The intensity of an earthquake wave pasing through the earth is measured to be 3

ID: 1660631 • Letter: T

Question

The intensity of an earthquake wave pasing through the earth is measured to be 3000000 w/m^2 at a distance of 54 km from the source.

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Modify Equation 11-16a or I = power/area for a HEMISPHERICAL wave, as this earthquake

approximately is. That is, assume it spreads out over the area of a HALF sphere.

A) Use this (and the fact that 54.0km is 5.40E4m) to find the power (watts or J/s) of this

earthquake. I got between 5E16 watts and 6E16 watts.

B) Find the intensity 10.0km from the source

Remember, intensity is

power/area.

C) Finally, find the power through the area of a square 5.00m on a side.

A) Power P = IA

= 3000000 * 4piR2

= 3000000* 2pi * (5.40E4)2

= 5.5 x 1016 W

B) Here R = 10km = 10,000m

I = P/A

= (5.5 x 1017)/2pi*10,0002

= 8.75 x 107 W/m2

C) P = IA

A = side2 = 52 = 25m2

I is not mentioned. Assuming it to be as given in the original question:

I = 3000000 w/m^2

P = 3000000 w/m^2 *25m2

= 7.5 x 107 W

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