I was just thinking - I think the term has also been used to describe seismicity resulting from the motion of glaciers. In all honesty I don't think seismologists have provided a definition for the word as used in seismology. If it is used to describe simply long-duration seismicity, even along fault planes (such is in my surmised "slow earthquake explanation, and in subduction zone movement which just happens to be slow), without the requirement to be non-double-couple, then I think the term is just being used loosely, even by experts.

M.

M.