Buildings and structures are designed for various forces including those arising due to dead load, live load, wind load, seismic load, etc. Among these, seismic load is generally defined for structures by the national standard based on the seismic zone in which the facility (buildings and structures) is located. Based on this generic seismic load, seismic forces are calculated depending on the importance factor, response reduction factor, time period of structure, and soil properties. Soil properties (shear wave velocity, damping properties, and stiffness degradation) play an important role in the propagation of seismic waves and vary widely both spatially and along the depth. Specified design peak ground acceleration (PGA) value at the bedrock level gets significantly altered by the influence of the local soil site. Further, the zone factor is also an important part in the evaluation of seismic forces which is specified based on different cities or regions of the country. However, the generic zone factor might not give the true picture for megacities like Mumbai that are near one or more fault lines (e.g., for Mumbai: West Coast, Chiplun, Koyna-Warna, etc.), and would require additional attention. In this context, this study first carries out a PSHA analysis for a few eastward locations in Mumbai based on available data from the literature. This will show the limitations as well as the effects of considering a single PGA for a megacity. Next, ground response analysis has been carried out in DEEPSOIL® through the equivalent linear method of analysis using synthetic/scaled real-time ground motions at different sites with different soil profiles. Finally, the work has been extended to observe the effect of uncertainty arising due to limitations in modeling shear modulus value by empirical correlation, over the ground amplification factor.
