Some Earthquake Facts and Rumors

Last Monday (September 12th) we were hit with 2 earthquakes, then this past Monday (September 19th) we had another. All of these we felt  even though the epicenter was 108 miles away from us. In the biggest one our air conditioning unit was shaking, the toilet water was sloshing around and while I was sitting on the floor I was rocked so much I almost tipped over. It was unnerving.

The big one was supposedly the largest earthquake Korea has ever experienced (they’re saying a magnitude 5.8. Maybe.) So we’ve got questions. And every time we write up informative stuff about our travels people seem to like that. So join us as we answer our own questions (and probably some of your own questions).

Remind me what those earthquake numbers mean again?

  • Great: Magnitude is greater than or equal to 8.0. A magnitude-8.0 earthquake is capable of tremendous damage. The Tohoku earthquake and tsunami that destroyed Japanese cities in 2011 was a 9. 
  • Major: Magnitude in the rage of 7.0 to 7.9. A magnitude-7.0 earthquake is a major earthquake that is capable of widespread, heavy damage. Think the earthquake in Haiti
  • Strong: Magnitude in the rage of 6.0 to 6.9. A magnitude-6.0 quake can cause severe damage. Equador was hit by one of these earlier this year. 
  • Moderate: Magnitude in the rage of 5.0 to 5.9. A magnitude-5.0 quake can cause considerable damage. This was us
  • Light: Magnitude in the rage of 4.0 to 4.9. A magnitude-4.0 quake is capable of moderate damage. This was also us
  • Minor: Magnitude in the rage of 3.0 to 3.9. Also us. 
  • Micro: Magnitude less than-3.0. Quakes between 2.5 and 3.0 are the smallest generally felt by people. Us as well. 


Some Facts:

North Korea did an underground nuclear test on September 9th which showed up as a magnitude 5.3 “earthquake” in the area (their biggest test yet).

September 12th at 7:44 an earthquake hit 11 km SSW of Gyeongju Korean sources report a 5.1 while USGS reports 4.6.

September 12th  8:33 pm an earthquake hit 8 km S of Gyeongju. Korean sources report a different location. Korean sources also  report this earthquake at 5.8 or 5.9 while the USGS reports it as a 5.4. They say this is the largest earthquake that has ever hit Korea in the history of monitoring earthquakes.

In Seoul (the complete opposite side of the country) the earthquake is felt as about a 2 or low 3.1.

22 aftershocks in the magnitude 2 range hit the Gyeongju area that night alone and I read somewhere (but can’t find the source!) that over 750 small aftershocks have hit since then.

4 nuclear reactors were shut down for the night. Trains stopped for a while in case of more aftershocks.

Monday September 19th 8:33 pm an earthquake hit 14km  (Korean sources say 11 km) SW of Gyeongju. Korean sources report 4.5 while the USGS reports it as 4.9.


So there is a map of all three of them in the lower right hand corner. We are just under the “U” of South Korea (I put a tiny white dot).

Those are all the ones we’ve felt. But there have been a lot more that people in the area (mainly the 2nd largest city of Busan/Pusan) have felt.  On September 21st there was a 3.5 which we didn’t feel. There have also been loads of earthquakes near us/near Japan since last week.

Why are Korean sources saying a different place and different numbers from USGS?

I’m not exactly sure why they have been reporting different locations and in the grand scheme of things I could care less if the epicenter was 8 km or 11 km from the city. There is a network of geological monitoring stations around the world. After an earthquake they compare notes and look at all the information again – from there it can take days to decide on a final number. The numbers the Korean sources reported on were probably from older news reports (from that night) while the USGS numbers I  were studied and decided a week after the fact. It’s not a matter of the Korean seismographs being in Korea an detecting a higher number while the USGS seismographs are in the US so they saw lower numbers. That’s really not how it works. The Korean news was just trying to put the news out quickly. I think the newer numbers are more accurate but we keep seeing “5.8” in Korean news. I think it’s just really exciting to say a large number.

 Can we expect another earthquake on September 26th at 8:33?

The craziest thing is that the earthquakes occurred exactly a week apart to the exact minute. September 12th at 8:33 and September 19th at 8:33. This has everyone all excited. And scared.

As I write this it is 7:20 pm on September 26th so if the pattern continues we’ll have another earthquake in an hour and thirteen minutes. We’ll see.

As far as anyone knows this is a crazy coincidence.

There are a lot of earthquakes in our area, is it earthquake season?

Unfortunately there is no such thing (or else it would be easy to prepare). As far as any of us know tectonic plates don’t give a hoot about weather or seasons. Recently a study came out that said earthquakes might be influenced by full moons. The first set of earthquakes were 5 days before a full moon and the most recent one was 3 days after a full moon if that means anything to anyone. But it seems to be a coincidence like everything has been so far.

