# Virtual Earthquake Lab 10 24 13

```Virtual Earthquake Lab
Name:_______________________________________________
Go to: http://www.sciencecourseware.com/virtualearthquake/VQuakeExecute.html?x=75&amp;y=39
1. Earthquakes occur because of a sudden release of stored _____________________.
2. This sudden motion causes shock waves (_____________________) to radiate from their point of
origin called the _______________ and travel through the earth.
3. Each year there are ____________________ of earthquakes that can be felt by people and over
__________________________ that are strong enough to be recorded by instruments.
4. Weaker seismic waves can travel far and can be detected by sensitive scientific instruments called
________________________.
5. We are interested in only two types: P (______________) waves, which are similar to sound waves,
and S (_______________________) waves, which are a kind of shear wave.
6. Within the earth, P waves can travel through _________________ and _______________, whereas S
waves can only travel through ___________________.
7. Speed changes mostly with ____________ and ______________ type.
8. In order to locate the epicenter of an earthquake you will need to examine its seismograms as
recorded by _____________ different seismic stations.
9. On each of these seismograms you will have to measure the S - P time ________________ (in
seconds). (In the figure, the S - P interval is about ______ seconds.
10. The actual location of the earthquake's epicenter will be on the ________________ of a circle
drawn around the recording station.
11. Three stations are needed in order to &quot;_____________________&quot; the location.
**Choose a region from the list and click “submit choice”
12. You have to measure the interval to the closest second and then use a graph to convert the S-P interval to
the _______________________ distance.
**Click “view seismograms”
Use the three seismograms to estimate the S-P time interval for each of the recording stations. Record
your measurement for the S-P interval in the box below each seismogram.
13. S-P Interval =
seconds
14. S-P Interval =
seconds
15. S-P Interval =
seconds
**Click “Convert S-P Interval”
16. Examine the graph to the right, a graph of seismic wave travel times. There are three curves on the
graph: The upper curve shows ____________ travel-time graphed versus distance, the center one shows
P wave travel time versus _____________, and the lower one shows the variation in distance with the
___________________ of the S and P travel times.
17. It takes an S wave approximately _____________ seconds to travel __________ kilometers.
**Use the S-P graph to the left and the estimates you made for the S-P time intervals for the three
seismograms (shown again for your convenience) to complete the table below.
Station
**Click “Find Epicenter”
S-P Interval
Epicentral Distance
_______sec
KM
_______sec
KM
_______sec
KM
18. Triangulation of the Epicenter (write the line following this heading): _________________
**Click “view true epicenter” (or click “remeasure” if you’d like to give it another shot)
Complete the table below with the “ACTUAL DATA” numbers that should have gotten:
Actual Data
Recording Station S-P Interval Epicentral Distance
_____sec
_____ km
_____sec
_____ km
_____sec
_____ km
19. The location of the epicenter determined from your measurements of S-P intervals &quot;should&quot; be at
the point ______________ of the three epicentral circles.
20. Among other factors, ________________ in rock types through which the waves travel will change
the actual travel times and hence the S-P intervals.
**Click “Compute Richter Magnitude”
21. A well-known scale used to compare the strengths of earthquakes involves using the records (the
____________________) of an earthquake's shock waves.
22. The scale, known as the ____________________________, was introduced into the science of
seismology in 1935 by Dr. C. F. Richter of the California Institute of Technology in Pasadena.
23. The ____________________ of an earthquake is an estimate of the total amount of energy released
during fault rupture.
24. The Richter magnitude of an earthquake is a number: about _______ for earthquakes that are strong
enough for people to feel and about _______ for the Earth's strongest earthquakes.
25. The most sensitive seismographs can record nearby earthquakes with magnitude of about ______
which is the equivalent of stamping your foot on the floor.
26. Two measurements are needed: the __________________________________ and the
_________________________________ of seismic waves.
27. The blue horizontal grid lines are spaced at _________ millimeter intervals. In this example the
maximum amplitude is about ____________ mm.
**Click “Go to next page”
28. Although the relationship between Richter magnitude and the measured amplitude and S-P interval
is complex, a graphical device (a ____________________) can be used to simplify the process and to
estimate magnitude from distance and amplitude.
**Click “Go to next page”
**Measure the maximum amplitude of the S-wave for each seismogram and record your estimate
in the box below the seismogram.
29. Maximum S Wave Amplitude=
30. Maximum S Wave Amplitude=
31. Maximum S Wave Amplitude=
**Click “Submit to nomogram”
**Below is Richter's nomogram with three lines representing the data you provided. Use this
diagram and estimate the Richter magnitude of this earthquake. (Your three lines might not cross
at a point on the magnitude scale.) Enter your estimate in the box below the nomogram.
32. My estimate for the Richter magnitude of this earthquake =
**Click “Confirm magnitude”
Its ACTUAL estimated magnitude was __________.
**Enter your information for the certificate. Check the box that says Email Teacher, then enter
my email [email protected] . Click “Get certificate” and call me over when you
are finished to show me your final data table.
```