Question

The intensity of an earthquake wave passing through the Earth is measured to be 2.5×106 J/m2⋅s at a distance of 49 km from the source.

a) What was its intensity when it passed a point only 2.0 km from the source?

b) At what rate did energy pass through an area of 2.0 m2 at 2.0 km?

Answer 1

Intensity of an earthquake wave passing through the Earth is,I=2.510⁶ J/m²s

Distance from source,d₁=49 km=4910³ m

Power of source,P=I(4d₁²)=(2.510⁶4(4910³)²)=7.54310¹⁶ J/s

Part a.

Intensity when it passed a point only d₂=2.0 km=210³ m from the source is

I=P/(4d₂²)=7.54310¹⁶/(4(210³)²)=1.5010⁹  J/m²s

Part b.

Rate of energy pass through an area of 2.0 m2 at 2.0 km is=1.5010⁹(2)=3.010⁹ J/s