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Abstract: The strong ground motions at a particular site played an important part from the point of view of seismic hazard estimation. For this purpose, various methods/techniques are present in the seismological literature. A hybrid technique, based on the composite source model and envelope technique has been modified in the present research to simulate the ground motions for an earthquake at the surface level. For modifying the technique, the effects of high-frequency parameter kappa (κ) and empirical transfer functions have been included in the hybrid method. The reliability of the modified hybrid technique has been confirmed by modelling the empirical accelerograms of the 2011 Sikkim earthquake (M6.9). The empirical transfer functions have been computed by the use of observed data of the earthquake. The causative fault of the earthquake has been identified by simulating the accelerograms considering both the nodal planes separately. The essential parameters of the strong ground motions are peak ground acceleration (PGA), duration of the accelerograms, response and Fourier spectrum of simulated accelerograms have been found consistent with recorded ones. Based on the comparison between simulated and observed accelerograms, the regression relation for attenuation of PGA and quality factor (Q) for the region have been identified. The hybrid technique modified here is capable of generating realistic simulated accelerograms for future similar earthquakes in the region. These findings might be obliging in preparing seismic-scenario hazard maps of the region required in the mitigation plans. Article Highlights:

Hybrid Technique is modified by introducing the high-frequency parameter (kappa) and empirical transfer function.

Modified Hybrid technique is used to model the empirical accelerograms for 2011, Sikkim Earthquake (Mw6.9).

Constrained the attenuation relation of PGA and frequency-dependent Q-relation for the Sikkim Himalaya region.