This has been around for some time now. It is part of the Japanese prediction/mitigation
program, but never been put to a practical test (at least none the Japanese want to
make public).
I wonder what EM and other precursors the VAN group will claim for the Mw 6.3
in the Aegean Sea this evening. While earthquakes of Ml>6 are not uncommon in
this region of the Mediterranean, this is the largest earthquake within 200 km of
this epicenter in the Aegean Sea since August 6, 1983 (18 years ago) when a Mw
7.3 occurred. From the looks of the seismograms, the NEIC magnitude appears
considerably underrated. Probably more like a 6.5-7.0 Ms. Current parameters are:
26Jul2001 00:21:37.5 39.1N 24.3E 10 MW=6.3 M NEI AEGEAN SEA

• NEIS Earthquake bulletin