Inversion of HVSR Curves using Monte-Carlo Global Optimization Technique for Seismic Site Characterization

Abstract

Summary Shear wave velocity and site amplification study play vital role to reduce the effect of triggered and natural earthquakes disasters. Our study area comes in moderate to low seismic zone of India and low to moderate size earthquakes comes due to mine activity and complex geological settings. To reduce the effect of these calamities we have acquired microtremor data in a linear array of 2 Km profile length at the spacing of 250 m. HVSR curves which is computed by the Fourier transform of microtremor data, is used to estimate the shear wave velocity structure. The shear wave velocity is estimated by the inversion of HVSR curve using Monte-Carlo (MC) inversion technique. We have used guided Monte-Carlo inversion technique which is very stable. The best model of 1D shear wave velocity is interpolated into 2D shear wave velocity profile, which gives the three different layers. First layer having thickness 3–12 m with velocity range 400∼700 m/s. Second layer thickness is about 18 m having velocity range 700∼1150 m/s, this demonstrates the engineering bedrock. Third layer has velocity >1150 m/s. The 2D shear wave velocity and HVSR profile have quite good agreement in terms of impedance contrast. Peak HVSR amplitude range varying in the range 2.77–6.25 and predominant frequency having range of 4.61–10.4Hz.