The outermost layer of the Earth where earthquakes occur is the lithosphere.

Here's why:

* Lithosphere: This is the rigid, outermost layer of the Earth, composed of the crust and the uppermost part of the mantle. It's broken into tectonic plates that constantly move and interact with each other.

* Earthquakes: Earthquakes are caused by the sudden release of energy in the Earth's crust, typically along fault lines where tectonic plates meet.

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