1. To Find The Epicenter of an Earthquake Using the Difference in Time Between the P and the S Wave Follow the Rainbow! NSF Funded CUNY GK-12 Science NOW Project Copyright David Stolarz, January 22, 2010

2. NSF Funded CUNY GK-12 Science NOW Project Station Arrival Time of P-Wave Arrival Time of the S-Wave P-S Wave Interval Distance to the Epicenter P-Wave Travel Time Origin Time of Earthquake A 08:16:0008:21:0000:05:00 3.6 x10 3 km 00:06:20 08:09:40 B 08:19:0008:26:0000:07:00 5.0 x10 3 km 00:08:2008:10:40 C 08:21:00 08:30:0000:09:00 7.6 x10 3 km 00:10:20 08:11:40 Using Scrap Paper Finding the Epicenter of an Earthquake Using the Difference in Time Between the P and the S Wave The Completed Process

3. Finding the Epicenter of an Earthquake Using the Difference in Time Between the P and the S Wave NSF Funded CUNY GK-12 Science NOW Project Station Arrival Time of P-Wave Arrival Time of the S-Wave P-S Wave Interval Distance to the Epicenter P-Wave Travel Time Origin Time of Earthquake A B C Fill out the chart below using the three seismograms and the chart on Page 11 of the Earth Science Reference Tables. Start Simple – Draw a Line Down From the P-Wave to the Time Scale

4. Finding the Epicenter of an Earthquake Using the Difference in Time Between the P and the S Wave NSF Funded CUNY GK-12 Science NOW Project Station Arrival Time of P-Wave Arrival Time of the S-Wave P-S Wave Interval Distance to the Epicenter P-Wave Travel Time Origin Time of Earthquake A B C Fill out the chart below using the three seismograms and the chart on Page 11 of the Earth Science Reference Tables. Judge what time the P-wave starts

5. Finding the Epicenter of an Earthquake Using the Difference in Time Between the P and the S Wave NSF Funded CUNY GK-12 Science NOW Project Station Arrival Time of P-Wave Arrival Time of the S-Wave P-S Wave Interval Distance to the Epicenter P-Wave Travel Time Origin Time of Earthquake A B C Fill out the chart below using the three seismograms and the chart on Page 11 of the Earth Science Reference Tables. 08:16 17 18 19 A Quarter after 8 O’Clock! And No Seconds! A zoom-in shows P-wave starting at approximately 08:16:00

6. Finding the Epicenter of an Earthquake Using the Difference in Time Between the P and the S Wave NSF Funded CUNY GK-12 Science NOW Project Station Arrival Time of P-Wave Arrival Time of the S-Wave P-S Wave Interval Distance to the Epicenter P-Wave Travel Time Origin Time of Earthquake A 08:16:00 B C Fill out the chart below using the three seismograms and the chart on Page 11 of the Earth Science Reference Tables. Put that value in the appropriate box

7. Finding the Epicenter of an Earthquake Using the Difference in Time Between the P and the S Wave NSF Funded CUNY GK-12 Science NOW Project Station Arrival Time of P-Wave Arrival Time of the S-Wave P-S Wave Interval Distance to the Epicenter P-Wave Travel Time Origin Time of Earthquake A 08:16:0008:21:00 B C Fill out the chart below using the three seismograms and the chart on Page 11 of the Earth Science Reference Tables. Repeat the same process for the S-wave.

8. Finding the Epicenter of an Earthquake Using the Difference in Time Between the P and the S Wave NSF Funded CUNY GK-12 Science NOW Project Station Arrival Time of P-Wave Arrival Time of the S-Wave P-S Wave Interval Distance to the Epicenter P-Wave Travel Time Origin Time of Earthquake A 08:16:0008:21:00 B C Fill out the chart below using the three seismograms and the chart on Page 11 of the Earth Science Reference Tables. 08:21:00 (S-Wave Time) -08:16:00 (P-Wave Time) Calculate the interval between the two wave arrivals at the seisomgraph

