Description

Geologic Events Lab Report

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?

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.

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. 

7. Place each of the measured circles around the station on the map that they represent. All three circles should have one intersecting point that matches the epicenter.
8. Complete the Questions and Conclusion section of the lab report.

Variables:

For this investigation, list the independent, dependent, and controlled variables.

Data and Observations:

S-P Time Intervals