Geomorphic and geologic controls of geohazards induced by Nepal’s 2015 Gorkha earthquake

Abstract

Nepal's quake-driven landslide hazards Large earthquakes can trigger dangerous landslides across a wide geographic region. The 2015 M w 7.8 Gorhka earthquake near Kathmandu, Nepal, was no exception. Kargal et al. used remote observations to compile a massive catalog of triggered debris flows. The satellite-based observations came from a rapid response team assisting the disaster relief effort. Schwanghart et al. show that Kathmandu escaped the historically catastrophic landslides associated with earthquakes in 1100, 1255, and 1344 C.E. near Nepal's second largest city, Pokhara. These two studies underscore the importance of determining slope stability in mountainous, earthquake-prone regions. Science , this issue p. 10.1126/science.aac8353 ; see also p. 147

Satellite-based emergency mapping using optical imagery: experience and reflections from the 2015 Nepal earthquakes

“…A clear exception to this finding is in assessing the imminent potential for secondary hazards posed by landslide dams (e.g., Cui et al, 2009;Kargel et al, 2016). It is widely recognized that landslide dams typically fail soon after formation, with 41 % failing within 1 week (Costa and Schuster, 1987).…”

“…For example, Xu (2015) described eight separate landslide inventories compiled after the 2008 Wenchuan earthquake in China. After the 2015 Nepal earthquakes, there was a 5-fold increase in landslide numbers between the inventories reported by Kargel et al (2016;4312), Martha et al (2016;15 551), Roback et al (2017;24 915), and Tiwari et al (2017;14 670). While some of these inventories were created in the immediate aftermath of the disaster, their use for scientific purposes nevertheless assumes complete coverage of the affected area.…”

“…Initial searches for landslide dams were therefore paramount, and dams that were identified were monitored until breached. This effort ran in parallel to several other initiatives that have subsequently been reported (Kargel et al, 2016;Roback et al, 2017;Tiwari et al, 2017).…”

“…It is also common to identify individual landslides rather than delineate areas impacted by multiple landslides (Guzzetti et al, 2012;. In global landslide databases (e.g., Kirschbaum et al, 2010;Petley, 2012) and many coseismic landslide inventories, landslides are specified as point features as an efficient means to locate and count large numbers of landslides (Kargel et al, 2016;Tiwari et al, 2017). Regional-to local-scale landslide inventory maps tend to document landslides as polygons, which can be used to understand impact zones or to separate source from deposit (Guzzetti, 2004;Guzzetti et al, 2012).…”

“…+ ∼ 5 days Enables locations with intense damage to be identified ability to appraise landslide size, mechanism, and risk. Kargel et al, 2016) (and hence, e.g., roads liable to blockage) and relative has suffered shaking sufficient to trigger landsliding (> × M W = 4.0; Keefer, 1984) should first be identified using initial outputs from USGS ShakeMap. Likely data availability arising from future satellite overpasses of this area should be assessed along with weather conditions to determine the extent of cloud cover.…”