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Location of an epicentre - 2
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On the previous page we discovered how to calculate the distance of the siesmology station from the epicentre of an earthquake, using the difference in arrival time between P and S waves.

Now we are going to locate the position of the epicentre of this eathquake. To do this we need seismometer traces of this same earthquake from two other stations.

Have a go imageThe circle of possible epicentre locations from Phnom Penh, previously calculated, is already drawn for you.

  1. Consider a second seismograph reading, this time from a station at Puerto Princes.
  2. Calculate the distance of the epicentre from Puerto Princes, dPP.
  3. Click and drag the mouse from Puerto Princes across the map until the radius of the circle is approximately your measured value of dPP. Click to use calculator

Questions imageThe two circles should intersect at two points. These give two possible locations for the epicentre. What are they?

Rangoon and Hanoi     Singapore and Rangoon    Hanoi and Singapore

Have a go imageA third seismograph reading is needed to pinpoint which of these two locations it is.

  1. Consider a reading from a station at Kuala Lumpar.
  2. Calculate the distance of the epicentre from Kuala Lumpar, dKL.
  3. Click and drag the mouse from Kuala Lumpar across the map until the radius of the circle is approximately your measured value of dKL.

Questions image Where all three circles intersect identifies the location of the epicentre. Where was the epicentre located?

Hanoi     Singapore

You have now completed this exercise.  Before you quit the package, return to the title page and check that the learning outcomes have been achieved.

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