WATCH & LISTEN: The Scary Secret About the Lower Northwest
Earlier this month, there was a series of earthquakes that struck California, but there are also ones that tend to hit closer to home.
The closest fault to us is New Madrid. Samantha Reif is a geology professor at Lincoln Land Community College.
”You may think that, oh we live in the middle of the country, no big deal, but there is a pretty big fault line that runs along the Mississippi River. So that can cause some pretty sizeable earthquakes. Is it as dangerous as California, probably not, but it’s still something to be aware of,” said Rief.
The New Madrid is unique in many ways. It's not a normal fault line, such as the ones in California.
”But at some time in the past billion and a half years ago or so, North America started to pull apart right in the middle. Right where the New Madrid is today,” said Reif.
”So North America didn’t fall apart here, but there is this big rip in the middle of it and that is the New Madrid fault,” said Rief
That becomes a problem, because North America does not stay still on the earth. It moves around and the continent is rotating very slowly counter clockwise.
“So, it’s kind of rotating, and this spot right in the middle is kind of like if you take a piece of paper and you rotate it but you hold the piece in the middle still. It starts to bunch up and wrinkle. So the New Madrid is kinda this wrinkle,” said Rief.
In fact, if you dig down to where the fault is you can see the rocks bunching up. When the rocks bunch up like this, they’re under tremendous stress from the movement of the rock around it. This can be dangerous if it’s not releasted.
”It’s taking in energy. It’s taking in this kinetic energy, so this energy builds up and builds up and builds up. Until that stretching that is going to release that energy and is going to cause an earthquake,” said Rief.
So why do we not feel more earthquakes here?
“If you look at any earthquake maps, it does it regularly. We have lots and lots of earthquakes in Illinois. You're usually never going to notice them, and that's a good thing. You want a lot of little earthquakes, because if you have a lot of little earthquakes then you get only a few really big earthquakes,” said Rief.
The last major earthquake in the New Madrid was in 1812, yet scientists do not know how strong it actually was because of a lack of technology.
“In 1812 and 1813 we had some big earthquakes, but we did not have any way of measuring them at the time. And so we estimate based on damage and based on what people talked about. Some of the estimates come in around 7 to 7.5,” said Rief.
The big earthquakes in California earlier this month were a lower magnitude than that, at 6-point 4 to 7-point-1 at most. An interesting fact is that earthquakes can move differently here then in other parts of the world.
”The cool thing about the New Madrid fault is the fact that the fault is buried in the hole basin, which in Illinois means it is covered in dirt. It makes the quake waves move differently and they move farther away from the epicenter then they do in California,” said Reif.
Reif provided some tips on what to do when an earthquake occurs.
“So if you have a big earthquake you are supposed to stay where you are for a while. But once it’s safe, once you know that the shaking has stopped, that there is not going to be a tsunami or any fires because of downed power lines and broken gas lines. Once all of that is confirmed, you need to leave the building you’re in,” said Rief.
In the past there have been multiple big earthquakes so it's better to be prepared for one then to be shocked by one. You can find more information at the United States Geological Survey website which is USGS.org.
This has been Abigail Stalets with NPR podcast academy.