[X] My Assistant

[edstrick]

Intraplate activity can be wildly variable, from near zero in central texas, to recurring isostatic uplift (post glacial rebound) quakes in Illinois and Western NY, to "anomalous" patches like Charlestown, or the New Madrid Fault zone in the lower Mississippi valley.

So I don't know if they were "averaging" all that sort of variety into a "lump sum" or not, but I suspect so.

The Viking seismometer gave us the data to design an instrument that's good enough to do the job whenever we get around to it.

When I was grad-studenting in St. Louis, there was a Richter 4.2 or so quake in central Illinois. In my apt, it felt like a really heavy truck was driving by where one wouln't drive at all. Glasses in the kitchen cabinet made little jingling noises against each other. It faded away after some 5-7 seconds, then came back for a second wave of shudder-tinkle, then faded away. I presumed P and S wave arrivals.

Later, on the local radio, came a cute story. Father was being pestered by kids to get a puppy. He, totally against the idea, said they'd get a puppy when they had an earthquake in St. Louis. The gods must have been listening......

They named the puppy Richter.

[Guest_BruceMoomaw_*]

Well, that's certainly true -- the most gigantic earthquake in modern North American history, after all, occurred smack in the middle of the North American plate. But I was referring to average intraplate levels, which are undeniably a lot lower than those on plate edges.

[dvandorn]

Ah -- you refer to the quake along the New Madrid fault, back in the 1800s, which moved the then-capitol of Illinois from Illinois into Missouri?

I kid you not -- the capital of Illinois was Kaskaskia, a port city along the Mississippi River. The legal definition of the border between Illinois and Missouri was the river itself; the center of the river was (and still is) the state line. The quake caused the river to re-route itself into a topographic low (that it had probably already flowed through once, eons ago) and moved the river from the west of Kaskaskia to the east of most of the town. The center of the town was literally inundated in the new river's path.

Fairly shortly after this event, the capitol of Illinois was moved to Centralia, which, as its name implies, sits right in the center of the state. It was another couple of decades before the capitol was finally moved to its current location, in Springfield.

But that quake is still the only one I've ever heard of that moved a state capitol into a neighboring state!

Sorry for the off-topic post, but it seemed to fit here.

-the other Doug

[edstrick]

I just love "Factinos" like that. They're fun.
Note that's a Factino, not a Factoid, which is something that looks like a fact but ain't!