12. Using the Option settings (gear symbol on the upper right), switch to 30 Days, Significant Worldwide and zoom out to the World. Where did the two strongest of these earthquakes occur and what was their magnitude? (3) 13. Switch to 30 Days, Magnitude 4.5+ U. S. What can you say about the pattern of these significant earthquakes across the world? (2)

14. Zoom to California (click on the globe icon beneath the +/- zoom buttons). Switch to 7 Days, Magnitude 2.5+ U. S. Turn on the U. S. Faults layer. What pattern do you notice in the distribution of earthquakes in the western U. S.? (2)

15. Where did the strongest of these earthquakes occur in the western U. S. and what was its magnitude? (2)

16. Go to the USGS "How Much Bigger…?" Calculator (Links to an external site.). Enter the magnitude of the strongest earthquake you found in the previous question. How much stronger (by energy released) was this earthquake than a 2.5 magnitude earthquake (one which is barely perceptible to humans). (2)

17. Earthquakes occur at faults. How does slippage at a fault result in an earthquake? See p. 436 and Figure 14-58 in your textbook. (2)

18. Zoom to North America (use the "Zoom to U. S." option). How many "Significant" earthquakes have occurred in North America in the last 30 days (use the 30 days, Significant Worldwide option)? Where have these earthquakes occurred? If near a plate boundary name the type of plate boundary (you should look this up). (3)

19. Switch to 7 Days, Magnitude 2.5+ U. S. Have any 2.5+ magnitude earthquakes occurred away from plate boundaries? Where? (2) What are the best explanations for the occurrence of these specific earthquakes (you should look this up)? (bonus +1)