Illinois earthquake

[I'm Still Bison]

 Any of our members experience this one? Tremors were felt in my area,about 350 miles east of the epicenter.This was close to the New Madrid faultline..I seriously hope that's one faultline that's not waking out of dormancy.

http://news.yahoo.com/s/ap/20080418/ap_on_re_us/midwest_earthquake

[Mike, Lord of the Spammers!]

Best of luck to all those involved.

[edap617]

Is the epicenter far from the San Andreas fault?

[NutSAK]

Yes!  I woke up startled at 4:38am this morning, to my house shaking.  I'm about 150 miles from the epicenter, and it was the strongest quake I've felt yet.  I live very close to the New Madrid fault near the eastern border of Missouri, but this one was from the Wabash fault, on the eastern border of Illinois.

It wasn't strong enough here to cause any damage, but it certainly was an eye-opener.

[I'm Still Bison]

Eddie, the San Andreas fault is in California,and this morning's quake is almost dead center in the US,in an area that for almost 200 years,has been almost geologically boring,,which is what makes this one such an eye opener.

[NutSAK]

One thing that many people don't realize is that an earthquake in this part of the country has the potential to cause much more widespread destruction than an equal-strength earthquake has around the San Andreas fault.  The bedrock  here in the Midwest is much more solid, and the shock waves set forth from the epicenter can therefore travel much greater distances without losing strength. In California, where the bedrock is broken up from tectonic plate upheaval/subsidence and frequent earthquakes, that energy can dissipate over shorter distances of travel.  Case in point--a 5.4 magnitude earthquake like this is fairly minor, yet people who live 250 miles from the epicenter easily felt it.

[EM745]

One thing that many people don't realize is that an earthquake in this part of the country has the potential to cause much more widespread destruction than an equal-strength earthquake has around the San Andreas fault.  The bedrock  here in the Midwest is much more solid, and the shock waves set forth from the epicenter can therefore travel much greater distances without losing strength. In California, where the bedrock is broken up from tectonic plate upheaval/subsidence and frequent earthquakes, that energy can dissipate over shorter distances of travel.  Case in point--a 5.4 magnitude earthquake like this is fairly minor, yet people who live 250 miles from the epicenter easily felt it.

(Uh-oh! You just woke the "Discovery" geek in me  .)

It is true that solid bedrock will propagate a tremor's energy over larger distances (much like sounds waves travel farther underwater than in less dense air). But given equal Richter values, it will not cause more destruction (widespread or not). On the contrary, quakes that occur over looser bedrock tend to be far more destructive, even though the damage will be less widespread. Loose bedrock is like jello, amplifying the quake's energy through "wiggling," harmonics and such. With solid ground, that energy is, like you said, dissipated over a much larger area. This means that while a lot more people feel it, the effects are less "destructive," even for those nearest the epicenter. A 6.0 under loose ground will be far nore destructive than a 6.0 under solid ground. With the latter, the damage (if any) will be more widespread, but far less severe than the former.

Solid bedrock is also partly why quakes in these regions occur far less often. The stress can build up over larger periods of time between each "release" (quake). With looser ground there doesn't need to be as much build-up of geological stresses before tectonic movements occur... so quakes tend to be for more frequent, like in CA (or course, lying smack-dab on the Ring of Fire doesn't help either).

[NutSAK]

All very true.  Note that I said, "more widespread destruction".  I didn't say "more destruction".

The point that I was trying to make is that the waves can travel farther, not that they will cause more destruction in any given area.

BTW, we just had a small after-shock a couple of hours ago, in the 4.0 range.

[WhichDawg]

wow, I can't believe it (I do but still) I just moved from near regular Salem Illinois last summer,
(which is west of the epicenter by about 20 mi) I bet my cousins woke up to that!

[Mike]

We on the west coast, I'm in Washington State do pay close attention to any and all earthquakes. I'm just glad it wasn't worse and that nobody (I think) was injured.

Sometimes I get the feeling we are on the edge of something big and bad. Be it man-made, or mother nature, just seems like all hell is on the verge of cutting loose. Maybe I worry too much.

Mike

[Mike, Lord of the Spammers!]

We on the west coast, I'm in Washington State do pay close attention to any and all earthquakes. I'm just glad it wasn't worse and that nobody (I think) was injured.

Sometimes I get the feeling we are on the edge of something big and bad. Be it man-made, or mother nature, just seems like all hell is on the verge of cutting loose. Maybe I worry too much.

Mike

Nope I feel the same mate, and I wouldn't consider myself a 'apocalyptic' nut

[NutSAK]

wow, I can't believe it (I do but still) I just moved from near regular Salem Illinois last summer,
(which is west of the epicenter by about 20 mi) I bet my cousins woke up to that!

I thought I remembered you mention that a couple of weeks ago.  Good thing you aren't there anymore, you would have at least been out a set of dishes! 

[WhichDawg]

and I thought when I moved here I was gonna feel them!

[WhichDawg]

we just found this article; http://news.nationalgeographic.com/news/2008/04/080416-oregon-quakes.html
maybe I will feel them!

[Smitty44]

Thats just a little to close to us in the Mid West,just a couple hundred miles east, but 5.2 is to big for this area,it's already bad with the blizzards,ice storms,floods,dust storms,and tornado's !!!