Read this:
Within minutes following an alarm signaling the strong earthquake, the NOAA Pacific Tsunami Warning Center in Hawaii issued an information bulletin to nations in the Pacific at 8:14 p.m. EST Saturday, indicating that a magnitude 8.0 earthquake (later upgraded to magnitude 9.0) had occurred off the west coast of Northern Sumatra, Indonesia. Because the earthquake, reported to be one of the strongest in the world (snip)
Found here: http://www.noaanews.noaa.gov/stories2004/s2357.htm
Computer animation that was made and SENT with the report:
http://www.noaanews.noaa.gov/video/tsunami-indonesia12-2004.qt
Made from mapping an 8.0 earthquake that was later UPGRADED to 9.0
The warning went out based on 8.0
So what? The countries hit, for the most part, didn't have a tsunami warning network. Some, like Thailand, made a decision not to issue an alert "as a courtesy to the tourist industry" (their words)...