Earthquake Waves: Calculate Distance from Station

In summary, the conversation discusses the different types of shock waves produced by earthquakes, including P-waves and S-waves. The time delay between the arrival of these waves at a seismic recording station can be used to determine the distance of the earthquake from the station. The given problem involves finding the distance of the earthquake from the station using the known velocities and time delay.
  • #1
maff is tuff
65
1

Homework Statement



Earthquakes produce several types of shock waves. The best known are the P-waves (P for primary or pressure) and the S-waves (S for secondary or shear). In the Earth's crust, P-waves travel at around 6.40 km/s while S-waves move at about 3.60 km/s. (The actual speeds vary with the type of material the waves are going through.) The time delay between the arrival of these two types of waves at a seismic recording station tells geologists how far away the earthquake that produced the waves occurred.

If the time delay at a seismic station is 41.0 s, how far from that station did the earthquake occur?


Homework Equations





The Attempt at a Solution



This one is really stumping me. Maybe I am missing something big. My givens are: I know two different velocities (6.4 km/h and 3.6km/h) and I know a time delay of 41 seconds. So that means that the first wave gets there 41 seconds before the second wave does. I don't really know what to do with this information. The only thing I could think of is using the formula: v^2 = v0^2 + 2a(x-x0) but since I don't know "a" I could maybe plug in (v-v0)t for "a"? I really don't know where to start. Only thing I can think of that I know I'll eventually have to do is convert 41s into .01139 hours. Can I come of with an acceleration by taking the difference of the velocities and dividing by the .01139h? Can anybody get me started? Thanks!
 
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  • #2
The problem gives the velocities in km/s, and the time is in seconds, no need to convert the velocities to km/h.
The velocities are constant, there is no acceleration.

Forget about earthquakes, try to think of this more familiar problem: You and your sister start from home and go to the school. You walk with 6.4 km/h and your sister walks with 3.6 km/h. You arrive a quarter of hour earlier than your sister. How far is the school from your home?

ehild
 
  • #3
Ok thanks I don't know why I converted it. Yeah thanks for the explanation; it helped.
 

1. How do earthquake waves travel?

Earthquake waves travel through the Earth's interior in all directions from the focus, which is the point where the earthquake originates. These waves can be classified into two types: body waves and surface waves. Body waves travel through the interior of the Earth, while surface waves travel along the surface.

2. What is the difference between P-waves and S-waves?

P-waves, or primary waves, are the fastest type of earthquake waves and are the first to arrive at a seismic station. They can travel through solid, liquid, and gas. S-waves, or secondary waves, are slower than P-waves and can only travel through solid materials. They arrive at the seismic station after P-waves.

3. How are earthquake waves used to calculate distance from a station?

Scientists use the time difference between the arrival of P-waves and S-waves at a seismic station to determine the distance from the station to the earthquake's epicenter. The longer the time difference, the farther the distance from the station to the epicenter.

4. What is the formula for calculating distance using earthquake waves?

The formula for calculating distance from a station using earthquake waves is: Distance (in kilometers) = (Time difference between P-waves and S-waves) / (P-wave velocity - S-wave velocity). The average velocity of P-waves is about 8 kilometers per second, and the average velocity of S-waves is about 4.5 kilometers per second.

5. Can distance be accurately calculated with only one seismic station?

No, distance cannot be accurately calculated with only one seismic station. At least three seismic stations are needed to determine the distance to the epicenter of an earthquake. This is because the time difference between P-waves and S-waves can vary depending on the location of the stations in relation to the earthquake's epicenter.

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