Seismic Hazard Assessment | Department of Civil

Seismic Hazard Assessment

Seismic hazards during many disastrous earthquakes are observed to be aggravating at the sites with the soft soil deposits due to amplification of ground motion. The characteristics of strong ground motion, the site category, depth of the soil column, type of rock strata, and the dynamic soil properties at a particular site significantly influence the free field motion during an earthquake. Stochastic finite-fault simulation combined with site response analysis is used to understand the spatial distribution of ground motion due to damaging earthquakes.

Stochastic finite-fault simulation combined with site response analysis is used to understand the spatial distribution of ground motion due to damaging earthquakes. The rock level ground motion for the scenario earthquakes is generated based on the stochastic finite-fault methodology. These simulated motions are further amplified up to the surface by nonlinear site response analyses using the available soil profile data at several locations in the study area. Based on these simulated free-field motions, site correction factor is obtained for each soil site, which is useful in identifying vulnerable places in the study area. 

The susceptibility of soil liquefaction is studied using the ground motion at different depths obtained from nonlinear site response analyses. The liquefaction susceptibility is quantified in terms of the factor of safety along the depths of the soil column at available borehole locations using earthquake-induced cyclic stress on the soil and the cyclic resistance of the soil to withstand the load. Liquefaction potential index (LPI) is evaluated at the site of interest from the obtained factors of safety (FS) to predict the potential of liquefaction to cause damage at the surface level.