P and S waves generated by the World Series Earthquake traveled away from the epicenter and were recorded at the three locations on the map below.

  !   Click each city on the map to see the seismogram and travel-time graph for that location. Interpret the graph to find the distance from the recording station to the epicenter, and answer number 1 below. If necessary, review the Interpreting a Travel-Time Graph section on page 218 of your textbook.

1. What do you notice about the time interval between the arrival of P and S waves at the three different seismograph stations? What causes these differences?

Using the known distance to the epicenter from three different locations, circles with radii of the indicated distance are drawn around each of the recording cities. The place where the three circles intersect is the epicenter location.

  !   Click the buttons for each city below the graphic to show a circle indicating the distance to the epicenter. The intersection of the three circles is the epicenter location.

The three circles intersect near the city of Loma Prieta, California, so Loma Prieta was the epicenter of the earthquake. Thus, the World Series earthquake is also known as the Loma Prieta earthquake.