Finding Earthquake Epicenters

Yevgeniy Miretskiy and Mikhail Sabaev

Project Java Webmaster: Glenn A. Richard
Mineral Physics Institute
SUNY Stony Brook

How to Use this Applet

This applet illustrates the utilization of the arrival times of P and S waves at seismic stations to determine the location of earthquake epicenters. Since P waves travel through the shallow parts of Earth at about 8 kilometers per second, and S waves travel at about 5 kilometers per second, the P waves will arrive first at a seismic station after a quake occurs. In fact, the delay time between the arrival of the P waves and the arrival of the S waves increases with distance and can be used to compute the distance from the event.

The distance of the epicenter form each station can be repsresented by a circle of appropriate radius. With data from three or more stations, circles can be drawn on a map that intersect at the epicenter.

In this version of the Finding Earthquake Epicenters applet, you can drag the seismic stations to locations of your choice, and you can enter values for the S - P arrival time delay at each station. If the three circles intersect at a point, the location of the epicenter will be shown. If they do not meet at a point, but overlap an area, the applet will draw three chords that join the points where each pair of circles intersects. The epicenter will be shown at the point where the three chords intersect. This is one method of compensating for errors in the data. If the circles neither intersect nor overlap an area, an epicenter will not be computed. Click the Details button to see the distances computed for the data. You can change the scale of the map by entering a number in the Scale field.

Mathematical Concepts

Source List for the Three Versions of Quake

Yevgevniy Miretskiy:
Mikhail Sabaev:

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