Virtual Earthquake Lab 10 24 13

Virtual Earthquake Lab
Go to:
and answer the following questions.
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 "_____________________" 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 =
14. S-P Interval =
15. S-P Interval =
**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.
**Click “Find Epicenter”
S-P Interval
Epicentral Distance
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
_____ km
_____ km
_____ km
19. The location of the epicenter determined from your measurements of S-P intervals "should" 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.