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Q12 (CDS-II/2009) Science & Technology › Basic Science (Physics, Chemistry, Biology) › Waves and acoustics Answer Verified

Earthquake (shock) waves are

Result
Your answer: —  Â·  Correct: A
Explanation

Earthquake shock waves, also known as seismic waves, are mechanical waves that travel through the Earth's layers [c2]. These waves are classified as infrasonic because their frequencies are typically below the human hearing threshold of 20 Hz [t1][t3]. Specifically, seismic waves can have frequencies as low as 0.1 Hz or even 0.001 Hz [t4][t6]. While seismic waves include various types such as P-waves (longitudinal) and S-waves (transverse), they are fundamentally low-frequency oscillations resulting from tectonic movements [c5][t4]. Infrasound is defined as acoustic waves at frequencies below 20 Hz, and earthquakes are recognized as one of the most significant natural sources of such waves [t1][t4][t6]. In contrast, ultrasonic waves are above 20,000 Hz, while ultraviolet and infrared are electromagnetic waves, not mechanical shock waves [t5][t7].

Sources

  1. [1] Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 4: Earths Interior > 4.5. Seismic Waves (Earthquake Waves) > p. 59
  2. [3] Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 4: Earths Interior > Secondary Waves (S-Waves) > p. 62
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