The correct option is 1 and 3 only.
Explanation
Earthquake waves are broadly classified into two categories: Body Waves and Surface Waves. Body waves are the primary waves generated during a seismic event and travel through the Earth's interior.
- Statement 1 is Correct: Body waves are generated due to the release of energy at the focus (hypocenter). This energy release occurs when the lithospheric plates move or slip past one another, sending seismic waves through the Earth's body.
- Statement 2 is Incorrect: Body waves do not travel only in a vertical direction. They travel in all directions from the focus through the body of the Earth. They radiate spherically outward from the source, similar to sound waves in air.
- Statement 3 is Correct: As body waves travel through the Earth and reach the surface, they interact with the surface rocks. This interaction generates a new set of waves known as Surface Waves, which propagate along the Earth's surface.
Key Takeaway: Body waves originate at the focus and travel omnidirectionally through the Earth's interior, whereas Surface waves are secondary effects generated when body waves interact with surface rocks.