Locating Earthquake Epicenters

LOCATING EARTHQUAKE EPICENTERS

THE VIRTUAL EARTHQUAKE

http://www.sciencecourseware.com/VirtualEarthquake/

Read the introductory information on the page. When you have finished, double click on the box that says Execute Virtual Earthquake (bottom of page) and follow the instructions. Do Not follow instructions to go to the “new” earthquake simulation. Just go to the bottom of the page.

Follow through the exercises presented in the Virtual Earthquake. As you do so, answer the following questions:

1. Which plates and what type of plate boundary interaction do you think are responsible for earthquakes occurring in each of the regions:

a. Northern/Southern California (“Northern” California refers to San Francisco area)

b. Mexico

c. Japan

2. Which region did you choose?_____________________________

3. Define the S-P interval:

4. List the S-P interval, in seconds, for each of the 3 seismograms.

Seismogram station S-P interval (in seconds)

___________________ ________________

____________________ ________________

_____________________ ________________

5. Find the distance to the earthquake epicenter from each of the 3 seismogram stations.

Seismograph station epicentral distance (in kilometers)

___________________ ________________

____________________ ________________

_____________________ ________________

6. As the distance from the seismogram location to the earthquake epicenter increases, will the S-P interval increase or decrease? Why?

7. Explain how you can locate the epicenter of an earthquake by knowing the distance between it and 3 seismograph stations. What is this procedure called? Can it be done with information from less than 3 seismograph stations? Why or why not?

8. Continue “fine-tuning” the S-P interval and epicentral distance until you get “excellent work”. Which city on the map is closest to the epicenter of the earthquake?

9. The Richter Magnitude Scale is an indication of the energy released during an earthquake. What information on the seismogram is related to the amount of energy released?

10. In addition to your answer to #9, what other information must be known about a particular seismograph station to obtain the Richter Magnitude? Why is this other information necessary?

11. List the maximum wave amplitude, in millimeters, for each of the 3 seismograms. Remember the maximum amplitude, although always written as positive, may be actually be negative (below the x axis).

Seismograph station maximum wave amplitude (in millimeters)

___________________ ________________

____________________ ________________

_____________________ ________________

12. What was the Richter Magnitude of the earthquake you choose?

Earthquake Richter Magnitude

Note: If there is time left over, feel free to click on some of related earthquake sites.