A scenario of ground shaking hazard in intracratonic circular basins developed by basin-generated surface waves: an earthquake engineering perspective

This paper presents the comparative scenario of ground motion amplifications in the 2D semi-cylindrical (SC) basin and 3D semi-spherical (SS) intracratonic basin caused by the basin-generated surface (BGS) waves and the associated spatial variations of average spectral amplification, differential ground motion (DGM) and average aggravation factor (AAF). The time-domain seismic responses of both the basins were computed using a recently developed 3D fourth-order accurate viscoelastic finite-difference algorithm based on the well-known GMB-EK rheological model. The analysis of simulated results revealed that AAF and DGM are comparable near the basin-edge in both the basins but the differences are increasing towards the centre of basins due to the focusing of the BGS-waves in the SS-basin. The obtained many-fold increase of 1D/2D-AAFs and DGM at the centre of the SS-basin as compared to the SC-basin reflects the inadequacy of 1D or 2D response of an intracratonic circular basin for the seismic hazard assessment. It may be inferred that the level of damage near the edges of the 2D and 3D circular basins may be comparable but unexpected damage may occur in the central part of a circular basin due to the focusing of the BGS-waves.