Thanks, David.

Faults don't have epicentres, Iains, but earthquakes do. I haven't ruled out in my mind that surface variations may contribute to some seismic activity, but, unless you can provide direct evidence to the contrary (as opposed to speculation, interesting though it is), I'm sticking to my view that almost all non-trivial seismic events are caused by tectonic movements in the crust related to convection in the mantle. And do desist from your silly tendency to cast aspersions on other people's knowledge. There are times when you demonstrate that you're not always the sharpest knife in the drawer yourself.