Earthquakes? In Oklahoma? It's more likely than you think.


This is a picture of Meers Fault in southwestern Oklahoma—the only place in the state where tell-tale signs of earthquakes are visible above ground. But, beneath the surface, the Sooner State is riddled with faults—far more than anyone could count, says Andrew Holland, seismologist for the Oklahoma Geological Survey.

Those faults are behind the moderately sized earthquake that struck near Norman, Oklahoma, yesterday morning—somewhere between 4.3 and 4.7 on the Richter scale. Thirty miles North, in Oklahoma City, it rattled my Dad's windows and scared the crap out of his cats.

I always knew earthquakes were possible in the lower Midwest, raised, as I was, on tales of the massive one that shook New Madrid, Missouri, in 1812. But I didn't realize that Oklahoma—and Kansas, and Arkansas—also had active faults. In fact, 2010 has been a banner year for Oklahoma earthquakes. More than 80 have been recorded, and more than 50 of those were felt by people—far above the state average.

I called Holland to find out why there's so much shakin' going on, whether this has anything to do with the infamous New Madrid fault, and how you get a fault in the middle of a tectonic plate, to begin with.


Maggie Koerth-Baker: I think most of us are used to the idea of faults being found at the edges of tectonic plates, but Oklahoma is right in the middle of the North American Plate. Why would you find faults there?

Andrew Holland:

Oklahoma has been pulled apart and stretched over previous cycles of plate tectonics. There are spots where the North American Plate has been pulled apart and where old plates fused together. The fault lines still exist in the subsurface. They're buried. But they're under a lot of pressure. You get transferring pressures from the plate boundaries at the Mid-Atlantic Ridge and the Pacific and San Juan plates on the other side. There's these pressures from the edges that get transmitted through the solid rock.

MKB: How are these faults different from what you'd find in, say, California?

AH: The rocks here are older and less deformed on the edges. They're stronger than they are in California, where things are actively deforming. So, here in central U.S., the energy from an earthquake gets radiated much further than in California, because the rock the seismic waves travel through is more solid. It's just like how sound carries faster and louder through metal, than through wood or Styrofoam.

MKB: If these faults are buried in solid rock, how do they move? I can easily picture how a fault at the edge of a tectonic plate builds up and releases energy, but how does that work in Oklahoma?

AH: The sense of motion on our faults in Oklahoma is actually very similar to the motion in the San Andreas. Imagine two bricks sliding past one another. It's harder to imagine, even for me, how you have this slip at depth. But it's basically two rocks sliding past one another.

MKB: The recent earthquakes in Oklahoma aren't being caused by the New Madrid fault, correct? Are they similar faults, though?

AH: It is correct that these earthquakes are occurring on faults unrelated to the New Madrid fault. It's a different fault, but similar in style. There's a bigger demonstrated hazard on the New Madrid fault, but we do have possibility of having a larger earthquake in Oklahoma. There's one fault here that's actually visible from Google Earth, the Meers fault. We can look at the geologic record and see that it was active about 1300 years ago, with a couple episodes equivalent to magnitude 6.5.

MKB: How common are earthquakes in the lower Midwest? It seems like we're always shocked when they happen, but Oklahoma actually has some almost every year, right?

AH: It's more common than people think. In Kansas, my wife's parents carried earthquake insurance on their house in Junction City their whole lives. Arkansas is having earthquake swarms right now, too. It's funny, I go around and older people remember feeling the 1952 'quake. That's the largest we've instrumentally recorded in Oklahoma—somewhere between 5.2 and 5.9. I think people are surprised, though, because it's less common than in California. People have short memories and we have tornadoes every year, so those stand out more.

MKB: This year, and 2009, have been peak years for earthquakes in Oklahoma. Do we know why that increase suddenly happened? Is this weird?

AH: This year is a statistical anomaly. But we've got catalogs all the way back to 1897 and there's basically been earthquakes in all but three counties in Oklahoma. We don't know for certain what triggers peak years. Could just be random chance, the statistics playing out. One thing, that's somewhat applicable here ... if you look at the North Anatolian Fault in Turkey, what they can show is that each rupture adds stress to another section of the fault, which then ruptures, and it just unzips as it goes along. The same thing can happen here. But there's no direct timing. It can be years before the next section goes ahead and ruptures. Anywhere between 10 and 20 years between sections on the Anatolian fault.

MKB: There's a lot of drilling for oil and gas that goes on in Oklahoma, and I've seen some speculation that this activity could be triggering earthquakes and leading to the recent increase in events. Is that possible?