9. Finding the Epicenter of an Earthquake Using the Difference in Time Between the P and the S Wave NSF Funded CUNY GK-12 Science NOW Project Station Arrival Time of P-Wave Arrival Time of the S-Wave P-S Wave Interval Distance to the Epicenter P-Wave Travel Time Origin Time of Earthquake A 08:16:0008:21:0000:05:00 B C Fill out the chart below using the three seismograms and the chart on Page 11 of the Earth Science Reference Tables. 08:21:00 (S-Wave Time) -08:16:00 (P-Wave Time) 00:05:00 (Time Difference) ( 0 Hours, 5 Minutes, 0 Seconds ) Enter that time in the appropriate box

10. NSF Funded CUNY GK-12 Science NOW Project Station Arrival Time of P-Wave Arrival Time of the S-Wave P-S Wave Interval Distance to the Epicenter P-Wave Travel Time Origin Time of Earthquake A 08:16:0008:21:0000:05:00 B C Go to page 11 of your Earth Science Reference Tables for the chart shown above

11. NSF Funded CUNY GK-12 Science NOW Project Station Arrival Time of P-Wave Arrival Time of the S-Wave P-S Wave Interval Distance to the Epicenter P-Wave Travel Time Origin Time of Earthquake A 08:16:0008:21:0000:05:00 B C Use the P-S Wave time interval to figure out the distance to the epicenter

12. NSF Funded CUNY GK-12 Science NOW Project Station Arrival Time of P-Wave Arrival Time of the S-Wave P-S Wave Interval Distance to the Epicenter P-Wave Travel Time Origin Time of Earthquake A 08:16:0008:21:0000:05:00 B C Scrap Paper Place Marks at P-S Wave Interval Time and at 0. Create a reference measurement using scrap paper and the P-S Wave value

13. NSF Funded CUNY GK-12 Science NOW Project Station Arrival Time of P-Wave Arrival Time of the S-Wave P-S Wave Interval Distance to the Epicenter P-Wave Travel Time Origin Time of Earthquake A 08:16:0008:21:0000:05:00 B C Scrap Paper Slide paper up and over until the reference marks Line up with the P and S Lines. Find the proper place where the reference marks match the P and S Lines.

14. NSF Funded CUNY GK-12 Science NOW Project Station Arrival Time of P-Wave Arrival Time of the S-Wave P-S Wave Interval Distance to the Epicenter P-Wave Travel Time Origin Time of Earthquake A 08:16:0008:21:0000:05:00 B C Scrap Paper Lightly, make a reference mark in pencil on the reference table at this place on the P line. For convenience, make a light pencil mark on the P line for use in the next step

15. NSF Funded CUNY GK-12 Science NOW Project Station Arrival Time of P-Wave Arrival Time of the S-Wave P-S Wave Interval Distance to the Epicenter P-Wave Travel Time Origin Time of Earthquake A 08:16:0008:21:0000:05:00 B C Look straight down from the P line pencil mark and judge the epicenter distance..2. 4.6.8

16. NSF Funded CUNY GK-12 Science NOW Project Station Arrival Time of P-Wave Arrival Time of the S-Wave P-S Wave Interval Distance to the Epicenter P-Wave Travel Time Origin Time of Earthquake A 08:16:0008:21:0000:05:00 B C Lightly, make reference marks in pencil On the reference table at these two places. Enter that value for the epicenter distance with proper units.

17. NSF Funded CUNY GK-12 Science NOW Project Station Arrival Time of P-Wave Arrival Time of the S-Wave P-S Wave Interval Distance to the Epicenter P-Wave Travel Time Origin Time of Earthquake A 08:16:0008:21:0000:05:00 B C Look across at the y-axis to Judge the time value 00:06:40 00:06:20 Travel Time (minutes)

18. NSF Funded CUNY GK-12 Science NOW Project Station Arrival Time of P-Wave Arrival Time of the S-Wave P-S Wave Interval Distance to the Epicenter P-Wave Travel Time Origin Time of Earthquake A 08:16:0008:21:0000:05:00 00:06:20 B C Enter that value for the epicenter distance with proper units.

