Lab #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 information
and perform the regional
triangulation activity for locating the earthquake in Arizona described
in the Earthquake Location: Regional
Triangulation With Real Data
exercise included with this lab (see Ortiz and Bravo, 2005).
(2) Once you have mastered the
technique of using triangulation to
locate the
earthquake in Arizona, 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
for 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,
www.scieds.com/spinet
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.
