This activity was developed by Anne Ortiz and Tammy Baldwin and is offered through Science Education Solutions. Many Earth science textbooks contain a description of earthquake location by triangulation from three seismic stations. Distance of the earthquake from each seismic station is determined using the time difference between the arrivals of the primary (P) and secondary (S) waves from the earthquake. This activity permits students to use real seismograms to determine the arrival times for P and S waves and use these times to determine the distance of the seismic station from the earthquake. Seismograms from four seismic stations are provided, although only three records are required to determine the epicenter using the S-P method. Because real seismograms contain some "noise" with resultant uncertainty in locating arrival times of P and S waves, this activity promotes appreciation for uncertainties in interpretation of real scientific data. Note that Science Education Solutions holds the copyright but allows educational use of this activity.

An additional regional triangulation activity is available through Science Education Solutions at http://www.scieds.com/spinet/pdf/triangulation.pdf