@Setanta,
The louisiana Gazette and Advertiser speculated in its 12/21/1811 issue that the comet in view at the time[there was one weve named (C/1811-F1)] was past perihelion nd moving far field West. The papere stated that "PERHAPS" the comet scraped the mountains of California and that impact triggered the earthquake. The newspaper article posed the thesis that earthquakes were ALWAYS products of mountainous regions and since this area(NMSZ) was flat, the author felt that by having a comet hit a mountain in faraway California,this would make enough sense as to trigger an earthquake. Remember the time we were in, there wasnt a big wealth of tectonic savvy.
Tecumsehs brother ( given name of TENSKWATAWA) was a "recovering alcoholic" who began having visions (a few of which actually came true). Tecumseh saw an opportunity to "Use" his brothers visonary skills and parlay that into leadership roles. Youre right, he was Shawnee but the Shawnee actually shunned him (AS DID THE 5 CIVILIZED TRIBES)
Tecumseh was "away on a business trip" and his brother, who apparently had begun to slip back into bad habits, lost the battle of Prophetstown at Tippecanoe and so Tecumseh took over the leadership until his own death.
I submit that Tenskwatawa and Tecumseh were guilty of hubris and , after the 1812 war, all the later Indian "prophets" began to lose face especially since there was no British ARmy to back them up.
Tecumsehs prophecy about New Madrid was as vague and nonspecific as anyone of Nostradamus' predictions. SOmehow, (since his predictions were made in 1806) when the New Madrid occured, everyone would say "Yeh thats what he was talkin about" His cache with the Choctaw Chippewa,Chickasaw , Cherokee and Seminole then went up in value. BUT, I reread my Tecumseh references and found only his andTenskwatawa's statements about a great fiery cataclysm of the earth", but no real references to any comet or meteorite.
Chief Harkins letter referred to Tecumsehs predictions in a sense that he was giving some historical context for the great forced departures due to the IRA nearly 25 years later.
I think Im satisfied that we have another fact-free claim by someone who is passionate about their worldview.
Im also satisfied that, many times passion can get in the way of reason and analysis.(Thats just my humble opinion)