Earthquake is caused by a disturbance deep in side the earth's _____

Explanation

**Step-by-Step Solution:**

1. **Understanding the Earth’s Structure**: The Earth is composed of several layers, including the inner core, outer core, mantle, and crust. The crust is the outermost layer where we live.

2. **Identifying the Cause of Earthquakes**: Earthquakes are caused by disturbances that occur deep within the Earth. These disturbances are primarily related to the movement of tectonic plates.

3. **Tectonic Plates**: The Earth's crust is divided into several large pieces known as tectonic plates. These plates float on the semi-fluid mantle beneath them.

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