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【Illustrated and easy to understand!】Difference between seismic intensity and magnitude

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Chi-ga kun
Chi-ga kun
Hakase! I watched the earthquake news yesterday after the intensity 3 earthquake, and in the news, the words “seismic intensity” and “magnitude” were mentioned.
What is the difference between these?
Hakase
Hakase
Both of these terms come up when listening to earthquake information, but they certainly tend to be confusing.
All right, I’ m going to explain these terms in this article!

When listening to earthquake information, you are sure to hear the terms “seismic intensity” and “magnitude.”

You tend to confuse these terms, don’t you?

In this article, we will learn about these terms with the guinea pigs, along with a story about how to remember them!

Difference between seismic intensity and magnitude

Hakase
Hakase
Let me begin by explaining the difference between seismic intensity and magnitude.
Chi-ga kun
Chi-ga kun
Yes, please!
Hakase
Hakase
The seismic intensity refers to the magnitude of the tremor, and the magnitude refers to the size of the earthquake!
Chi-ga kun
Chi-ga kun
Oh, I’m pretty sure I heard a news report yesterday that said, “The magnitude of the earthquake is estimated to be…”!
Chi-ga kun
Chi-ga kun
It’s pretty much stuck in my head!
Hakase
Hakase
That’s right. Many of you may have heard the word “magnitude” used to describe the magnitude of an earthquake when listening to earthquake information.

The big difference is “whether the value varies from place to place.”

Chi-ga kun
Chi-ga kun
I still don’t quite understand the difference between seismic intensity and magnitude, what is the biggest difference between these?
Hakase
Hakase
The difference is whether the value varies from place to place.
Chi-ga kun
Chi-ga kun
What does that mean?
Hakase
Hakase
As explained earlier, seismic intensity refers to the magnitude of a tremor. The magnitude of the tremor will vary from place to place.
Chi-ga kun
Chi-ga kun
Certainly, the magnitude of the tremor will vary depending on the distance from the epicenter and the strength of the ground in that location!
Hakase
Hakase
Magnitude, on the other hand, is the size of an earthquake. In other words, it does not change from place to place, and there is only one magnitude for each earthquake.
Chi-ga kun
Chi-ga kun
If it varied from place to place, we’d have to publish a magnitude for each location!

Let’s remember with a story!

Chi-ga kun
Chi-ga kun
I feel like I understand what you have explained so far, but I think I am still not fully convinced.
Could you please explain a little more about the concept of seismic intensity and magnitude?
Hakase
Hakase
Of course. I will stay with you until you understand 100%.
By the way, do you like dogs?
Chi-ga kun
Chi-ga kun
Dogs?
I like dogs, but I’m actually a little scared of them. The other day, I was just walking outside and it barked at me so loudly that I ran for my life…
Hakase
Hakase
Perfectly appropriate!
Let’s compare the idea of seismic intensity and magnitude to a dog that barked Chi-ga kun.
How loud was the bark of the dog that barked you?
Chi-ga kun
Chi-ga kun
How loud…?
When he first barked at me, it was very loud, but as I ran away, the volume of his voice became quieter.
Hakase
Hakase
This is exactly the same as the concept of seismic intensity.
Hakase
Hakase
Both the dog barking and the intensity of the tremor vary in loudness depending on the observer’s position.
Chi-ga kun
Chi-ga kun
Sure thing!
Hakase
Hakase
In the same way, the magnitude would be the loudness of a dog barking at a Chi-ga kun.
Chi-ga kun
Chi-ga kun
The point here is that no matter where the “observer” who hears this dog barking is located, the loudness of the dog bark itself remains the same!
Hakase
Hakase
That’s right.
It’s easier to remember when you can remember things from real life experiences like this.

Summerly

Hakase
Hakase
Today, I explained the difference between epicenter and magnitude. You will always hear these terms when listening to earthquake information. Please make sure you can distinguish between them.
Chi-ga kun
Chi-ga kun
I never thought my experience of running for my life from dogs would help me understand the difference between an intensity and a magnitude! (lol)
I will review it thoroughly. Thank you for today!

Thank you for reading to the end.