## 5. Locating Earthquake Epicenters

Objective:

Students will use real seismograms of recorded earthquakes to determine the locations of earthquake epicenters.

Introduction:

A simple but effective method of locating earthquake epicenters is triangulation based on the difference between the arrival times of P-waves and the arrival times of S-waves. We will use that method in this lab.

Procedure:

(1) Read the background material and perform the regional triangulation activity for locating the earthquakes in Arizona and Nevada described in the Earthquake Location: Regional Triangulation With Real Data exercises included with this curriculum (see Ortiz and Bravo, 2005; scroll down to bottom of this page for links to those exercises).

(2) Once you have mastered the technique of using triangulation to locate the earthquakes in Arizona and Nevada, apply the same method to approximate the epicenters of two earthquakes that occurred in New England. For these New England earthquakes, you will need to use the seismograms recorded by BC’s New England Seismic Network (Figures 2, 3 and 4). These seismograms correspond to two earthquakes. Figure 2 shows seismograms of an earthquake that we will refer to as “Quake 1”, and Figures 3 and 4 show seismograms of an earthquake that we will refer to as “Quake 2” (plotted with two different time scales). Your task is to estimate the epicenters of Quake 1 and Quake 2.

Reference:

Ortiz, A.M., and T.K. Bravo (2005), Earthquake Location: Regional Triangulation with Real Data, SpiNet – Science Education Solutions, Earthquake_Location_AZ.pdf and Earthquake_Location_NV.pdf

Figure 1: Stations of the New England Seismic Network, operated by Weston Observatory, Department of Geology and Geophysics, Boston College.

Figure 2: Seismograms of “Quake 1” recorded by the New England Seismic Network.

Figure 3: Seismograms of “Quake 2” recorded by the New England Seismic Network.

Figure 4: The same seismograms of “Quake 2” shown in Figure 3, but plotted on a different time scale, and including one additional seismogram.

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