  We propose a novel method for testing gravity models using seismic data from
Earth. By imposing observational constraints on Earth's moment of inertia and
mass, we rigorously limit the gravitational models' parameters within a
$2\sigma$ accuracy. Our method constrains the parameters governing additional
terms to the General Relativity Lagrangian to the following ranges:
$-2\times10^9\lesssim\beta\lesssim 10^9 \text{m}^2$ for Palatini $f(R)$
gravity, $-8\times10^9\lesssim\epsilon\lesssim 4\times 10^9 \text{m}^2$ for
Eddington-inspired Born-Infeld gravity, and
$-10^{-3}\lesssim\Upsilon\lesssim10^{-3}$ for Degenerate Higher-Order
Scalar-Tensor theories. We also discuss potential avenues to enhance the
proposed method, aiming to impose even tighter constraints on gravity models.
