The correct option is (c) 2 and 3 only.
Explanation
Earthquakes are vibrations of the Earth produced by the sudden release of energy in the Earth's lithosphere, which generates seismic waves that travel in all directions.
Statement-wise Analysis:
- Statement 1 is Incorrect: Seismic waves do not travel in straight lines. As they propagate through the Earth's interior, they encounter layers with varying densities and physical properties. This variation causes the waves to refract (bend) and reflect, resulting in curved paths rather than straight lines.
- Statement 2 is Correct: The primary cause of earthquakes is the movement of lithospheric plates. The release of energy usually occurs along a fault line where rocks slip past each other due to tectonic forces. This sudden movement generates the vibrations known as earthquakes.
- Statement 3 is Correct: The energy of seismic waves dissipates as they travel through the Earth. Consequently, the strength (intensity) of the vibration is highest at the epicentre and decreases as the distance from the epicentre increases due to geometrical spreading and attenuation.
Key Takeaway:
Seismic waves follow curved paths due to refraction caused by density variations in the Earth's interior, and their intensity diminishes with distance from the epicentre.