# Linear motion of shock waves

#### trajan22

Earthquakes produce several types of shock waves. The most well-known are the P-waves (P for primary or pressure) and the S-waves (S for secondary or shear). In the earth's crust, the P-waves travel at around 6.5 km/s while the S-waves move at about 3.5 km/s. The actual speeds vary depending on the type of material they are going through. The time delay between the arrival of these two waves at a seismic recording station tells geologists how far away the earthquake occurred.

If the time delay is 33 s, how far from the seismic station did the earthquake occur?

Ive already recieved no credit for this problem but am stuck on how to get started, I just would like a small hint as to how to get started thanks?

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#### Random333

trajan22 said:
Earthquakes produce several types of shock waves. The most well-known are the P-waves (P for primary or pressure) and the S-waves (S for secondary or shear). In the earth's crust, the P-waves travel at around 6.5 km/s while the S-waves move at about 3.5 km/s. The actual speeds vary depending on the type of material they are going through. The time delay between the arrival of these two waves at a seismic recording station tells geologists how far away the earthquake occurred.

If the time delay is 33 s, how far from the seismic station did the earthquake occur?

Ive already recieved no credit for this problem but am stuck on how to get started, I just would like a small hint as to how to get started thanks?
Let the time for the P wave equal X. Therefore the time taken for the S wave equals X+33. Let the total Distance equal D

You then have two equations
3.5(X+33)=D
6.5X=D

Hopefully you can follow on from there...

#### trajan22

Yup that worked out, thanks for the help I was stuck on that for a while.

#### grantrichard2

I do not get this problem please go into more detail. Show me how to set up the equation needed to solve this problem.

I do not get how to solve his equation based on the material given in section 2.1.

Last edited:

#### ashishsinghal

what did you not understand.

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