Earthquakes occur in the lithosphere primarily due to the movement of tectonic plates. The lithosphere is the outermost layer of the Earth, consisting of the crust and the upper part of the mantle. This layer is broken into several large and small pieces called tectonic plates, which float on the semi-fluid asthenosphere beneath them.
As these tectonic plates move, they can interact with each other in different ways: they may slide past one another, collide, or pull apart. These interactions often lead to the buildup of stress along fault lines, which are fractures in the Earth’s crust. When the stress exceeds the strength of the rocks, it is released in the form of seismic waves, causing an earthquake.
Additionally, earthquakes can also be triggered by volcanic activity or human activities, such as mining or reservoir-induced seismicity. However, the majority of earthquakes are a result of tectonic processes in the lithosphere, making it a crucial area for understanding seismic activity.