Don,

The accelerating seismicity before earthquakes has only proven identifiable before failure in pristine rocks in the lab. Acoustic emissions are just a way of getting a larger set of seismicity by including cracks down to a very small size, as I understand it.

Accelerating seismicity had been seen after the fact, and termed the Bufe-Varnes something-or-other, and written up by Sornette and Sammis, among others.

The key unresolved questions are (1) whether the volume giving off signals that it is approaching failure is big enough to be detectable (if it is too small we can't spot it) and (2) whether big earthquakes start any differently than small events (small events happen every day, so if we can't tell the difference, we're also sunk).

John