Seismic Site Characterization Using Earthquake HVSR Modelling in the Eastern Chhotanagpur Plateau, India

We have used the Horizontal-to-Vertical Spectral Ratio (HVSR) method to analyze earthquake recordings from six broadband seismic stations in the Eastern Chhotanagpur Plateau, India, to investigate its subsurface characteristics. The stations’ fundamental resonance frequencies (f0) vary from 4.5[Formula: see text]Hz (at Peterwar) to 14.3[Formula: see text]Hz (at Nirsa), suggesting differences in sediment thickness and impedance contrasts. The presence of three discrete subsurface layers is indicated by the shear wave velocity profiles (Vs), which range from ∼90[Formula: see text]m/s to ∼260[Formula: see text]m/s, ∼210[Formula: see text]m/s to ∼990[Formula: see text]m/s, and ∼860[Formula: see text]m/s to ∼1500[Formula: see text]m/s for the upper, middle and bottom layers, respectively. The results emphasize regions with a high potential for amplification, particularly in sites that exhibit directional HVSR variations and strong impedance contrasts. The azimuthal HVSR analysis indicates substantial anisotropic effects at seismic stations in Dhanbad, Khunti, and Peterwar, implying complex subsurface strata and lateral heterogeneities. The comparison of inverted Vs profiles with Standard Penetration Test (SPT) and Electrical Resistivity Tomography (ERT) data at the location of seismic station at Dhanbad validates the accuracy of the HVSR-derived shear wave velocity models. These results offer crucial insights into regional hazard assessment, seismic amplification, and local site effects, thereby facilitating the development of earthquake-resistant infrastructure for national agencies such as the National Disaster Management Authority (NDMA), state disaster management, and the Geological Society of India (GSI).