Working With the P-Wave and S-Wave Chart

Things found using the Chart

• Travel time – time a seismic wave takes to travel from epicenter to city (seismic station).

• Epicenter distance – The distance in kilometers (km) between the city and the epicenter (radius of the circle drawn on map).– When given or using the travel time for one wave

to travel the distance.– When given or using Difference in arrival time

between P & S waves (lag time).

Notice the vertical axis

This represents TIME (in minutes!)

Let’s enlarge a small section

Between each minute, we notice that there are 3 segments.

If there are 60 seconds in a minute, each one of these segments must be ________seconds.

What would this time be?

Notice the horizontal axis

This represents DISTANCE (in thousands

of Kilometers!)

Let’s enlarge a small section

There are also two curves on this chart that display the way different earthquake waves behave.

This chart can be used for answering many different questions!

How long does it take an S-Wave to travel 5,000km(travel time)?

The recording station at a city tells us it took 6 minutes and 20 seconds for the P-Wave to reach that city. How far away from the epicenter (epicenter distance) must the seismograph in this city be?

I know that there was a 7 minute difference in the arrival of my P and S waves. How far away from the epicenter must I be?

Mark off 7 minutes on scrap paper…

Slide your scrap paper up until the tick marks match up with the curves…