# 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?
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.
```