On the second site (ATS), people debunk the myth that El Hierro would cause a tsunami if you read far enough into the thread. Why? For the above reasons.
So Again...WRONG ISLAND.
Actually you could not be more wrong.
http://geomar.geo.ub.es/eurodom/documents/Massonetal01_ESR.pdf
Errant, if you have not read this paper yet, you will find it very comprehensive.