[ETL]

As you said, the water movement also causes movement of the ground below it.

That was only a guess. I don't know for sure. I do know that water places a significant role in plate tectonics, both at the spreading centers, and even more so, at the subduction zones, where one plate is diving beneath another. Lots of seawater goes down with the subducting plate and acts as a catalyst for lowering the melting point of the rock as it reaches the hot mantle. This results in explosive volcanic activity along the margins of colliding plates.

[UCANSEE2]

That was only a guess.

But a logical one.

I don't know for sure.

No one does. That is why earthquakes, volcanoes, and weather are so unpredictable. TOO MANY FACTORS to evaluate properly. Some of the factors are not well understood.