The localization of seismic events in space and time has great importance for hydro fracturing and reservoir monitoring. A new passive seismic localization technique by diffraction stacking has been introduced recently. Method has many advantages due to a performance by a modified diffraction stack of the squared amplitudes of the input seismograms resulting in the image section. The source location is obtained from the maximum of the image section. The source time is determined after source location in space. Energy is stacked during the procedure hence very weak events against the background noise could be located. Numerical 2-D tests with high-level synthetic noise give visual confirmation. Another numerical example representing the scattering overburden over homogeneous medium provides great possibilities in application to the real data which is major issue to be solved. In case of badly known velocity model additional stacking over velocity range can improve the result.