19. NSF Funded CUNY GK-12 Science NOW Project Station Arrival Time of P-Wave Arrival Time of the S-Wave P-S Wave Interval Distance to the Epicenter P-Wave Travel Time Origin Time of Earthquake A 08:16:0008:21:0000:05:00 00:06:20 B C ERASE YOUR MARK! Erase your pencil mark on the P-wave to keep your reference table clean

20. NSF Funded CUNY GK-12 Science NOW Project Station Arrival Time of P-Wave Arrival Time of the S-Wave P-S Wave Interval Distance to the Epicenter P-Wave Travel Time Origin Time of Earthquake A 08:16:0008:21:0000:05:00 00:06:20 B C 08:16:00 (P Arrival Time) 00:06:20 (P Travel Time) Calculate what time the earthquake happened using the Arrival and travel times

21. NSF Funded CUNY GK-12 Science NOW Project Station Arrival Time of P-Wave Arrival Time of the S-Wave P-S Wave Interval Distance to the Epicenter P-Wave Travel Time Origin Time of Earthquake A 08:16:0008:21:0000:05:00 00:06:20 B C 08:16:00 (P Arrival Time) - 00:06:20 (P Travel Time) MINUS! Obviously, the earthquake happened earlier than when its was felt miles away

22. NSF Funded CUNY GK-12 Science NOW Project Station Arrival Time of P-Wave Arrival Time of the S-Wave P-S Wave Interval Distance to the Epicenter P-Wave Travel Time Origin Time of Earthquake A 08:16:0008:21:0000:05:00 00:06:20 B C 08:15:60 (1 min. is 60 sec) 08:16:00 (P Arrival Time) - 00:06:20 (P Travel Time) Convert hours to minutes or minutes to seconds when necessary

23. NSF Funded CUNY GK-12 Science NOW Project Station Arrival Time of P-Wave Arrival Time of the S-Wave P-S Wave Interval Distance to the Epicenter P-Wave Travel Time Origin Time of Earthquake A 08:16:0008:21:0000:05:00 3.6 x10 3 km 00:06:20 08:09:40 B C 08:15:60 (1 min. is 60 sec) 08:16:00 (P Arrival Time) - 00:06:20 (P Travel Time) 08:09:40 (Time at Origin) Put the calculated time of earthquake in the proper box

24. NSF Funded CUNY GK-12 Science NOW Project Station Arrival Time of P-Wave Arrival Time of the S-Wave P-S Wave Interval Distance to the Epicenter P-Wave Travel Time Origin Time of Earthquake A 08:16:0008:21:0000:05:00 3.6 x10 3 km 00:06:20 08:09:40 B 08:19:0008:26:0000:07:00 5.0 x10 3 km 00:08:2008:10:40 C Using Scrap Paper Finding the Epicenter of an Earthquake Using the Difference in Time Between the P and the S Wave Anything complex is easier when broken into smaller steps

25. NSF Funded CUNY GK-12 Science NOW Project Station Arrival Time of P-Wave Arrival Time of the S-Wave P-S Wave Interval Distance to the Epicenter P-Wave Travel Time Origin Time of Earthquake A 08:16:0008:21:0000:05:00 3.6 x10 3 km 00:06:20 08:09:40 B08:19:00 C Finding the Epicenter of an Earthquake Using the Difference in Time Between the P and the S Wave Judge what time the P-wave starts and enter it in the box

26. NSF Funded CUNY GK-12 Science NOW Project Station Arrival Time of P-Wave Arrival Time of the S-Wave P-S Wave Interval Distance to the Epicenter P-Wave Travel Time Origin Time of Earthquake A 08:16:0008:21:0000:05:00 3.6 x10 3 km 00:06:20 08:09:40 B 08:19:00 08:26:00 C Finding the Epicenter of an Earthquake Using the Difference in Time Between the P and the S Wave Repeat the same process for the S-wave.

27. NSF Funded CUNY GK-12 Science NOW Project Station Arrival Time of P-Wave Arrival Time of the S-Wave P-S Wave Interval Distance to the Epicenter P-Wave Travel Time Origin Time of Earthquake A 08:16:0008:21:0000:05:00 3.6 x10 3 km 00:06:20 08:09:40 B 08:19:0008:26:00 00:07:00 C Finding the Epicenter of an Earthquake Using the Difference in Time Between the P and the S Wave Use the P-S Wave time interval to set reference marks for the sliding step

