LIQUEFACTION POTENTIAL ANALYSIS OF MIRPUR AREA

Abstract

Pakistan is one of the most seismically active regions in the world. Geologically, Pakistan lies on both Indian and Eurasian Tectonic plates. The region contains plate boundaries and major crustal faults which lead to severe earthquakes, causing loses to the communities. High density population centers are dangerously near seismic geo-hazards, Mirpur region is one of them. Liquefaction is one of the destructive phenomena caused by seismicity. Recently, liquefaction was observed in Mirpur region in earthquake on September 24th, 2019. So, we conducted SPT and seismic refraction tests in Southern Mirpur tehsil, Azad Jammu & Kashmir (target area) and some lab tests on the samples collected i.e. sieve analysis and Atterburg limits tests. From seismic refraction test, we obtained S-wave velocities. In our case, S-wave velocities are generally small, which means the likelihood of high liquefaction potential. Initially, we used two liquefaction screening criteria and then, by liquefaction potential evaluation by Iwasaki et. al. 1981 and Idriss and Boulanger 2008 (in Microsoft Excel, 2010), we obtained liquefaction potential indices and liquefaction probabilities (probabilities are calculated by nominal factor of safety by Juang, et al. 2013), which we used to generate a liquefaction hazard maps of the target area in ArcMap 10.6. The maps show high liquefaction potential of the whole area of Southern Mirpur Tehsil, AJK. We also made an android app, named GeoLiq, in which, there is a liquefaction screening criteria and two liquefaction potential evaluation methods. Values are to be inputted and the app will give outputs like factor of safety (FOS), liquefaction potential index (IL) or liquefaction probability (PL) and description on the basis of IL or PL values.