The free field surface motion during an earthquake is governed by the characteristics of strong ground motions and the dynamic soil properties at a particular site. The soft soil deposits aggravate the seismic hazard due to the amplification of ground motion at some intensity level. In this article, seismic site response analysis is used to estimate the spatial distribution of surface level free field ground motion at Mumbai city due to multiple suites of input earthquake ground motions, scaled to conform to the target rock level uniform hazard response spectrum with minimum mean squared error. Free-field surface motion is found to be influenced by the softness of soil site and intensity of ground motion. Surface level free field motion due to excitation at bedrock level at each site is quantified in terms of spectral acceleration. Acceleration response spectra at selected natural periods and corresponding standard errors are computed and the results are presented in the form of contour maps. The spatial distribution of ground motion obtained in the form of contour maps will be useful in finding seismic coefficients to determine the design seismic forces and in identifying vulnerable places in Mumbai city. © 2011 ejge.