The New Madrid Seismic Zone is the most significant regional seismic hazard in the Central and Eastern United States. Due to lack of strong motion records, the current practice is to establish seismic source and wave propagation models to generate on-component motions for the seismic design of structures. Moreover, three-component simulations including near-field effects (forward rupture directivity and fling step) at the rock upper surface have recently been initiated based on an equal-weight logic tree using the well-established and validated composite source model. The objective of this study is to perform of sensitivity analysis on different parameters of the logic tree to identify the influence of the uncertainty of each parameter on the resulting motions and their near-field characteristics. These parameters include rupture area, depth to top of fault, hypocenter location along strike and dip, fault mechanism (strike, dip, and rake), rupture velocity, slip distribution, stress drop, and velocity model of the earth crust. The scope of this study includes three sites located within 26.5km from the southwestern segment of the New Madrid Seismic Zone, for future earthquake events of moment magnitude 7.5. the results are used to refine and introduce new parameters to the logic tree.