## Overview

During one earthquake, seismic waves room sent all over the globe. Despite they may weaken v distance, seismographs space sensitive enough to quiet detect these waves. In order to identify the location of one earthquake epicenter, seismographsfrom at the very least three various places are essential for a details event. In figure 13.9, over there is an instance seismogram native a station that includes a young 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 the arrival of the S-wave. First, identify the P-wave arrival, and read down to the bottom the the seismogram to keep in mind at what time (usually significant in seconds) that the P-wave arrived. Then execute the very same for the S-wave. The come of seismic waves will be recognized by boost in amplitude – look for a pattern change as lines get taller and much more closely spaced (ex. Number 13.10).

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

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Though the distance to the epicenter deserve to be determined using a travel-time graph, the direction can not be told. A circle through a radius that the street to the quake deserve to be drawn. The earthquake developed somewhere along that circle. Triangulation is compelled to determine specifically where the happened. Three seismographs room needed. A one is drawn from each of the three different seismograph locations, whereby the radius of each circle is same to the distance from that terminal to the epicenter. The spot wherein those three circles crossing is the epicenter (Figure 13.12).