# How can a seismologist determine the epicenter of an earthquake?

Nov 16, 2009
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Earthquake Questions

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Nov 16, 2009
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Earthquake Questions

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3 comments

wil on November 16, 2009 at 6:34 pm

One way that they used to do it was by triangulation.

Imagine three seismologists with seismographs positioned at three random points detect the same earthquake. Seismologist 1 reads his meter and determines that he is, say, 30 miles from the earthquake. He will then take a map and draw on it a circle that has a radius of 30 miles around the place where he detected the earthquake. The epicenter can be anywhere along the circle’s circumference.

Seismologist 2 notices that his readings are weaker and so determines that he is, say, 80 miles from the epicenter. He takes a map and draws a circle with a radius of 80 miles from the station where he measured it.

Seismologist 3 find that he is 40 miles from the epicenter. He draws a circle around his station with a radius of 40 miles.

When the maps are overlapped, all of the circles will intersect at exactly one point. That is where the epicenter is.

Irish on November 16, 2009 at 6:34 pm

With his or her instruments.

A.Ganapathy India on November 16, 2009 at 6:34 pm

With the help of seismograph you can find arrival time of secondary wave and primary wave. The difference in time in seconds multiplied by 8 will give you the distance of focus the starting point of earthquake. Even though the speed of these waves differs according the geographical condition the difference in speed is almost constant and it is 8 k/m per second. Therefore you can draw a circle from that station .The focus point should be some where on the circumference of the circle. When you get the data from other seismic station you can draw another circle from that station that will cut the previous circle in two points .One among the two point must be the focus point. When you draw the circle in the same way from third station this will pass through one among the two meeting point of the previous circles. This point is focus.The imaginary point just above focus on earth is the epicenter. To have clear idea about this visit my slide show .I have also found a new method to find the epicenter from single station using my direction finder to gether with seismograph.It is approximate quite enough to issue Tsunami warning. I have issued the warning 2 hours before Tsunami struck our Indian coast but it was ignored. My web site . please be patient to down load .

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