Correct Option
The correct option is 1 only
Explanation
Earthquake waves are fundamentally classified into body waves and surface waves. Body waves are generated at the focus and travel through the Earth's interior. These are further divided into P-waves and S-waves based on their propagation characteristics and velocity.
Statement-wise Analysis
- Statement 1 is Correct: P-waves (Primary waves) travel at the highest velocity among earthquake waves. Consequently, they are the first to be recorded on a seismograph at the surface. They propagate as longitudinal waves, similar to sound waves.
- Statement 2 is Incorrect: S-waves (Secondary waves) travel slower than P-waves. They arrive at the surface with a time lag relative to P-waves. Therefore, they are recorded after P-waves on a seismogram.
- Statement 3 is Incorrect: P-waves are termed 'Primary waves' because of their initial arrival. The term 'Secondary waves' refers specifically to S-waves, which arrive second.
Key Takeaway: The sequence of arrival for earthquake waves on a seismograph is always P-waves (fastest) followed by S-waves, and finally Surface waves (slowest but most destructive).