## Overview

During one earthquake, seismic waves space sent all over the globe. Despite they might weaken with distance, seismographs are sensitive enough to still detect this waves. In order to determine the location of an earthquake epicenter, seismographsfrom at least three different places are essential for a particular event. In number 13.9, there is an instance seismogram indigenous a station that includes a boy earthquake.

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Once three seismographs have actually been located, find the time interval in between the come of the P-wave and also the arrival of the S-wave. First, recognize the P-wave arrival, and read under to the bottom that the seismogram to note at what time (usually significant in seconds) that the P-wave arrived. Then execute the same for the S-wave. The arrival of seismic waves will certainly be recognized by boost in amplitude – look for a pattern adjust as lines gain taller and more closely spaced (ex. Figure 13.10).

By looking in ~ the time between the arrivals of the P- and also S-waves, one deserve to determine the distance to the earthquake from that station, with much longer time intervals indicating much longer distance. These ranges are established using a travel-time curve, i beg your pardon is a graph of Pand S-wave arrival times (see number 13.11).

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Though the distance to the epicenter can be figured out using a travel-time graph, the direction cannot be told. A circle through a radius that the street to the quake have the right to be drawn. The earthquake occurred somewhere along that circle. Triangulation is required to determine specifically where that happened. Three seismographs are needed. A one is drawn from each of the three different seismograph locations, where the radius of each circle is equal to the street from that terminal to the epicenter. The spot wherein those 3 circles intersect is the epicenter (Figure 13.12).