Question

An earthquake produces which kind of sound before the main shock wave begins.

• A. Ultrasound
• B. Infrasound
• C. Audible sound
• D. None of the above

Answer 1

The correct option is B

Infrasound

The explanation for the Correct option:

In the case of option B:

1. Infrasound is sound waves with a frequency lower than 20Hz.
2. An earthquake is a sudden movement of the earth's tectonic plates that creates tremors in the crust.
3. It generates infrasound waves before the main shock wave arrives.
4. During this process, seismic waves are released suddenly, causing the ground to tremble. These seismic waves are classified as infrasound waves.
5. This infrared sound, also known as low-frequency sound, refers to sound waves with frequencies below the lower limit of audible frequency, which is generally considered to be twenty hertz. Because the frequency is so low, hearing these infrared frequencies is not possible or perceivable.
6. Few animals can hear this infrasound because of this these animals start acting weird before an earthquake.

The explanation for the incorrect option:

In the case of option A:

1. Ultrasounds are sound waves with a frequency higher than 20000Hz.
2. These are high-frequency waves, these waves are out of the audible range of humans.
3. Some animals or birds such as bats use these waves to hunt at night.

In the case of option C:

1. Audible sounds are sounds that can be heard by humans.
2. The frequency of audible sound waves is 20Hz to 20000Hz.
3. We are not able to hear the sound waves produced before the earthquake, hence these sound waves can't be audible sound.
4. Hence option C is incorrect.

In the case of option D:

1. The sound produced before the earthquake is infrasound, which is option B.
2. Hence option D is incorrect.

Hence, option B is correct.