There's probably just one flavor of non-volcanic tremor, but a range of durations from 1s to several weeks have been spotted. A variant is tremor that pulses with passing large surface waves, but is silent before and afterward.

The symptoms are - emergent beginning, much smaller magnitude for the duration than normal quakes, redder spectrum, generally shows up on the lower edge of regions with normal earthquakes. Activity sometimes is observed to migrate about 10km/day.

So far as we know, the slip is generally double-couple for NVT.