AH: So, that's something I'm actively examining. The research is still in its infancy. I just started here in January. At this point, we don't see any indication that that's the case. But I'm examining it as a real possibility. The jury is still out, I'd say. Until I can prove with good science that it's the case, my assumption is that this is natural seismicity. Earthquakes have happened naturally here in the past. It doesn't have to have an outside cause.

Read more:
• United States Geological Survey: Oklahoma Earthquake Information

• Oklahoma Geological Survey: Earthquakes Page

• Center for Earthquake Research and Information at the University of Memphis: Map of recent earthquakes in the central U.S.

• CERI: 1812 New Madrid earthquake compendium—scientific reports, eyewitness accounts, newspaper articles and more


  1. She’s right about the tremors traveling a longer distance in the Midwest because of solid rock. We felt a little bit of it up here in Wichita.
    Actually, the cats and I thought it was our garage door opening when it happened, and they ran to the kitchen thinking mom had come home early.

  2. I’ve seen outcroppings of the Sandwich Fault in Illinois. Never experienced any quakes in all the time I lived there though (52-79). We were too preoccupied with tornados.

    1. #2: Don’t know where you lived in Illinois, but i can personally attest to having felt at least one temblor in 1968 while i was stationed at Great Lakes.

  3. I live in a suburb north of Dallas and yesterday morning I was sitting at my desk when I noticed it shimmy ever so slightly, just enough to make my monitor move a little bit. I thought it was odd, the kind of thing that might happen if a truck drove by, but there was nothing I could tell that caused it, so I noted the time thinking it might have been a quake. According to my PC it was 9:08am. Guess I was right about what I felt.

  4. I heard that the quake was upgraded to 5.1, thus correcting all the bugs that were found in earthquake 5.0.

  5. I was so not paying attention yesterday morning when this EQ happened.. I must have had not enough coffee.. (Location: 40 mi north of Dallas)

    Also as a side note, the range that the Arbuckle Mts in southern OK and Ozarks in AR are part of is actually part of the formation of a range that stretched from the Big Bend of Texas to the Appalacian Mts in the East..

  6. My NaNoWriMo partner/rival lives in OK and told me it felt like her cat had jumped up on her bed.

    She’s still going to clean my clock come November! ;D

  7. Central AR has been shaking like crazy past few days. The entire New Madrid system is about to completely come apart. Expect a 7.5+ magnitude quake in NM fault zone in the coming weeks or months.

  8. I know a doctor in Oklahoma who was doing brain surgery when it happened. Rattled instruments all over the operating room.

    1. doing brain surgery when it happened

      Well, now, there’s a handy excuse to void the warranty.

  9. I can’t believe our small town earthquake made it to BoingBoing! I was sitting in the Oklahoma University Library, where I work, when it hit and a few books shifted but that was it. I’m from Oakland and I just got used to earthquakes, but having one that was noticeable in Oklahoma was pretty exciting! I have friends and family who felt it almost 100 miles away from its point of origin!

  10. I live in Norman and go to school here. I was in the shower when a heard something like a loud truck go by. I had no idea anything unusual had happened until i checked facebook and saw everyone talking about earthquakes.

  11. I’m currently living in a pretty active earthquake zone. Two or three decent shakes a day for the last month. I haven’t managed to get used to it yet. My home-town was extremely lucky. 7.1 initial shake and no deaths. Pretty incredible when you compare it to Haiti (the same sized quake). Now I’m trying to figure out when to send in a claim for the damage to my house. Each shake makes the cracks a little bigger.

  12. @ anon, #11: Evidence? Please cite some peer-reviewed findings, or at least some reputable earthquake labs, before consulting your crystal ball. KTHXBYE.

  13. i don’t remember the full details of what causes them, i’m guessing they are something like the craqueleur on paintwork, which you can often see major, wider, usually much longer cracks and then in between them smaller crack patterns that usually have further sub-cracks etc etc, fractal-like. but anyway, we had one in australia in newcastle some years back, and i read an article in a magazine about it and they referred to the geographic features that signify the presence of these sub-faults as ‘killer hills’

  14. His in-laws are wise to get earthquake insurance. Tuttle creek dam, (the shadow of which i cower in, too) was for some reason built mere furlongs from a fault line. it goes, manhattan and jc are through.

  15. Hydraulic fracturing. If you don’t know what that is, look it up. Better yet, see the documentary “Gasland.” Fracking may be what’s triggering the earthquakes. It’s certainly what’s poisoning the water supply in 34 states.

