Earthquakes in Japan

This morning, September 22nd, 2010,  around 5:30 am I was startled out of my sleep.  I wasn’t necessarily sleeping peacefully, I actually fell asleep on my living room floor by accident.  I was working on some stuff and just crashed.  But anyway, what startled me?  Was my alarm too loud?  No.  Did those Ibaraki ninjas attack me for leaving the secret organization, forcing me to use my cat-like reflexes to dispose of each and every one of them?  Ummm…No.  Did some beautiful woman break into my room and roughly try to have her way with me? Sigh…that sounds nice…but…no.  I was rumbled awake by an EARTHQUAKE!!!  It was a pretty noticeable one, too.

After a little research, I found out that the earthquake measured 5.1 on the Moment Magnitude Scale (MMGS).  What does that mean exactly?  The Moment Magnitude Scale replaced the scale that most people know about, the Richter Scale.  From what I understand the measurements are comparable, but the major difference is that the MMGS is more accurate and more useful at measuring higher quake magnitudes (don’t quote me on that, though).  The Moment Magnitude Scale’s highest measurement is 10.0 which has never been recorded.  Although 5.0 is a moderate earthquake,  the shaking is strong enough to make you take notice.

So what is an earthquake anyway?  And why does Japan have so many of them?

An earthquake is the shaking of the earth’s surface that happens as a result of the shifting of tectonic plates, sections of the earth’s crust.  Major earthquakes generally happen on or along fault lines.  If you imagine tectonic plates as giant a puzzle pieces (not interlocking puzzle pieces exactly), fault lines are where the joints of the puzzle fit together.  At these joints, tectonic plates can slide past one another creating energy.  The energy we record on the surface (seismic energy) is the transfer of that energy from the moving plates of the earth’s crust to the earth’s surface.  I’m no earthquake expert, but most likely, the reason there Japan has so many earthquakes is because the islands that compose the country, probably lie along active fault lines.

Earthquakes can definitely be one of the downsides to living in Japan.  In my hometown, Atlanta, Georgia, I’ve only felt one earthquake my entire life.  But in Japan, they are far more common.  It’s so interesting to see how most Japanese people have little or no reaction to tremors, while foreigners get that “should I panic now?” look on their faces…I’m one of the latter people.  In some cases, though, that panic can be warranted.

Many of my students mention how terrible the Kobe Earthquake of 1995 was.  This 6.8 earthquake took over 6,000 lives, the word devastating can hardly explain the aftermath.  I know what you’re thinking…6.8 isn’t that big right?  Well, although 6.8 isn’t the largest, it’s definitely getting into the high end of the MMGS.  Another thing to take into consideration is that this is a logarithmic scale.  In a nutshell, that means that going up the scale by 1 point is a 10 fold increase.  So a 6.0 is ten times more destructive than a 5.0.  The Kobe quake (which was nearly 7.0) was nearly 100 times worse than the one we had this morning.   With earthquakes, you have to consider how deep the fault lines lie beneath the city, and how close the epicenter (point of earth’s surface above the earthquake’s focus) is to a city.

When you live in Japan, earthquakes are a reality.  In the two years and seven months that I’ve been here.  I experienced at least 10 earthquakes (that’s definitely my low-end estimate), 3 or 4 of which have been a little scarier than normal. The vast majority of the quakes are no more than mild tremors, but if you’ve never experienced one before…it’s frightening. Of all natural disasters, I think earthquakes can be the most tricky because, as of now, there is no accurate method to provide sufficient, advanced warning.  As scary as  they are, truly destructive earthquakes are quite rare.  So if you’re ever an earthquake, don’t panic…follow some basic guidelines and try to stay as safe as humanly possible.

Thanks for reading,

Donald Ash

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Donald Ash is an ATLien expat who has been living in a Japanese time warp for the last six years. While in aforesaid time warp, he discovered that he absolutely loves writing, blogging, and sharing. Donald is the creator, writer, designer, editor, programmer, and occasional bad artist of blog (that's just way too many hats, dude). Wanna know more about this guy? Check out his "What's Your Story" page.
  • Kendra B.

    Actually what you’re describing here is the comparative size of amplitude of waves on a seismogram. If you want to know how much stronger one earthquake is than another the numbers are way scarier! Say you’re comparing your 5.1 earthquake to the 6.8 Kobe earthquake. The log for that is 10**(1.5*(6.8-5.1)). About 355 times stronger (more energy released.) So basically it would take about 355 of the 5.1 earthquakes to match the energy (the strength) of the 6.8 quake. When you think about how many quakes it would take to make the 9.0 from 2011 that’s huge! It would take ~1,995 6.8 quakes or 707,946 of the 5.1 quakes to match the energy released in the 2011 quake! :O

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