Liquefaction potential for the Kathmandu Valley, Nepal: a sensitivity study

Abstract

An assessment of liquefaction potential for the Kathmandu Valley considering seasonal variability of the groundwater table has been conducted. To gain deeper understanding seven historical liquefaction records located adjacent to borehole datapoints (published in SAFER/GEO-591) were used to compare two methods for the estimation of liquefaction potential. Standard Penetration Test (SPT) blowcount data from 75 boreholes inform the new liquefaction potential maps. Various scenarios were modelled, i.e., seasonal variation of the groundwater table and peak ground acceleration. Ordinary kriging, implemented in ArcGIS, was used to prepare maps at urban scale. Liquefaction potential calculations using the methodology from (Sonmez, Environ Geol 44:862–871, 2003) provided a good match to the historical liquefaction records in the region. Seasonal variation of the groundwater table is shown to have a significant effect on the spatial distribution of calculated liquefaction potential across the valley. The less than anticipated liquefaction manifestations due to the Gorkha earthquake are possibly due to the seasonal water table level.

Site-characterization using 1D/2D/3D Site Response Modelling vis-à-vis Surface-consistent Probabilistic Seismic Hazard, Microzonation and Damage Potential Studies in the Six-Tectonic Ensemble consisting of Kashmir Himalaya to Northeast India

“…The seismic loading causes a sudden increase in pore water pressure and the gaps between soil grains, leading the soil to loosen its cohesive strength and behave like a liquid. The Brahmaputra Valley of Northeast India, Indo-Gangetic Foredeep, Bengal Basin and Northwest India are particularly susceptible to liquefaction, as documented in the regions such as Jammu (Ansari et al 2022), Kashmir Valley (Sana and Nath 2016), Lucknow (Kumar et al 2013), Delhi (Rao and Satyam 2007), Kathmandu (Subedi and Acharya 2022;Pokhrel et al 2022), Bengal Basin including Bangladesh (Nath et al 2022), Guwahati (Raghukanth and Das 2010), Agartala (Das et al 2019) and Imphal (Pallav et al 2012). A comprehensive analysis of soil liquefaction has been conducted for the present Tectonic Ensemble, utilizing geotechnical data to simulate liquefaction susceptibility due to historical earthquakes and predict probabilistic scenarios for the Basin.…”