Hi Chris. Here is a short list of quakes that appear to have been south of the equator. No specific locations. It does appear that the 1797 quake occurred to the north of the 1833 quake. I find it rather interesting that all of these quakes occurred within a 64 year period. That is an average of one quake every 16 years. We know that average went out the window with the recent M>8.7 quake. Take Care…Don in creepy town

Since 1900 and prior to the December 26 earthquake, the largest earthquake along the subduction zone from southern Sumatra to the Andaman Islands occurred in 2000 and had a magnitude of 7.9. A magnitude 8.4 earthquake occurred in 1797, a magnitude 8.5 in 1861 and a magnitude 8.7 in 1833 . All three ruptured sections of the subduction zone to the south of the recent earthquake. Interestingly, the 1797 and 1833 quakes are believed to have ruptured roughly the same area with only 36 years separating the events. Paleoseismic evidence shows that great earthquakes or earthquake couplets occur about every 230 years

1797/02/10 Central part of the western Sumatra. The quake was most felt near Padang and in the area within +/-2 deg of equator. Padang was flooded by powerful waves. More then 300 fatalities.

1833/11/24 South coast of the western Sumatra, estimated rupture from 1 S to 6 S latitude. Huge tidal wave flooded all southern part of the western Sumatra. Numerous victims
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1843/01/05 Strong earthquake west of the central Sumatra. Terrible wave came from the south-east and flooded all the coast of the Nias Island. Many fatalities.

1861/02/16 Exceptionally strong earthquake affected all the western coast of Sumatra. Several thousand fatalities.

http://66.102.7.104/search?q=cache:T7_HJiPL71UJ:www.geo.uib.no/seismo/quakes_world/Sumatra-2004/EQ-info/SEQ-Info.html+1797+Sumatra+earthquake&hl=en

http://www.gps.caltech.edu/%7Esieh/publications/a10.html