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.
Highlights
The Kathmandu Valley is located approximately 10 km from the Main Himalayan Thrust (MHT) (Elliott et al 2016)
At each borehole location in the SAFER/GEO-591 database used for the liquefaction potential analysis, two different seasonal values of water table depth were used
Information compiled from geo-database SAFER/GEO-591 was employed to develop new maps of liquefaction potential using Standard Penetration Test (SPT) data
Summary
The Kathmandu Valley is located approximately 10 km from the Main Himalayan Thrust (MHT) (Elliott et al 2016) This geographical area experienced several destructive earthquakes in the past: the latest significant event occurred in 2015, the Mw 7.8 Gorkha earthquake (Grandin et al 2015). The study of Moss et al (2017) demonstrated that evidence of liquefaction in the aftermath of the 2015 Gorkha earthquake was less significant than expected. Possible reasons for this may include: changes in the groundwater table due to extraction (e.g., Pandey et al 2012); seasonal variation of groundwater table level
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