Seismic Liquefaction Risk Assessment of Critical Facilities in Kathmandu Valley, Nepal

Prabin Acharya,Keshab Sharma,Indra Prasad Acharya

doi:10.3390/geohazards2030009

Prabin Acharya, Keshab Sharma + Show 1 more

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https://doi.org/10.3390/geohazards2030009

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Abstract

Kathmandu Valley lies in an active tectonic zone, meaning that earthquakes are common in the region. The most recent was the Gorkha Nepal earthquake, measuring 7.8 Mw. Past earthquakes caused soil liquefaction in the valley with severe damages and destruction of existing critical infrastructures. As for such infrastructures, the road network, health facilities, schools and airports are considered. This paper presents a liquefaction susceptibility map. This map was obtained by computing the liquefaction potential index (LPI) for several boreholes with SPT measurements and clustering the areas with similar values of LPI. Moreover, the locations of existing critical infrastructures were reported on this risk map. Therefore, we noted that 42% of the road network and 16% of the airport area are in zones of very high liquefaction susceptibility, while 60%, 54%, and 64% of health facilities, schools and colleges are in very high liquefaction zones, respectively. This indicates that most of the critical facilities in the valley are at serious risk of liquefaction during a major earthquake and therefore should be retrofitted for their proper functioning during such disasters.

Highlights

Nepal lies in one of the most active tectonic zones of the world, making the region extremely vulnerable to earthquakes
The plot ofand schools and colleges in the liquefaction susceptibility map indicates that schools and colleges in very map highof liquefaction susceptibility wereof54%
The category very high andishigh susceptibility for liquefaction observed at the liquefaction are located along edges of the valley where a smaller numberat of central part ofzones the valley, while low tothe very low potential of liquefaction was observed schools and colleges can be seen

Summary

Introduction

Nepal lies in one of the most active tectonic zones of the world, making the region extremely vulnerable to earthquakes. The first liquefaction was reported during the 1934 Nepal–Bihar earthquake (Figure 1) in the form of ground fissures, cracks, subsidence, and sand boil up to the height of 4 to 5 m in Kathmandu. The most recent one, manifested in 2015 by the Gorkha, Nepal earthquake resulted in minor to major liquefaction in various locations of the valley (Figures 2 and 3). Liquefaction occurred in several parts of the valley, the surface manifestations of which were visible (Figure 2) at more than 20 sites in the form of sand boils, cracks on the ground surface, and bearing capacity failure in buildings [4–9]. The liquefaction suggested that the soil in the valley is highly prone to it, and the situation could have been worse if an earthquake with higher PGA had occurred in the rainy season (monsoon period). Several studies (e.g., [14–16]) reported a significant increment of the ground water table in the rainy season

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