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I've been doing a bunch of videos about logarithmic scale

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and we've also -- unfortunately -- had many notable earthquakes this year

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so I thought I would do a video on the Richter Scale,

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which is a way to measure - which is a way to measure earthquake magnitudes.

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And just to be clear, although we associate the Richter Scale as the way we measure earthquakes now

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the one we actually use now is the Moment Magnitude Scale,

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and the reason why most people don't make a huge differentiation between the two is that

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the Moment Magnitude scale was calibrated to the Richter Scale

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for the whole reason why we moved to the Moment Magnitude Scale

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is that the Richter Scale starts to kind of max out at around magnitude 7 earthqukes.

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So this gives us a much better way to measure things that are above a magnitude 7.

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So this right here is a picture of Charles Richter, he's passed away,

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but this is from an interview that he gave, and it's interesting because it kinda

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gives the rationale for how he came up with the Richter Scale.

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"I found a paper by Professor K. Wadati of Japan in which he compared

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large earthquakes by plotting the maximum ground motion against the distance to the epicenter."

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So this Professor K. Wadati would -- you could imagine --

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he did a plot like this, where this is distance -- distance --

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So if you have an earthquake someplace, you aren't always sitting right on top of the epicenter

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where you measure it.

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You might be sitting over here. You're actually measure --

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your measuring stations might be some distance away.

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So he looks at how far the measuring station was and then he looks at

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the ground motion at the measuring station. So that would be some earthquake over there.

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A relatively -- let's say that's a relatively medium earthquake.

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This right over here would be a weak earthquake

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because you're close to the earthquake

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and it still didn't move the ground much. So I mean this is the magnitude,

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this axis is the magnitude.

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How much the ground is moving.

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And then for example, this would be a very strong earthquake.

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And then Charles Richter said in the interview:

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"I tried a similar procedure for our stations,

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but the range between the largest and smallest magnitudes seemed

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unmanageably large."

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So what he's saying is when he tried to plot it like Professor Wadati,

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he found that: Ok you can put -- you get some earthquakes that you can plot around here,

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but no matter how you create a linear scale, no matter how you do a linear scale over here,

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if you want any resolution down here,

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the stronger earthquakes go off the charts, or maybe off the page.

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So the stronger earthquakes you might have to start plotting here, or here,

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or maybe they don't even fit on the page.

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And so he says "Dr. Bino Gutenburg --" And they were all working at CalTech when

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they came up with the Richter Scale. "Dr. Bino Gutenburg then made the natural suggestion

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to plot the amplitudes logarithmically. I was -- I was lucky because logarithmic plots are a device of the devil."

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And I'm not really sure what he means when he says they were "a device of the devil,"

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I'm assuming he means that they're kind of magical, that all of a sudden you can take these things,

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that you want your resolution down here

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or you want to be able to tell the difference between these weak earthquakes,

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but at the same time you want to be able to compare them to the large earthquakes.

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And he thought -- I guess he viewed them as a bit of a magical instrument.

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And we say that they are logarithmic -- or he plotted them on a logarithmic scale --

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what essentially it is he's saying -- is essentially taking the logarithm of the

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magnitude of every one of those earthquakes.

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So if you're measuring the earthquake, maybe on the

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seismograph, so this is before the earthquake, then the earthquake hits,

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and then the earthquake stops and then you measure the amplitude of this earthquake.

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If you just plotted them linearly, you'd have the problem that he saw

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or if you tried to plot them the way that Professor Wadati did you'd have that problem,

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but what he did is that he measures this now and he plots the logarithm --

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the logarithm of that, and so what happens is that you get a scale that is plotted -- or that you

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get a logarithmic scale, for lack of a better word.

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But what I want to do in this video is think about what implication that has

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for the magnitude of earthquakes, especially some of the earthquakes that we have seen lately.

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So this right here is the earthquake that occured August 23rd on the East Coast of the United States

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and it wasn't that strong of an earthquake, it was a 5.8,

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that's not a small earthquake, you would definitely feel it, it's a good bit of shaking

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it could even cause some minor damage.

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But the reason why it's notable is because it happened in a part of the world

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that does not see earthquakes too frequently.

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So let's just take that on our scale. I'm going to go down way over here.

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So I'm going to do our scale over here.

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So let's just put that as a 5.8.

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I'm going to call this a 5.8.

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So if you shake your seat fairly fairly vigorously, it might help you

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know what it felt like on top of that earthquake,

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so this is 2011 East Coast Earthquake.

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And then probably the most famous earthquake in the United States is the one that occurred

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at Loma Prieta over here about 40 or 50 miles south of

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San Francisco -- and this is damage caused in San Francisco,

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a freeway collapsed right over here, and this whole area actually became very nice after they removed

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this freeway.

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But you can imagine how powerful this was, that it was able to cause this type of damage this far away

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And actually I live right over here, so I'm glad I wasn't around

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or I wasn't in the Bay Area during that earthquake.

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But that earthquake, I've -- depending on how you measure it -- is a 7.0. So that earthquake measured

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at a 7.0,

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so let's call this this over here is 7.

