Friday, April 18, 2008

Mag 5.2 Earthquake in the Midwest, 5:37 AM EDT,

5:37 AM, local EDT time. I was awake early and felt it. It rumbled for a few seconds, built up, and then the building shook, then died down to a rumble. It lasted maybe 7 to 12 seconds.

I started to call the TV stations but their lines were busy.

Here's the detail from US Geological Survey.

Here's the map from the US Geological Survey.

It's on the WABASH FAULT, which runs along the border of Indiana and Illinois, and is also associated with the Wabash river. The Wabash Fault zone is north of the New Madrid fault zone. There is debate in the geological community as to how closesly associated or connected the Wabash fault zone is with the New Madrid fault zone. The New Madrid fault was the location of huge magnitude 7 quakes in 1811 and 1812.


Update: The USGS has re-classified this as a 5.2 magnitude quake, after originally publishing it as 5.4.


Update: Several aftershocks later in the day. First aftershock was 4.6, then some smaller ones.



At 4/18/2008 07:05:00 AM, Blogger Eric Nielson said...

I live in southern Michigan and felt this quake also. I asked my wife if this is a divers place.

At 4/18/2008 08:43:00 AM, Anonymous Anonymous said...

Welcome to our [western] world, Bookslinger /g/. Any signs of the Mississippi reversing its course, the way it did in 1811? I haven't heard the story on local news yet, and hope there was no appreciable damage.

At 4/18/2008 10:36:00 AM, Blogger kristine N said...

Ardis--there wasn't any appreciable damage. I felt it in West Lafayette--in fact, I was thinking as it was going on that I was in the wrong state for this! It's very exciting.

The 1811 earthquake was an incredibly strong earthquake. Fortunately unlikely to happen again.

At 4/18/2008 10:38:00 AM, Blogger Bookslinger said...

Very little damage. As of 8:00am, the only damage reported on the TV was part of the facade on an old building in downtown Louisville KY that came off.

To describe it more, here in Indianapolis, I felt three parts: first was the rumbling build up, like when a freight train goes by and you're near it, then there was the big part of shaking and creaking of the building, then the let-down which was the freight-train like rumbling again.

Nothing got knocked over. I don't know if the movement was up-and-down, or swaying side to side. But I'm thinking more up-and-down.

I was still in bed, but had woken up about 10 minutes prior to the quake.

It's been reported that people traveling in cars could not feel it. Also, many people who were awake and sitting did not report the build-up and let-down, just the 4 or 5 second main shake. My origianl estimate was 10 seconds including the build-up and let-down.

USGS has revised the magnitude to 5.2 (down from 5.4).

The local news anchors said that the local effect of this quake, as felt in Indianapolis, would be the same as if we had had a magnitude 3 right here.

Last I felt a quake in Indianapolis was some minor vibration in the summer of 1988.

At 4/18/2008 11:30:00 AM, Blogger kristine N said...

We just felt another one in West Lafayette. We've go a seismograph hooked up in the building (it is a geology department, after all) and it looks like the most recent one was about the same magnitude as the earlier one.

What you felt in Indy was about what I felt in West Lafayette. It's amazing how far the seismic waves are able to propogate out here in the midwest. If this were California or Utah, you'd be unlikely to feel it because the crust is so much more deformed and so much warmer. Of course, sitting on a few hundred feet of glacial till probably doesn't hurt us here either...


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