  Compact object mergers are promising candidates for the progenitor system of
short gamma-ray bursts (GRBs). Using gravitational wave (GW) triggers to
identify a merger, any electromagnetic (EM) counterparts from the jet can be
used to constrain the dynamics and structure of short GRB jets. GW triggered
searches could reveal a hidden population of optical transients associated with
the short-lived jets from the merger object. If the population of merger-jets
is dominated by low-Lorentz-factors, then a GW triggered search will reveal the
on-axis orphan afterglows from these failed GRBs. By considering the EM
counterparts from a jet, with or without the prompt GRB, the jet structure and
dynamics can be constrained. By modelling the afterglow of various jet
structures with viewing angle, we provide observable predictions for the on-
and off- axis EM jet counterparts. The predictions provide an indication for
the various features expected from the proposed jet structure models.
