Consider the following statements :

I. In a seismograph, P waves are recorded earlier than S waves.

II. In P waves, the individual particles vibrate to and fro in the direction of wave propagation whereas in S waves, the particles vibrate up and down at right angles to the direction of wave propagation.

Which of the statements given above is/are correct?

Both statements are correct. P-waves (Primary waves) are the fastest seismic waves and are the first to be recorded by a seismograph. They are longitudinal (compressional) waves, meaning the particles of the medium vibrate back and forth (to and fro) in the same direction that the wave travels.

S-waves (Secondary waves) travel more slowly than P-waves and arrive at the recording station later. They are transverse (shear) waves, where the particles of the medium vibrate at right angles (perpendicularly) to the direction of wave propagation. This fundamental difference in speed and particle motion is used by seismologists to locate the epicenter of earthquakes and study the Earth's internal composition.