Strong ground motion parameters of the 18 September 2011 Sikkim Earthquake Mw = 6.9 and its analysis: a recent seismic hazard scenario

The 18 September 2011 earthquake in Sikkim was one the most devastating earthquake in Sikkim Himalaya in India–Asia collision boundary. The source characteristic of this earthquake is associated with NW–SE-directed strike–slip Tista fault. This particular event killed around 60 people and damaged a number of civil engineering buildings in and around Sikkim Himalaya due to strong ground motion parameters evolved out of this event. These typical strong ground motion parameters are estimated utilising the accelerograms recorded by a network of seven stations existed in the region. The highest PGA and predominant period pertinent to main event are observed at Gezing. In spite of PGA being lowest, severe damage occurs in Gangtok city. The distribution of estimated maximum acceleration and predominant period characterise the site of the region. Simultaneously, the estimation of Fourier spectra, power spectra, response spectra and the attenuation curve depicts the site-specific condition and its contribution to the ground motion parameters inferred so far. These estimations lead to the understanding of the damaging ground motions produced due to the main shock for developing better methodology for seismic hazard assessment and mitigation in Gangtok city and its vicinity.