Question

What types of waves are produced before an earthquake?

• A. Audible
• B. Ultrasonic
• C. Infrasonic
• D. None of these.

Answer 1

The correct option is C

Infrasonic

1. Earthquake is defined as a movement of plates of the earth, below its surface which is the earth's crust.
2. It generally originates naturally and below the earth's surface.
3. An earthquake generates an infrasonic sound, generally before the mainshock.
4. This sound is inaudible to human beings.
5. Infrasonic sound is a very low-frequency sound whose frequency is always less than $20Hz$.

Hence, option C is correct.