Piledriving - Point, Line or Moving Source?

We've had a few questions on how to model pile driving. I think it's time to do a post on what sort of source geometry one can use for pile driving. Piles are complex sources as they are not easily characterised as monopole sources (as e.g. an omnidirectional transducer would be). Even seismic arrays can, at sufficient distance, be treated fairly as a monopole source, given its relatively small size compared to the usual operating sites. For piles this is rarely the case, they span the whole depth of the site (that's the point of piles) and emit sound along their whole length when struck or vibrated - more like a line source, or a very fast-moving source (speed equal to compressional wave speed of steel, >5000 m/s). This is the case in theory, but I'm interested in the modelling application of this: Can we safely model pile driving as a point source? What other source geometries might be better suited? I can already say that I'm not going to address "1"

Kurtosis, what's that? A single value to rule them all!?

More deatail please!