28. NSF Funded CUNY GK-12 Science NOW Project Station Arrival Time of P-Wave Arrival Time of the S-Wave P-S Wave Interval Distance to the Epicenter P-Wave Travel Time Origin Time of Earthquake A 08:16:0008:21:0000:05:00 3.6 x10 3 km 00:06:20 08:09:40 B 08:19:0008:26:0000:07:00 C Using Scrap Paper Finding the Epicenter of an Earthquake Using the Difference in Time Between the P and the S Wave Create a reference measurement using scrap paper and the P-S Wave value

29. NSF Funded CUNY GK-12 Science NOW Project Station Arrival Time of P-Wave Arrival Time of the S-Wave P-S Wave Interval Distance to the Epicenter P-Wave Travel Time Origin Time of Earthquake A 08:16:0008:21:0000:05:00 3.6 x10 3 km 00:06:20 08:09:40 B 08:19:0008:26:0000:07:00 C Using Scrap Paper Finding the Epicenter of an Earthquake Using the Difference in Time Between the P and the S Wave Find the proper place where the reference marks match the P and S Lines.

30. NSF Funded CUNY GK-12 Science NOW Project Station Arrival Time of P-Wave Arrival Time of the S-Wave P-S Wave Interval Distance to the Epicenter P-Wave Travel Time Origin Time of Earthquake A 08:16:0008:21:0000:05:00 3.6 x10 3 km 00:06:20 08:09:40 B 08:19:0008:26:0000:07:00 5.0 x10 3 km C Using Scrap Paper Finding the Epicenter of an Earthquake Using the Difference in Time Between the P and the S Wave Look straight down from the P line pencil mark and judge the epicenter distance.

31. NSF Funded CUNY GK-12 Science NOW Project Station Arrival Time of P-Wave Arrival Time of the S-Wave P-S Wave Interval Distance to the Epicenter P-Wave Travel Time Origin Time of Earthquake A 08:16:0008:21:0000:05:00 3.6 x10 3 km 00:06:20 08:09:40 B 08:19:0008:26:0000:07:00 5.0 x10 3 km 00:08:20 C Using Scrap Paper Finding the Epicenter of an Earthquake Using the Difference in Time Between the P and the S Wave Look across at the y-axis to Judge the time value

32. NSF Funded CUNY GK-12 Science NOW Project Station Arrival Time of P-Wave Arrival Time of the S-Wave P-S Wave Interval Distance to the Epicenter P-Wave Travel Time Origin Time of Earthquake A 08:16:0008:21:0000:05:00 3.6 x10 3 km 00:06:20 08:09:40 B 08:19:0008:26:0000:07:00 5.0 x10 3 km 00:08:20 08:10:40 C Using Scrap Paper Finding the Epicenter of an Earthquake Using the Difference in Time Between the P and the S Wave Put the calculated time of earthquake in the proper box

33. NSF Funded CUNY GK-12 Science NOW Project Station Arrival Time of P-Wave Arrival Time of the S-Wave P-S Wave Interval Distance to the Epicenter P-Wave Travel Time Origin Time of Earthquake A 08:16:0008:21:0000:05:00 3.6 x10 3 km 00:06:20 08:09:40 B 08:19:0008:26:0000:07:00 5.0 x10 3 km 00:08:2008:10:40 C Using Scrap Paper Finding the Epicenter of an Earthquake Using the Difference in Time Between the P and the S Wave Anything complex is easier when broken into smaller steps

34. NSF Funded CUNY GK-12 Science NOW Project Station Arrival Time of P-Wave Arrival Time of the S-Wave P-S Wave Interval Distance to the Epicenter P-Wave Travel Time Origin Time of Earthquake A 08:16:0008:21:0000:05:00 3.6 x10 3 km 00:06:20 08:09:40 B 08:19:0008:26:0000:07:00 5.0 x10 3 km 00:08:2008:10:40 C 08:21:00 08:30:0000:09:00 7.6 x10 3 km 00:10:20 08:11:40 Using Scrap Paper Finding the Epicenter of an Earthquake Using the Difference in Time Between the P and the S Wave Follow the same overall process for Station C

35. NSF Funded CUNY GK-12 Science NOW Project Station Arrival Time of P-Wave Arrival Time of the S-Wave P-S Wave Interval Distance to the Epicenter P-Wave Travel Time Origin Time of Earthquake A 08:16:0008:21:0000:05:00 3.6 x10 3 km 00:06:20 08:09:40 B 08:19:0008:26:0000:07:00 5.0 x10 3 km 00:08:2008:10:40 C 08:21:00 Finding the Epicenter of an Earthquake Using the Difference in Time Between the P and the S Wave Judge what time the P-wave starts and enter it in the box

