The mainshock-aftershock fragility surfaces incorporating mainshock intensity (IM_M) and aftershock intensity (IM_A) can well reflect the impact of the mainshock-aftershock sequences on the seismic performance of structures. To this end, this paper utilizes a double incremental dynamic analysis (D-IDA) approach to separately scale the mainshock and aftershock and makes use of a stepwise regression approach to generate the probabilistic mainshock-aftershock demand model. With the help of the projection approach, the fragility curves for different values of IM_M and IM_A and the fragility contour lines of structures can be derived. The fragility surfaces analysis framework is illustrated using a typical reinforced concrete frame structure designed conforming to the current standard in China. It is found that the seismic fragility increases with increasing IM_A while the fragility is aggravated by aftershocks. Furthermore, the fragility contour lines depict that a larger IM_M (or IM_A) leads to a decreased IM_A (or IM_M) required for the same damage state, but the mainshock generally causes more damage compared to the aftershock for the same intensity.