Ways to calculate this feat for a dragon?(Magic Knight of the Old Ways)

[StorytellingDemonKing]

I don't know how to calculate anything so I'm asking here again.

Context: A dragon attacks a capital and releases a shockwave which travels several seconds, so at least 2, until it reaches the main characters. This would make the capitals size bare minimum 680m radius, I think. Now, how strong would dragon need to be to shake the ground with it's movement so that it completely knocks over people even 680m away from the center.

Is there a way to use earthquake formula or a different method to find how much strength would be needed to do this?

 

[Majinere566]

Is there like a picture or video to further understand what's going on?

 

[StorytellingDemonKing]

It is from a Light Novel so only text. I will post quotes when I get back home.

 

[StorytellingDemonKing]

Ok so I misremembered things slightly but the principle stays the same. Basically the dragon moves and with each step shakes the earth and it can be felt even 680m away.

Whether it was ordered to do so or it was simply on a whim, it was going to attack the castle directly, and it shook the earth with each step as it went.

Also this is how powerful the roar of it is described as

Almost as if to tear at the heavens, the dragon once again opened its jaws to the sky and let out an enormous roar. It was a massive wave of sound that spread throughout the capital, and after a few seconds, the powerful shock wave hit Alvin and the others head-on. The force of it blew Alvin’s body into the air and sent her rolling helplessly.

Maybe there is some more stuff I'm not remembering so I will have to read the novel again but yeah. This is about it for now.

 

[TheRustyOne]

Using the Earthquake formula

So I'll use Magnitude 5, since that is usually felt by everyone. I assume the people who felt it were outside and not in a building?

Earthquake Calculations.

For r < 60km: In this case the formula is (Magnitude at distance) + 0.0238*r = Richter Magnitude of Earthquake

Radius is 680 m or 0.68 kilometers.

So, Richter Magnitude of Earthquake= (5) + 0.0238 * 0.68 = 5.016184

Artificial quake formula: 10^(1.5*(Richter Magnitude)+4.8) = Energy in Joules

Quake power in joules: 10^(1.5*(5.016184)+4.8) = 2.10996864e12 Joules, or 504.29 Tons of TNT (Multi-City Block level)

Note: I don't know anyway that roar can be calc. But the ground shaking being felt from 680 meters away from the center is good enough for the above I think.