36. NSF Funded CUNY GK-12 Science NOW Project Station Arrival Time of P-Wave Arrival Time of the S-Wave P-S Wave Interval Distance to the Epicenter P-Wave Travel Time Origin Time of Earthquake A 08:16:0008:21:0000:05:00 3.6 x10 3 km 00:06:20 08:09:40 B 08:19:0008:26:0000:07:00 5.0 x10 3 km 00:08:2008:10:40 C 08:21:00 08:30:00 Finding the Epicenter of an Earthquake Using the Difference in Time Between the P and the S Wave Repeat the same process for the S-wave.

37. NSF Funded CUNY GK-12 Science NOW Project Station Arrival Time of P-Wave Arrival Time of the S-Wave P-S Wave Interval Distance to the Epicenter P-Wave Travel Time Origin Time of Earthquake A 08:16:0008:21:0000:05:00 3.6 x10 3 km 00:06:20 08:09:40 B 08:19:0008:26:0000:07:00 5.0 x10 3 km 00:08:2008:10:40 C 08:21:00 08:30:00 00:09:00 Finding the Epicenter of an Earthquake Using the Difference in Time Between the P and the S Wave Use the P-S Wave time interval and the y axis of the reference table

38. NSF Funded CUNY GK-12 Science NOW Project Station Arrival Time of P-Wave Arrival Time of the S-Wave P-S Wave Interval Distance to the Epicenter P-Wave Travel Time Origin Time of Earthquake A 08:16:0008:21:0000:05:00 3.6 x10 3 km 00:06:20 08:09:40 B 08:19:0008:26:0000:07:00 5.0 x10 3 km 00:08:2008:10:40 C 08:21:00 08:30:0000:09:00 Using Scrap Paper Finding the Epicenter of an Earthquake Using the Difference in Time Between the P and the S Wave Create a reference measurement using scrap paper and the P-S Wave time value

39. NSF Funded CUNY GK-12 Science NOW Project Station Arrival Time of P-Wave Arrival Time of the S-Wave P-S Wave Interval Distance to the Epicenter P-Wave Travel Time Origin Time of Earthquake A 08:16:0008:21:0000:05:00 3.6 x10 3 km 00:06:20 08:09:40 B 08:19:0008:26:0000:07:00 5.0 x10 3 km 00:08:2008:10:40 C 08:21:00 08:30:0000:09:00 Using Scrap Paper Finding the Epicenter of an Earthquake Using the Difference in Time Between the P and the S Wave Find the proper place where the reference marks match the P and S Lines.

40. NSF Funded CUNY GK-12 Science NOW Project Station Arrival Time of P-Wave Arrival Time of the S-Wave P-S Wave Interval Distance to the Epicenter P-Wave Travel Time Origin Time of Earthquake A 08:16:0008:21:0000:05:00 3.6 x10 3 km 00:06:20 08:09:40 B 08:19:0008:26:0000:07:00 5.0 x10 3 km 00:08:2008:10:40 C 08:21:00 08:30:0000:09:00 7.6 x10 3 km Using Scrap Paper Finding the Epicenter of an Earthquake Using the Difference in Time Between the P and the S Wave Enter that value for the epicenter distance with proper units.

41. NSF Funded CUNY GK-12 Science NOW Project Station Arrival Time of P-Wave Arrival Time of the S-Wave P-S Wave Interval Distance to the Epicenter P-Wave Travel Time Origin Time of Earthquake A 08:16:0008:21:0000:05:00 3.6 x10 3 km 00:06:20 08:09:40 B 08:19:0008:26:0000:07:00 5.0 x10 3 km 00:08:2008:10:40 C 08:21:00 08:30:0000:09:00 7.6 x10 3 km 00:10:20 Using Scrap Paper Finding the Epicenter of an Earthquake Using the Difference in Time Between the P and the S Wave Calculate what time the earthquake happened using the Arrival and travel times

