# How would giant creatures that "live" underground shifting their limbs affect seismic activity

Please excuse me if I make any mistakes, this is my first post here.

If there were giant creatures, ranging anywhere from 20,000 square miles (approx. 30,100 square km) to 100,000 square miles (approx. 160,000 square km) large, that were dormant dozens of miles/km underground and they occasionally shifted an extremity akin to a finger or toe, how would that shifting impact the land above them? Would it cause earthquakes? Or have a different effect? No effect?

I'm just toying with this idea and have no background in geology, so I really don't have a clue how this would work realistically. Even somewhat vague answers would be much appreciated.

• What's the shape of this beast ? Is it snake-like, whale-shape, or flat and wide.. or tree-like... and how does it behave since it woke up.. Jan 18, 2023 at 13:45

You've not given us a lot of detail, so...

• Let's assume the creature looks suspiciously like a human.

• Based on your numbers, an average creature size is 60,000 square miles.

• After some nasty algebra (1/7=x/y and x*y=60,000 solve first for x), that means your creature is more or less 93 miles wide and 648 miles long.

• Roughly, hand length vs height is 1:8.9 so the creature's hand is 73 miles long... so a finger is roughly 36 miles long.

Would shifting a 36 mile long object that's a couple of dozen miles underground cause tremors? Yup, I could believe that. But it would depend on how much the shift is. A bare wiggle wouldn't impress your average Los Angelenos, but move that finger a couple of miles (about 5% of the finger's length) and, yeah, I think even the Angelenos would be impressed.

• Sorry about the lack of details, still have to work out what these things might look like. Your answer was very helpful so thank you! Jan 18, 2023 at 5:21