How do geologists use earthquakes to obtain information about Earth's interior?

Question

How do geologists use earthquakes to obtain information about Earth's interior?

Answer 1

You will get far better answers if you ask your question in Earth Science-Geology category instead of the Astronomy category.

Answer 2

I'm only 14,so don't expect any smart words,but let me put it this way,imagine the Earth as a pregnant woman's belly,the sound waves travel through her stomach until they meet the baby.Once that happens,the sound waves go back from the point where it met the baby,to the surface(or machine,not sure),creating a 3D image of the baby.Same thing with the Earth,but because it has many layers,the sound waves change in frequency,going faster or slower during each change in layers.Then they bounce back and the machine picks up the small changes and converts them into a 3D image.