[en] We calculate the effects of the pair production of top quarks and their subsequent weak decays on event topologies and inclusive distributions in e⁺e^- annihilation experiments. The resulting jet distributions are compared with those originating from the lighter quarks (u, d, s, c, b) with higher order QCD corrections included. The calculation is based on the Kobayashi-Maskawa model for the weak decay of the heavy quarks including nonleptonic and semileptonic decay modes. The final evolution of quarks into hadrons has been taken into account using a quark fragmentation model. We find that the jet measures such as sphericity, thrust and acoplanarity are very sensitive to the onset of a new quark threshold in e⁺e^- experiments. A comparison is made with available data from PETRA in the energy range 13 <= E cm <= 31.6 GeV in order to test the model below the t anti t production threshold. (orig.)