Question

The average density of Earth's crust $10km$ benearth the surface is $2.7gm/c{m}^3$. The speed of longitudinal seismic waves at that depth is $5.4km/s$. The bulk modulus of Earth's crustconsidering its behaviour aas 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

The correct option is A $7.9\times {10}^{10}Pa$

$\begin{array}{c}\text{Wave speed,}v=\sqrt{\frac{B}{\mu }}\\ \Rightarrow B=v^2\mu \\ \Rightarrow B=\left(2.7gm/{cm}^3\right)(5.4km/s{)}^2\\ \Rightarrow B=7.9\times {10}^{10}\text{pascal}\\ \text{Answer}A\text{.}\end{array}$