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Q: With reference to the interior of the earth and earth quakes consider the following statements. 1. The earth's crust is brittle in nature. 2. The direction of vibrations of S–waves is parallel to the wave direction. 3. Surface waves are considered to be the most damaging waves. Which of the statements given above is/are correct ?
  • A. 1 and 2 only
  • B. 3 only
  • C. 1 only
  • D. 1 and 3 only
Correct Answer: Option D - The crust is the outermost solid part of the earth. It is brittle in nature. The thickness of the crust varies under the oceanic and continental areas. Oceanic crust is thinner as compared to the continental crust. The oceanic crust is basalt and the mean density of material in oceanic crust is 2.7 g/cm3. Secondary waves (S-waves) are shear waves that are transverse in nature i.e perpendicular to wave direction. S-waves can travel only through solids, as fluids (liquids and gases) do not support shear stresses .S wave shadow zone form the boundary of outer core as it is in liquid state. S-waves are slower than P-waves, and speeds are typically around 60% of that of P-waves in any given material hence last to report on seismograph and are considered as most damaging waves..
D. The crust is the outermost solid part of the earth. It is brittle in nature. The thickness of the crust varies under the oceanic and continental areas. Oceanic crust is thinner as compared to the continental crust. The oceanic crust is basalt and the mean density of material in oceanic crust is 2.7 g/cm3. Secondary waves (S-waves) are shear waves that are transverse in nature i.e perpendicular to wave direction. S-waves can travel only through solids, as fluids (liquids and gases) do not support shear stresses .S wave shadow zone form the boundary of outer core as it is in liquid state. S-waves are slower than P-waves, and speeds are typically around 60% of that of P-waves in any given material hence last to report on seismograph and are considered as most damaging waves..

Explanations:

The crust is the outermost solid part of the earth. It is brittle in nature. The thickness of the crust varies under the oceanic and continental areas. Oceanic crust is thinner as compared to the continental crust. The oceanic crust is basalt and the mean density of material in oceanic crust is 2.7 g/cm3. Secondary waves (S-waves) are shear waves that are transverse in nature i.e perpendicular to wave direction. S-waves can travel only through solids, as fluids (liquids and gases) do not support shear stresses .S wave shadow zone form the boundary of outer core as it is in liquid state. S-waves are slower than P-waves, and speeds are typically around 60% of that of P-waves in any given material hence last to report on seismograph and are considered as most damaging waves..