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Let's do that in a color you're going to see. So that earthquake

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was a 7.

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Loma Prietta. That's in the San Francisco Bay area, and that earthquake was in

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1989, it happened actually right before the World Series.

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And then in 2011 an very unfortunate

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earthquake in japan, the tohoku earthquake,

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Right over here, this circle shows the magnitude of the earthquake,

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it was off the coast of Japan

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All of these were the after shocks,

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and the damage it caused was actually the tsunami it caused

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and the damage it did to the Fukushima Nuclear Power Plant

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well sometimes it's called 8.9 or 9.0,

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let's just call that a 9.0 for simplicity.

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So this is almost 6 and this would be 7 and at 8 would get us almost over there and

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so 9.0 is right over there, so this is 2011 Japan -- the earthquake in Japan.

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And the greatest earthquake ever recorded was the Chilean earthquake in

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1960, that was a 9.5, so 9.5

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would stick us right over here.

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And this is the 1960 earthquake in Chile.

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And to just give us a sense, you know

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when you look at this, if this was a linear scale,

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you'd say that the Chilean earthquake was

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a little bit than twice as bad as the East Coast earthquake, and that doesn't seem as bad

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until you realize that it isn't a linear scale, it's a logarithmic scale

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and the way that you interpret it is thinking about how many powers of ten one of these earthquakes

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is from another.

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So you can view these as powers of 10.

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So if you take -- go from 5.8 to 7.0, that was 1.2 difference, but remember this is a logarithmic scale

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and I encourage you to watch the videos we made

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on the logarithmic scale.

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On a logarithmic scale, a fixed distance is not a fixed amount of movement

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or change on that scale

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it's not kinda a fixed linear distance,

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it's actually a scaling factor.

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And you're not scaling by 1.2 right over here.

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You're scaling by 10 to the 1.2 power.

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So this is times 10 to the 1.2 power.

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Let me get my calculator right over here and let's figure

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what that is.

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So you can imagine what it's going to be:

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10 to the first power is 10. An then you have .2.

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So it's gonna be, let's do it.

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10 to the 1.2 power. It's 15.8, so it's roughly 16 times stronger.

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So whatever shaking there was just felt on the east cost

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and maybe some of you watching this might have felt it.

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Loma Prieta earthquake was 16 times stronger.

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Let me write this: it is 16 times stronger than the one

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we've just had in the east cost.

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So that's a dramatic difference.

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Even though this caused some damage

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and this kind of shaking on, you know, on a pretty good scale

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imagine 16 times as much shaking and how much damage would that cause.

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I've actually just met a reporter who told me that

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she was in her backyard in the Loma Prieta earthquake

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not too far from where I live now

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and she says "all the cars were like jumping up and down"

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so it was a massive earthquake.

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Now let's think about the japanese earthquake.

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We could think about how much stronger was it than Loma Prieta?

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So remember: you don't just think of this as:

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"oh, it's just you know - this is just 2 times stronger".

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It's 10 to the second times stronger

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and we know how to figure that out.

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10 to the second power is a 100.

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So this right over here, so cars were jumping up and down at Loma Prieta earthquake.

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The japanese earthquake was 100 times stronger than Loma Prieta.

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And if you compare to the East Cost earthquake

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it'd be 16 00 times the East Cost earthquake that occured

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in August of 2011.

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So massive earthquake.

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And just to get a sense of how much stronger

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the chilean earthquake was at 1960...

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and there are some fascinating outcomes of the japanese earthquake.

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It was estimated that Japan over the course of earthquake

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got 13 feet wider.

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So this is doing something to the actual shape of a huge island

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and of top of that it's estimated that because of the shaking

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and the distortions in Earth caused by that shaking

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That the day on Earth got one milionth of a second shorter.

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Little over milionth of the second shorter.

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So you might say: "hey it's only milionth of a second".

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But I say, hey look! It actually changed the day of the Earth,

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the very fundamental thing and it actually matter

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when people send thing to space and probes into Mars

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that they're able to know that our day just got milionth of a second shorter.

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So this was already a massive quake

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and the chilean earthquake is going to be 10 to the 0.5 times stronger

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than that. So let's get out calculator out.

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So you can really view it as a square root of 10.

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So 10 to the 0.5 is the same thing as 10 to the one half.

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Which is the same thing as square root of 10.

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Which is 3.16.

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So the strongest earthquake on record was 3.16 times stronger

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than the japanese earthquake

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the one that shortened the day of the planet

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the one that made Japan 13 feet wider.

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And so this was, if you want to compare it to the East Cost earthquake

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this would be almost or about 5000 times stronger,

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so massive earthquake.

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So one: hopefuly that gives you a sense of what Richter scale

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is all about and also gives you sense of how massive

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some of these supermassive earthquakes are.

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And you can also appreciate what Charles Richter first problem was.

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If you want to plot all of these on the same linear plot

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you'd have to stick this one - 5000 further along an axis

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than you would have to stick this one.

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And this one itself it's still a pretty big earthquake

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so this would have to be 5000 times further than some of the earthquakes