Is Korea even prone to earthquakes?

3 Years ago when I looked this up the answer was basically no. Most people who blogged about living in Korea said they were super rare and never happened. There certainly had never been deadly ones. Well deadly ones in recent history.

Korea has records going back to 2AD about earthquakes. Between 2 AD and 1960s? (somewhere between the 1950s and 1970s  was when the first seismograph was installed) there were around 1,800 earthquakes. Let’s say roughly one a year. So yes, there are earthquakes here.

They have records from the 700s and 1000s about earthquakes that collapsed the-best-technology-anyone-had-at-the-time buildings. So they were deadly but probably more deadly because of the construction and safety measures of the times. And I want everyone to take a minute and appreciate the differences in our countries that Korea had kingdoms and these huge wars and was about to make a moving printer press while people in the US were just starting to get good at making jewelry. The fact that Korea even has written records of earthquakes is a big deal.


Basically no deadly earthquakes and nothing very high that we know of. If you remember that super huge horrible earthquake+tsunami in 2011 that killed so many people in Japan – that earthquake was freaking massive. So massive it moved the entirety of Japan over and shifted Korea a little bit. Korean scientists suggested Korea (the whole thing) shifted somewhere around 2.5 centimeters to the east. Seoul shifted 2.11 cm while Daejeon shifted 1.96 cm to the east. So scientists speculate that the 2011 earthquake finally put Korea in a position to start having larger earthquakes. All of this is speculation.

  • Year 2 to the 1960s(?)1,800 recorded earthquakes.
  • Missing some data….
  • 1990s – 26 earthquakes
  • 2000s -44 earthquakes
  • 2010-2014 – 58 earthquakes

The number is going up.

Korean scientists say that earthquakes happen only in places they have happened in the past. Which is why so many scientists are suggesting that all the activity in Japan – especially 2011- has shifted Korea into a situation where it’s not safe from earthquakes. So now that we’ve had a big one we will start having more and more. They say.

The only question I’m interested in is did North Korea cause those earthquakes!?

It’s easy to think this with North Korea conducting its largest ever test then 3 days later South Korea has their largest earthquake ever. Not to say coincidence for the third time but it looks like it is.

That being said no one knows as much as they would like about earthquakes. In our research we’re getting a lot of different answers to this question.

The short answer is that it didn’t cause an earthquake but maybe possibly perhaps conceivably triggered one that was going to happen anyway -earlier than it might have happened. So in a way North Korea could’ve spared the South from some major destruction if the earthquake happened in a few years but on a bigger scale.

Underground tests can trigger earthquakes, but only in the immediate area (think around 6-20 miles), and only on the same day. The North’s underground nuclear test was 310 miles away and 72 hours later.

The United States did a big underground nuclear test in 1965 in Alaska. People were super worried it would trigger earthquakes in the San Andreas Fault. It didn’t. It did cause seismic activity in the area for a while. But it didn’t trigger anything outside of the area or for a very long time. This test was a 7.0 while North Korea’s was 5.3.

Earthquakes can trigger other earthquakes. Even across 1000s of miles. They can – sometimes they do and sometimes they don’t. An already stressed fault is passed by by the sheer energy of another earthquake and it sets it off. Or when a fault ruptures and puts a bunch of stress on a nearby fault which sets it off (this seems to be what people are suggesting the 2011 earthquake did – shift that plate over a little bit into Korea’s space and now that plate is all pissed off and crowded. And ready to rupture? Or maybe it already did?) But those are real live earthquakes, the kind that shift whole plates. Not explosions.

If you want to worry about something worry about Baekdu Mountain – an active volcano on the border of North Korea and China. It’s proven an underground test of around 7.0 would absolutely trigger an eruption that would kill us all and bury everyone in the area under 4 inches of ash.

Are we in for more aftershocks? What about foreshocks?

We felt 3 earthquakes  4.5, an hour later  5.8, and a week later 4.9. So it seems it was: foreshock – main event – then aftershock. But you can’t really label anything until everything is finished. And we might not be finished. After that massive 2011 earthquake Japan had 9,500 aftershocks (as of 2013, I don’t have any data after that).

So it could be that we will have little earthquakes all the time. We could have big ones all the time. We could have a super huge one that rips apart cities in southern Korea.

A professor of geology said “Aftershocks sometimes last for more than a year. The worst quake that took place in Gyeongju shook fault lines and we don’t know how surrounding fault lines will move around … We don’t know whether the latest quake was an aftershock or a precursor to bigger quakes in the years to come.”

