Effects of a Magnitude 3.7 quake
On March 2, 2010, 1:37 pm CST, a magnitude 3.7 quake was recorded near East Prairie, Missouri. It's near Charleston, Mo., and Cairo, Il., and 17 miles NE of New Madrid. This is the approximate northeast corner of maps of New Madrid quakes, although some fault lines proceed north and east toward the Wabash area of Indiana.
Typically a magnitude 4.0 starts to get serious. No damage, no injuries from this one. Local windows rattled heavily, but did not break. This report may give you some idea how a larger quake might resonate.
Beating a Big Bass Drum
Most world quakes are at the edge of tectonic plates, where the plates abruptly scrape together. Those quakes usually don't travel far. But New Madrid is in the MIDDLE of a tectonic plate. Scientists are still trying to figure how the rules apply here, but they know the quakes here resonate farther. It's like striking a big bass drum in its center.
On the far reaches, four reports came from people feeling it in the Kansas City area (300 mi), one from north Iowa (450 mi), one from Chicago suburbs (300 mi), one from central Mississippi (300 mi). The distance winner was Salem, Va. (500 mi), just past the Blue Ridge Mountains. Hardly anyone from Memphis area (100 mi) reported feeling it. Almost all said it felt like a "2" on the Mercalli "felt" scale, which goes to 12. Six people in the Lexington Louisville Somerset Frankfort area of central-eastern Kentucky, 200-300 miles away, reported feeling it.
When a magnitude 5 quake struck north of Evansville, Indiana in 2008, it was felt in Canada and New Orleans. The big New Madrid shakes of 1811-12 made people in Knoxville and Savannah feel they were on rough ocean waters. Bottom line: a little goes a long way, here. It goes much farther than in California.
Drum recorders draw a seismogram on a piece of paper wrapped around a slowly revolving drum. As the drum revolves, the pen shifts across it, making a big spiral or helical record that eventually fills the entire page. When the paper is removed and laid flat, the record appears to be many horizontal lines, like lines in a book. Mechanical recorders, popular 30 years ago, have largely been replaced by computers, which digitize the data (typically at 100 samples per second). Computers can still display the data old-style.
Hickman Ky is very near. EACH VERTICAL LINE IS ONE MINUTE OF TIME.
Poplar Bluff is at the north edge of the Bootheel, and the edge of Ozark Mountains. No other "noise" polluted this screen
Lepanto is in NE Arkansas. Spikey images are local shaking "noise".
This is on a farm near Portageville Mo.
Halls is in West Tennessee.
Bloomington is comfortably away in south central Indiana.
These below are in EAST TENNESSEE - where other faults lie. Note that the East Prairie quake seems to last longer here. We offer no explanation. We also don't know what caused the big red blob. Four other east Tennessee seismographs also showed the lingering effect of this quake - seeming to last three minutes instead of one..
Here's how the Feb 27, 2010 massive Chile quake appeared on the Poplar Bluff seismograph.
Reading the Seismograph: P waves, S waves
Bill Emerson Bridge at Cape Girardeau
The 4,000-foot Bill Emerson Memorial Bridge across the Mississippi River at Cape Girardeau is 50 miles from the epicenter region of the 1811-12 quakes. It opened in 2003.
It has 84 channels of accelerometers. Of those, 66 are on the bridge. The data flows by broadband.