you can't make that assumption unless you've studied seismic waves for years and you are a professor in geology and collected data, and saw there general flow, and pattern
How the waves take different directions through different layers.
Or examined different material coming up from the earths mantle, and studying how the same waves travel through them.
Plus the simple question friend is if the earth doesn't move, what is an earth quake.
How do mountains form
Why are the tectonic plates moving.
How does condensed liquid inner mantle come out in volcanoes and outer core
why have the continents
Shifted over the years and are still moving.
What caused mount Everest to rise as big as it did.
all of this can be proven by science.