PEER has just published Report No. 2018/04: “Capturing Directivity Effects in the Mean and Aleatory Variability of the NGA-West2 Ground-Motion Prediction Equations.” It was authored by Jennie A. Watson-Lamprey, Slate Geotechnical Consultants.
We expect there to be locations around a rupture that experience both positive and negative directivity effects more than others. The concept was to develop a simple model of additional mean and standard deviation to add to existing published ground motion prediction equations to account for this. The directivity effect predicted by Chiou and Youngs  using the directivity parameter DPP [Spudich et al. 2013] was selected as the basis for the model. A suite of rupture geometries for strike-slip and reverse ruptures was generated and the mean and standard deviation of the change in the 5% damped pseudo-spectral acceleration at sites out to rupture distances of 70 km was calculated. Models are presented for the change in mean and standard deviation for both strike-slip and reverse ruptures that use only simple parameters as inputs.