Glen,

According to me, every quake formation there is a fresh precursor. Recently I have come across details of a great quake,
for which 7.2M foreshock triggered before a main shock of 8.5M! (If I do remember correctly - may be at Chile). In this case
if we cross our hands after the 7.2M quake thought that it was the main shock and looking for a aftershock of reduced magnitude,
we are in trouble. So whatever precursor I received and wherever be the location, I would count it as a fresh shock.

Normally after a strong quake, mild to moderate quake may be witnessed on the same location due to settlement of earth at the
particular place which will not produce any advance precursors. Otherwise, it have.

Shan