Name: ________________________________ Class: _____________ Date: _________

Comparing Two Earthquakes:

The 1906 San Francisco Earthquake and the 1989 Loma Prieta Earthquake

Using this worksheet as a guide, you will be comparing two earthquakes that occurred in California. From the data, you will be asked to provide a hypothesis of why these two earthquakes that occurred in close proximity had different effects.

1. First go to http://earthquake.usgs.gov/learning/topics/mag_vs_int.php and write the definitions for earthquake intensity and magnitude.

2. Go to http://quake.wr.usgs.gov/~dalessio/DLESE/compare.html and use the information to answer the questions below.

a) Compare the two maps of California at the top of the page. They indicate the shaking intensity of two earthquakes the 1989 Loma Prieta Earthquake is at the left and the 1906 San Francisco Earthquake to the right. The shaking of which earthquake was felt over the greater area?

Approximately how much more area (2 times, 5 times, twenty-five times, etc.) felt shaking during that earthquake?

3. Go to http://quake.wr.usgs.gov/recent/recent.html record the date and magnitude for the

a) 1989 Loma Prieta earthquake:

b) 1906 San Francisco earthquake:

c) Which one was "stronger?" What is the evidence for your answer?

4. Return to http://quake.wr.usgs.gov/~dalessio/DLESE/compare.html and scroll down to the next two Bay Area View Shake Maps.

a) Click on the 1989 Loma Prieta Earthquake map (on the left) to increase the size of the map.

       Locate Santa Rosa, what was the intensity?

       Locate Sacramento, what was the intensity?

       Locate Oakland, what was the intensity?

b) Now click on the 1906 San Francisco Earthquake map.

       Locate Santa Rosa, what was the intensity?

       Locate Sacramento, what was the intensity?

       Locate Oakland, what was the intensity?

c) Compare your data. Were the intensities the same for each earthquake? What do you think might account for the differences?

5. Scroll down to the animation map. Enlarge the map by clicking on it. Watch the animation several times. Describe as many of the differences between the two that you can. You may use the back of this page for your comparison.

6. Scroll down to the next map that shows rupture length. Compare the length of the red and blue lines. Which earthquake had the greater rupture length?

Use the scale bar to estimate the length of each of the rupture lengths:

a) 1989 Loma Prieta earthquake:

b) 1906 San Francisco earthquake:

If the rupture travels at 3 km per second, approximately how long did the 1906 earthquake last?

7. Scroll down to the last picture that compares the seismogram recording for the two earthquakes. How do they differ?

8. Using the additional information gained by the rupture length and earthquake magnitude, write a one-sentence statement that explains what determines the intensity of an earthquake.

DLESE Teaching Boxes | October 2005