Determining the Epicenter of an Earthquake

Complete this activity following the Earthquake and Volcano activity. 

How fast do p and s earthquake waves move?  Use the Earthquake1 simulation. Open ExploreLearning. com.

An earthquake releases an enormous amount of energy, which passes through Earth’s interior in the form of body waves. There are two types of body waves: P-waves (primary waves) and S-waves (secondary waves). 

Scientists study earthquakes with the aid of an instrument called a seismograph. When seismic waves reach the seismograph, a graphical record, or seismogram, is produced.

Place the recording station at five different distances to the epicenter. Measure the P- and S-wave time difference (∆t) on the seismogram at each distance, and record the values in this spreadsheet.  

You can now see a graph of the time differential between the arrival of the p and s-waves as a function of the distance from the epicenter by examining this graph.  All teams can use this graph to determine the distance a seismograph is from an epicenter. 

Determine the epicenter of an earthquake.  Use the Earthquake 2 simulation

Turn on Show time probe. On each seismogram, locate the arrival of the P-wave and the arrival of the S-wave. Measure the time interval (∆t) for each seismographic station, and then use the graph you just made to find the distance of each station to the epicenter.  Draw a radius for each station equal to the distance from the epicenter.  The epicenter is where all three circles intercept.