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# Activity Instructions > Seismology: "S minus P" Earthquake Location Method

**Allison Mote, TXESS Revolution teacher, works on the graphing part**

of the activity during PDA3a in 2009.

of the activity during PDA3a in 2009.

*(Photo courtesy H.C.Olson)*

**Teaching Strategy: Guided Inquiry**

This activity models (1) S and P wave propagation and (2) a technique used by seismologists to locate earthquakes. This technique is called the S and P Wave Travel Time Simulation (or “S minus P” Earthquake Location Method). We will use an approach that the developers, L .and S. Braile, have named the **Walk – Run** method. In this method S wave propagation is simulated by *walking* and P wave propagation is simulated by *running*. The Walk – Run method requires an “open space” of about 30 x 30 meters—a playfield or a gymnasium.

The purpose of this activity is to model the different speeds of P and S waves as they travel from the epicenter of an earthquake. The procedure is in three parts.

** Part One:** Simulating an earthquake with students acting as P waves (runners) and S waves (walkers). Part one gives students an idea of how activity will unfold.

** Part Two:** Constructing the Travel-Time Graph

** Part Three:** Locating an Earthquake using S minus P (Run – Walk) times and Triangulation