>
> The sense (polarity) of motion of the phases recorded at a seismic station 
> can be used,

I thought that sometimes the strike-slip as being like dragging a bow 
acrossed a violin string as the sides of the fault "bounce" along while the 
reverse and normal faulting are more like to being  like breaking a limb off 
a tree. I thought I had seen some "stepping" of P on some of the earthquakes 
off the west coast...my imagination? 
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