## Your task will be to locate the epicenter for the earthquake using the arrival time of P-waves and S-waves from several seismic stations.

### science

##### Description

Introduction:

Your task will be to locate the epicenter for the earthquake using the arrival time of P-waves and S-waves from several seismic stations. Upon completion of the virtual lab, you will write a laboratory report of your results.

Problem:

How can we use seismic waves to determine the epicenter of an earthquake? Seismologists use data from seismographs to locate an earthquakes epicenter.

Hypothesis:

Review the Introduction tab of the pre-lab within the lesson. Hypothesize how seismographs will be used to pinpoint the epicenter of the Earthquake.

To establish the pinpoint of the epicenter of an earthquake seismologist use a method called triangulation.

Materials:

Use the reference image in the Reading Seismographs tab of the pre-lab to identify the S-P Time interval of a seismograph reading. Use the Determining Distance to an Epicenter tab and the Locating an Epicenter tab of the pre-lab as practice before completing the procedures below.

#### Procedures:

1. Examine the reference image under Materials to learn to identify the S-P time interval of a seismograph reading.
2. Under Data and Observations, determine the S-P time intervals of all three stations using the time scale under the seismograph readings. For example, if P wave arrives at 2:02 pm and the S wave arrives at 2:27 pm, the total S-P time interval is 25 minutes.
3. Record the time interval for each station in Table 1 under Data and Observations.
4. To determine the distance from each seismograph to the epicenter, you multiply the S-P time interval by 10. For example, if the time interval is 25 minutes, 25 x 10 = 250 kilometers.
5. Record the calculated distance to each station from the epicenter in Table 1 under Data and Observations.
6. Next, use the distance scale under Data and Observations to measure the three circles provided, each with a radius that equals the distance of each station. To measure, place the center of each circle at zero. An example measurement is shown below for a 75 km radius.