What is seismic focus. Where is it situated?

Explanation

**Step-by-Step Solution:**

1. **Definition of Seismic Focus:**
- The seismic focus, also known as the hypocenter, is the point within the Earth where an earthquake originates. It is the location where the seismic waves are generated.

2. **Understanding Seismic Waves:**
- When an earthquake occurs, it causes the tectonic plates to shift. This movement creates seismic waves, which are the energy waves that travel through the Earth and are felt as shaking during an earthquake.

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