests that more factors should be taken into consideration in estimating coseismic landslide volumes from earthquake magnitudes.

Landslides Triggered by the 2015 Gorkha, Nepal Earthquake

“…The Landsat8 image of 15m resolution was supplemented to this 1% of the landslide distribution area. In addition, detailed field investigations were carried on along the Pasang Lhamu Highway that connects Kathmandu, Nepal and Gyirong County and the Araniko Highway that links Kathmandu, Nepal and Nielamu County, China for tens of days by cars or by walk (Xu et al 2016a). Figure 4 shows two groups of comparison of satellite images from the Google Earth platform and field photos of coseismic landslides to illustrate the high-resolution, good-quality, and excellent capacity of detecting coseismic landslides on highresolution satellite images, which permit to map the locations and boundaries of coseismic landslides correctly and conveniently (Xu et al 2017).…”

Does a Damaged‐Fault Zone Mitigate the Near‐Field Impact of Supershear Earthquakes?—Application to the 2018 7.5 Palu, Indonesia, Earthquake

“…Yet recent research points to the necessity of considering the combined effect of geo‐environmental factors and rupture complexities to improve the hazard prediction. For example, landslides triggered by the 2008 Wenchuan, China, earthquake were found to be unexpectedly high for a 7.9 event (Xu et al, ). Conversely, the 1999 7.2 Düzce, Turkey, and the 2002 7.9 Denali, USA, earthquakes induced fewer landslides than expected for 7+ earthquakes (Görüm et al, ).…”

“…Conversely, the 1999 7.2 Düzce, Turkey, and the 2002 7.9 Denali, USA, earthquakes induced fewer landslides than expected for 7+ earthquakes (Görüm et al, ). Indeed, despite the similarities of magnitude, topology, climate, and rock type, the difference between the 2015 7.8 Gorkha, Nepal, and the 2008 Wenchuan earthquake‐triggered landslide densities is mainly associated with the rupture complexities (Roback et al, ; Xu et al, ). For that reason, we also investigate the effect of rupture properties of the Palu earthquake on ground motion and consequent landslide triggering in the near field.…”

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

“…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). Studies on these landslides include field investigations, interpretations of imagery, spatial distribution, and susceptibility assessment (Collins and Jibson, 2015;Kargel et al, 2016;Martha et al, 2016;Regmi et al, 2016;Xu et al, 2016b;Xu et al, 2017;Roback et al, 2018;Tsou et al, 2018), but there was little geomorphometry research. Tsou et al (2018), e.g., presented a preliminary analysis on the planar geometry of the 912 seismic landslides in the Trishuli Valley, central Nepal following the Gorkha earthquake.…”