Question

An earthquake generally produces which type of sound wave before the main shock wave begins?

• A. Ultrasonic
• B. Supersonic
• C. Infrasonic
• D. Audible sound

Answer 1

The correct option is C Infrasonic

Seismic waves are waves of energy that travel through the Earth's layers and are a result of earthquakes, volcanic eruptions, magma movement, large landslides and large man-made explosions that give out low-frequency acoustic energy. The frequency of seismic waves can range from about ${10}^{-3}Hz$ to $50Hz$.
Infrasonic waves are category of waves with frequencies less than 20 Hz. Almost all the seismic waves are infrasonic waves.