If you want to really nerd out see
https://www.physicsforums.com/threads/weight-of-objects-as-they-descend-into-the-earth.207148/
Essentially gravitational field becomes stronger in many places just below the earths crust. This being due to the crust being less dense enough to keep us a bit distance away from the really dense part of the planet. Fluffy crust? From there, the maximum, the field is thought to go approximately linearly to zero at the center.