Contents lists available at ScienceDirect Soil Dynamics and Earthquake Engineering journal homepage: www.elsevier.com/locate/soildyn Seismic hazard assessment at micro level in Gandhinagar (the capital of Gujarat, India) considering soil effects Kapil Mohan ⁎ , B.K. Rastogi, Vasu Pancholi, Drasti Gandhi Institute of Seismological Research, Raisan, 382009 Gandhinagar, Gujarat, India ARTICLE INFO Keywords: Seismic hazard Micro level Soil modeling Peak ground acceleration Peak spectral acceleration ABSTRACT Gandhinagar City (the Capital of Gujarat, India) falls under Zone III on the seismic zoning map of India where an earthquake of magnitude 6 can be expected. It is a well established fact that the site amplification/ shaking and damage is large in soil covered areas. To estimate the effect of soil on ground motion and to estimate the strong ground motion parameters at surface, soil modeling and the ground response analysis have been conducted along uniformly distributed 14 boreholes drilled upto a depth of 50 m. The methodology is divided into three parts (i) Estimation of depth of Engineering Bed layer (EBL) (a layer with a shear wave velocity 400 m/ s ≤ Vs ≤ 750 m/s, N value > 80 and minimum soil variation below it) through soil modeling, (ii) Estimation of Ground Motion at EBL due to scenario earthquake at nearby active fault and (iii) Estimation of surface strong ground motion using 1D ground response analysis through SHAKE 2000 program. The EBL is found at a depth of 21–33 m (shallower in central part and deeper in northern and southern parts). The Near-Field scenario earthquake (Eq.) of magnitude Mw 6.0 has been considered along East Cambay Fault (normal fault, 60° dip) located at about ~ 20 km east and Far Field scenario Eq. of Mw 7.6 is considered along Kachchh Mainland Fault located ~270 km west. The Peak Ground acceleration (PGA) of 0.172–0.237 g have been estimated at surface due to near field earthquake scenario. The mean spectral acceleration maps for 0.1–0.4 s, 0.4–0.7 s, 0.7–1.0 s and 1.0–1.5 s have also been computed. The mean spectral acceleration for the period of 0.1–0.4 s has been varying from 0.330 g to 0.508 g, for period of 0.4–0.7 Sec, it has been varying from 0.151 g to 0.161 g and for period between 1.0 and 1.5 Sec, it has been found from 0.83 g to 0.09 g. The PGA is found increased by 5–38% in the first subsurface soil layer in Gandhinagar city. The PGA of the order of 0.059–0.072 g and peak Spectral ac- celeration of the order of 0.187–0.259 g have been computed (with predominant periods of ~0.1 s and 0.31 s) due to Far-Field Eq. scenario and are found less than Indian code. The PGA and Spectral acceleration (Sa) values are found higher than the Indian code in the period range of 0.1–0.4 s (one to four storey buildings) for Near Field Eq. Scenario. 1. Introduction Large earthquakes that have occurred in recent years in densely populated areas of the world dramatically highlight the inadequate structural designing of the buildings including consideration of near surface ground motion amplification due to soil. The Gujarat state of India falls under three seismic zones V, IV, III of the seismic zoning map of India, Bureaue of Indian Standard [6] with likely earthquakes of magnitude 8, 7, and 6, respectively. The state is one of the most seismic prone regions of the world. It has experienced two large earthquakes of magnitude Mw 7.8 and Mw 7.7 in in 1819 and 2001, respectively and seven earthquakes of magnitude about Mw 6.0, during the past two centuries. The devastation due to Mw 7.7, Bhuj earthquake of 2001 has been observed at distances of upto 300 km. This earthquake is the first major earthquake to hit an urban area of India in the last 50 yrs. During the 2001 Bhuj earthquake, the medical facilities were also disrupted in the epicentral zone (due to fall of main Bhuj Civil Hospital). Gandhinagar is one of the most important city of western India and is the capital city of Gujarat state. It is situated 32 km NE from Ahmedabad. Gandhinagar is a well-planned city divided into 30 sectors. The city is covered with Government buildings like State Assembly (Vidhan Sabha) Udhyog Bhavan (Business governance house), Mahatma Mandir (an International convention center) and economic- ally important structures like Thermal Power Plant, Infocity (a hub of IT sector) and Civil Hospital. A metro connecting Gandhinagar to Ahmedabad is also been planned. Gandhinagar falls in Zone III on the seismic zoning map of India [6]. An earthquake of magnitude Mw 5.7 occurred 100 km south of https://doi.org/10.1016/j.soildyn.2018.03.007 Received 15 September 2017; Received in revised form 24 February 2018; Accepted 7 March 2018 ⁎ Corresponding author. E-mail address: kmohan@isr.res.in (K. Mohan). Soil Dynamics and Earthquake Engineering 109 (2018) 354–370 0267-7261/ © 2018 Elsevier Ltd. All rights reserved. T