Liquefaction hazard mapping by liquefaction potential index for Dhaka City, Bangladesh

Abstract

Preparation of liquefaction hazard map of prone areas has high importance for decision makers or site planners to reduce loss of lives. In this study, liquefaction hazard map of Dhaka City was prepared using liquefaction potential index (LPI) and cumulative frequency distribution of LPI of surface geological units, which is an excellent approach to evaluate the liquefaction hazard quantitatively and spatially. LPI values were calculated using Simplified Procedure of liquefaction potential assessment for 53 Standard Penetration Test (SPT) profiles conducted in different surface geological units of the city. The LPI values of the city varied from 0 to 19.33 having very low to very high liquefaction hazard. The hazard of each unit was also defined by cumulative frequency at LPI=5 which may be evaluated as the threshold for observation effects of liquefaction on surface. The geological units of the city were grouped into three liquefaction hazard zones, i.e., Zone 1, Zone 2 and Zone 3 based on cumulative frequency. The hazard map indicates that 8%, 50% and 72% of Zone 1, Zone 2 and Zone 3, respectively, will show surface manifestation of liquefaction for an earthquake scenario having a magnitude of 7.0 (Mw) and a peak ground acceleration of 0.15g.