To clarify, gravitational waves are not directly caused by the expansion or contraction of the Earth's surface. Gravitational waves are ripples in the fabric of spacetime that are generated by accelerating massive objects. They are produced by cataclysmic events such as the collision of black holes or the explosion of supernovae. These events involve a significant amount of mass and energy in motion, causing disturbances in spacetime that propagate as gravitational waves.
The expansion and contraction of the Earth's surface, on the other hand, do not generate gravitational waves in the same way. While various geological processes like earthquakes and volcanic activity can cause vibrations and seismic waves, these are different from gravitational waves.
Gravitational waves require extreme masses and accelerations to be generated. The expansion or contraction of the Earth's surface, even on a global scale, would not be sufficient to generate gravitational waves significant enough to be detectable. Gravitational wave observatories, such as LIGO and Virgo, are designed to detect incredibly tiny disturbances in spacetime caused by massive astronomical events occurring in distant parts of the universe.
Therefore, it is not possible to determine a specific distance by which the Earth's surface would need to expand or contract to cause gravitational waves, as the two phenomena are fundamentally different in nature.