  16. I live in Norman, in the second floor of a house built in the 40’s, so it’s nice and unstable. I had tied one on the night before, and had been passed out for about four hours when it hit. Woke me right up. The whole place shook. I was still drunk, and very confused. Figured it must have been a quake, since there was no sound of an explosion, rolled over and went back to sleep. Fun stuff.

  17. “somewhere between 4.3 and 4.7 on the Richter scale

    Um, no.

    As the page that link goes to notes, the 4.3 magnitude estimate uses the moment magnitude (Mw) scale; while the 4.7 estimate uses the short-period body-wave (mbLg) scale.

    Those are two different methods of estimating earthquake magnitude – and neither of them is the “Richter scale.”

    (In fact, there is no ‘Richter scale.’ The scale that Charles Richter and Beno Gutenberg developed at Caltech is actually called the Local Magnitude (Mw) scale, so named because it’s best used for estimating nearby earthquakes in California. But everybody calls it “the Richter Scale”, so we’ll live with that.)

    Reporting agencies will usually identify the scale used for the magnitude estimate in the report (usually noted as “magnitude type” or “M type”).

    The USGS generally reports moment magnitude (Mw) estimates, though they will sometimes still use Local (“Richter”) magnitudes in early reports of of small-to-moderate quakes, especially in California. (The Local Magnitude scale is inaccurate at larger magnitudes, and is specific to geological conditions in California)

    The short-period body-wave (mbLg) scale was developed to provide more refined measurements of moderate-size quakes in the Central US, and has been adapted to other regions around the world.

    All these scales are calibrated to yield very close to the same numbers within their applicable ranges; though as in this case, some discrepancies still arise.

    [Oh, and earthquakes in Oklahoma are not more likely than I think, because my estimate of the likelihood of earthquakes in Oklahoma is not what you think. :-)]

  18. These stories always make me wonder what the building code is like in the Midwest. In California, we have certain standards, but is it something that’s even thought about in the Midwest? Not that I’m suggesting the Midwest doesn’t have standards, rather standards specifically related to earthquakes.

    1. We have building codes, of course, but my understanding is that damn near nothing out here is built to earthquake-resistant standards. That’s always been the concern I’ve seen when people talk about the New Madrid fault. If we got a really big one, we’d have a lot more death and property damage because nothing is built to withstand much of anything.

      So, yeah.

    2. In fact, some building codes may even contribute to the damage – many codes in the cities of the Eastern seaboard and the Midwest are reactions to the great urban conflagrations of the 19th and early 20th century.

      Their emphasis on fireproof materials resulted in densely built urban cores featuring a great many multistory unreinforced masonry buildings. In a serious earthquake, you really don’t want to be to be in or near multistory unreinforced masonry buildings.

      There’s a reason so much of LA is built of one- and two-story buildings of lightweight timber and stucco construction. People saw the horrifying damage the 1933 Long Beach quake did to the brick buildings of Long Beach and Compton, and the unreinforced cast concrete that had recently become popular for use in schools and civic buildings.

      So, low-rise stucco it is. It contributes to LA’s sprawling and ephemeral character, and its dearth of stately architecture; but at least it doesn’t fall down and kill you in an earthquake.

  19. Yeah, Wordisbond, I see your new earthquake on the USGS map, and your earthquakes are getting bigger. What are you “guys” in Guy doin’ over there, huh? Now, don’t be gettin’ like us’ns here in California.

    I used to live in Kansas as a kid. Sure do miss it.

  20. I live in West Virginia, not known for earthquakes, and we’ve been having more lately also. The only earthquake I’ve ever felt was in the late 1970s, and I was driving across the Kanawha River on a bridge. I thought a tow-boat had run a string of barges into a bridge support, but not. 3ish on the scale, located 20 or 30 miles east of Charleston, where I was crossing the bridge.

    My wife and I think many of the recent earthquakes reported here are from mining activities, either huge blasts at mountain top removal strip mines or huge roof falls in underground long-wall mining operations. To muddy the water a bit, there’s also a lot of drilling and fracking going on in WV’s hundred-year-old oil patch, which could be lubricating faults.

    My one-time boss was driving home on the interstate in CA during the Loma Linda quake and said he saw huge waves in the concrete roadway coming toward him, and jammed on the brakes before they reached him. He decided to move back to WV that very instant, he said.

    Scary, very scary to think of a huge ‘quake in the central region of North America.

  21. Personally I think this is an ingenious marketing campaign by Blizzard for the release of their new expansion, Cataclysm.

  22. So adding this to the tennis ball sized hail, ice storm/blizzard, tornadoes, flooding…what other natural disasters is Oklahoma missing this year?

Comments are closed.