Question

The average density of Earth's crust $10\, km$ beneath the surface is $2.7\, gm / cm ^{3}$. The speed of longitudinal seismic waves at that depth is $5.4 \,km / s$. The bulk modulus of Earth's crust considering its behaviour as fluid at that depth, is

• A. $7.9 \times 10^{10} Pa$
• B. $5.6 \times 10^{10} Pa$
• C. $7.9 \times 10^{7} Pa$
• D. $1.46 \times 10^{7} Pa$

Answer 1

Answer: (A)

$ v=\sqrt{\frac{B}{\rho}} $
$\Rightarrow B =v^{2} \rho=\left(5.40 \times 10^{3} m / s \right)^{2}\left(2.7 \times 10^{3}\right)$
$=7.6 \times 10^{10} Pa$