EOS, the weekly publication of American Geophysical Union (AGU), May 31 2005, has an article on the March 28 M8.7 Sumatra quake as an aftershock of the M9.3 But, they go farther and say "If the same mechanism that grows to the the size of a main shock, were to apply farther south on the former 1833 Mw8.7 event area, the next Indonesian Big One may be expected to occur there within a few months"
But, readers may want to emphasize the "If"....big If. This is pretty much the same thing I said on this page a month or so ago. I can't link to this article...you have to login as a member (www.agu.org......publications....EOS).
See my post below on Lynn Sykes, 1960 Chile earthquake...
Chris