Liquefaction potential of Agartala City in Northeast India using a GIS platform

Abstract

Agartala is one of the fastest developing cities in Northeast Region (NER) of India and is also the capital city of Tripura state. The whole NER is in zone V in the seismic zoning map of India, one of the most seismic-prone regions in the world. The region is buttressed between the Himalayan collision zone to the north and Indo-Burma subduction zone to the east, and has experienced two (1897 and 1950) great earthquakes (Mw > 8.0) and several large earthquakes (Mw ≥ 7.0) since 1897. The Agartala area lies in an intraplate zone and most recently experienced a well-felt shallow (depth 30 km) earthquake of Mw 5.7 on January 3, 2017 that occurred at a distance ~75 km northeast of the city. Some evidence of liquefaction was identified along the Manu River in Kanchanbari village. In that context, this study is attempted to evaluate the liquefaction potential of the Agartala area. Dynamic properties of soil are determined using data of some 97 standard penetration test (SPT) boreholes. The cyclic shear stress of the soil layers is estimated considering a peak surface ground acceleration of 0.36 g. It is observed that according to the liquefaction potential index (LPI) scale, the central part of the city shows high to moderate, the northern part moderate to non-liquefiable and the southern part low to non-liquefiable potential. The results are presented in maps on a geographical information system (GIS) platform using the QGIS software. The liquefaction potential maps are very useful for professional engineers, government agencies and disaster management authorities for future development and planning of the city against liquefaction failure.