[John H K]

I did mention that with a really big asteroid you could perhaps get above 10.

Obviously no accurate measurement at the time, but certainly none of the New Madrid quakes were over 9, and I've seen a few papers revising the estimates downward under 8 so that they're no longer the largest continental US earthquakes.

The "Ring of Fire" has never gone off all at once, or anything close to that, so I'm not sure what you're talking about there.

The Deccan Traps were a large-scale volcanic event, but not an instaneous one, that outflow was still over a period of years.

The point is energy is a matter of physics, and you can't generate a 10+ without the sufficent fault surface to do so; You'd need a fault encircling the globe all going at once, and there's nothing like that, or remotely like that, on earth.

[boris]

"The "Ring of Fire" has never gone off all at once, or anything close to that, so I'm not sure what you're talking about there."

I saw an article in Scientific American some years ago which discussed the entire Ring of Fire going off with a periodicity of ~100,000 years...or that's my recollection.

Thank you for correcting my "Steps" to "Traps"; I had forgotten the correct term.

Are you a professional geologist or geophysicist? I have a question for such a one.

--Boris

[capitan_refugio]

As I recall, there were three large events associated with the New Madrid sequence. Since these happened during the winter of 1811-1812, there were obviously no scientific measurements. However, accounts of the earthquakes suggest that they were "continental" in nature ("rang church bells in Boston," etc.). The pattern of desturction suggest quakes on the highest level of intensity (Mercalli XII).

I have relative in western Tennessee and have seen the "ghost forests" at Reelfoot Lake. Purportedly, the lake filled an earthquake-formed graben, by diverting the flow of the Mississippi River. Contemporary accounts have the part of the river just down stream from Reelfoot Lake flowing BACKWARD overnight to fill the newly-formed low ground. Just a review of topographic maps of the area suggest that this was entirely possible.