Hi Todd,

Yes, seismic tremor is a different phenomenon than waves produced by earthquakes (except maybe a "slow earthquake, with duration of hours to days[?] produces them . . .) I was going to refer you to a source to give a more complete and accurate explanation, but, surprisingly, in a short search I couldn't find one. I DID discover a band named Seismic Tremor!

Here's the best I can do. Use at your own risk:

The term is most often used to describe the type of waves, non double-couple, that are produced by magma moving underground, but, in this case of the SAF, and in a few others, that is not always true. IIRC tremor has also been associated with subduction zones (I think Michael T.'s article referenced that), and with the aforementioned "slow earthquakes". I think the term was originally almost exclusively used for volcanic purposes, and has since been broadened, as new phenomena have been discovered, to include other sources of relatively long duration and without the double-couple component which results only from movement along a fault plane.

Mike W.