Can all those little earthquakes prevent a big one?

No. A cool fact is it would take 42 million earthquakes at magnitude 2 to release the same energy as a magnitude 7. So the 700 some-odd eeinsy weensy ones haven’t even scratched the surface.

The juiciest rumor yet: did South Korea conduct underground nuclear tests in retaliation/practice or as a show of force against the North’s recent test?

No questions are stupid questions. So let’s address this.

The way this rumor goes is this – the current president Park GuenHee’s dad was the president/dictator of South Korea in the 1960s. He had a little nuclear program of his own for a while. Gyeongju (where the earthquakes have struck) is the center for Korean nuclear power and nuclear…stuff. So people think it was Park Junior showing off daddy’s power or using family legacy to mess around with nuclear…stuff. So this conspiracy theory certainly is juicy with family drama, legacy, birthright, and nuclear tests.

But stupid.

First of all the dictator’s nuclear dabbling was shutdown by the US. So there isn’t even nuclear stuff to play with. If you want to go tin-foil hat and say there is stuff the south has stockpiled then lets look at some real facts. The earthquakes were really really deep. The USGS says about 10km deep. The world’s deepest mine is not quite 4 km. So unless the South has some really deep secrets (literally and figuratively) nope. Also explosions and earthquakes appear on seismographs differently. So everyone at a geological survey station who looks at the charts would know immediately if its an explosion or earthquake. Unless you rumor gets really juicy with the US and South Korea working together to dig massively deep mines, report earthquakes falsely and then silence any poor geologist who speaks up. Nope. Nope. Nope.

How’s Korea handling their largest earthquake to date?

I’ll leave a quote here:

“It is so shocking that there has been no changes to government safety protocols even though we went through MERS and the Sewol crisis,” said Rep. Won Hae-young of The Minjoo Party of the Korea.

It’s a political mess. Finger pointing galore.

No one is doing anything. We haven’t had any drills or talked about it in schools. My coteachers are still under the impression the best thing to do is put a book over their heads and run outside (good luck).

Something like 4,000 people called the fire departments when it happened. People as far away as Seoul called emergency numbers to report… what? Exactly?

The actual people of Gweongju (where it happened) had a lot of structural damage to walls, a few people were injured mostly by TVs falling. Lots of broken glass and damaged groceries. But no one died.

Pictures were posted of people playing on phones in the middle of elementary school fields. That’s basically the safety plan.

We have a problem with everyone thinking you have to run outside immediately. Like while the world is a shakin’ you make a run for the field. That’s a great way to get pitched headfirst down some stairs or have some ceiling tiles fall on you.

If you learn something new today learn this – the Triangle of Life is a lie, ignore that doorframe crap. Just get under a desk and hold on and stay there. When it seems safe to go then go. But don’t try to calculate a triangle of safety beside a desk when you could just go under a desk. Don’t stand in a doorway when you may just fall over anyway. If you’re in bed stay in bed. The end. You just learned what to do.

What’s sad is that the teachers haven’t been trained, thus the students are at the mercy of idiotic adults who will tell them the wrong thing (like how when the ferry sunk the adults said to stay in the cabins where all the students then drowned).

One person quoted saying “For me, I have no idea about what to do when the quake strikes. The government should prepare measures to promptly inform the public of how to respond in emergency cases” You can see the confusion with people calling 119 (you can guess what that number is) to ask what to do. No one is prepared.

Our earthquake drills at school (we’ve had one this year and it was back in April) have involved going to the gym and sitting in lines based on class. This is so stupid. All those heavy gym lights that could fall on everyone? The worst part is our doors are chained shut with a huge chain. No one could even evacuate if they wanted to. A fire, an earthquake? Someone with a gun or knife? We aren’t going anywhere. It’s just going to take a Columbine or earthquake of massive destruction before anything will be changed for school safety.

Korea’s mad at the government but quietly slipping into complacency and apathy. The more time that passes since the earthquake the less people are worried. The less they want emergency systems or plans. There are all these stupid rumors about how people knew the earthquake was going to happen because of a smell in the city. A smell?!

In short: no one is educated. We’re all operating on rumors. No one will push for education or better measures. No one wants to be educated, we all want to think about these funny ideas about the North or the South.

At the same time there isn’t even enough education. On the grand scheme of things scientists don’t really know that much about earthquakes.

Fortunately the risk is fairly low where we are and we can only hope that no more earthquakes, or anything, happen in this innocent little peninsula.



We think most brands of soju taste more or less the same so we tried a bunch of different kinds and filmed ourselves. Maybe this video isn’t so good but we had a lot of fun producing it and getting creative with it. If you’re interested here it is:

Here’s the link: Trying Soju