42. NSF Funded CUNY GK-12 Science NOW Project Station Arrival Time of P-Wave Arrival Time of the S-Wave P-S Wave Interval Distance to the Epicenter P-Wave Travel Time Origin Time of Earthquake A 08:16:0008:21:0000:05:00 3.6 x10 3 km 00:06:20 08:09:40 B 08:19:0008:26:0000:07:00 5.0 x10 3 km 00:08:2008:10:40 C 08:21:00 08:30:0000:09:00 7.6 x10 3 km 00:10:20 08:11:40 Using Scrap Paper Finding the Epicenter of an Earthquake Using the Difference in Time Between the P and the S Wave Calculate and place the time of earthquake in the proper box

43. NSF Funded CUNY GK-12 Science NOW Project Finding the Epicenter of an Earthquake Using the Difference in Time Between the P and the S Wave 7600 km 3600 km All three arcs must pass through the earthquake epicenter, in this case, the San Andreas fault in California, USA. Using scrap paper. Use the Station info to locate the epicenter of the earthquake on a map

44. NSF Funded CUNY GK-12 Science NOW Project Station Arrival Time of P-Wave Arrival Time of the S-Wave P-S Wave Interval Distance to the Epicenter P-Wave Travel Time Origin Time of Earthquake A 08:16:0008:21:0000:05:00 3.6 x10 3 km 00:06:20 08:09:40 B 08:19:0008:26:0000:07:00 5.0 x10 3 km 00:08:2008:10:40 C 08:21:00 08:30:0000:09:00 7.6 x10 3 km 00:10:20 08:11:40 Finding the Epicenter of an Earthquake Using the Difference in Time Between the P and the S Wave On the Station Map, Find Station A

45. NSF Funded CUNY GK-12 Science NOW Project Station Arrival Time of P-Wave Arrival Time of the S-Wave P-S Wave Interval Distance to the Epicenter P-Wave Travel Time Origin Time of Earthquake A 08:16:0008:21:0000:05:00 3.6 x10 3 km 00:06:20 08:09:40 B 08:19:0008:26:0000:07:00 5.0 x10 3 km 00:08:2008:10:40 C 08:21:00 08:30:0000:09:00 7.6 x10 3 km 00:10:20 08:11:40 Finding the Epicenter of an Earthquake Using the Difference in Time Between the P and the S Wave Find Station B

46. NSF Funded CUNY GK-12 Science NOW Project Station Arrival Time of P-Wave Arrival Time of the S-Wave P-S Wave Interval Distance to the Epicenter P-Wave Travel Time Origin Time of Earthquake A 08:16:0008:21:0000:05:00 3.6 x10 3 km 00:06:20 08:09:40 B 08:19:0008:26:0000:07:00 5.0 x10 3 km 00:08:2008:10:40 C 08:21:00 08:30:0000:09:00 7.6 x10 3 km 00:10:20 08:11:40 Finding the Epicenter of an Earthquake Using the Difference in Time Between the P and the S Wave Find Station C

47. NSF Funded CUNY GK-12 Science NOW Project Station Arrival Time of P-Wave Arrival Time of the S-Wave P-S Wave Interval Distance to the Epicenter P-Wave Travel Time Origin Time of Earthquake A 08:16:0008:21:0000:05:00 3.6 x10 3 km 00:06:20 08:09:40 B 08:19:0008:26:0000:07:00 5.0 x10 3 km 00:08:2008:10:40 C 08:21:00 08:30:0000:09:00 7.6 x10 3 km 00:10:20 08:11:40 Distance to the Epicenter 3.6 x10 3 km 5.0 x10 3 km 7.6 x10 3 km Finding the Epicenter of an Earthquake Using the Difference in Time Between the P and the S Wave Station A B C Use the Distance to Epicenter for each station

48. NSF Funded CUNY GK-12 Science NOW Project Station Arrival Time of P-Wave Arrival Time of the S-Wave P-S Wave Interval Distance to the Epicenter P-Wave Travel Time Origin Time of Earthquake A 08:16:0008:21:0000:05:00 3.6 x10 3 km 00:06:20 08:09:40 B 08:19:0008:26:0000:07:00 5.0 x10 3 km 00:08:2008:10:40 C 08:21:00 08:30:0000:09:00 7.6 x10 3 km 00:10:20 08:11:40 Distance to the Epicenter 3.6 x10 3 km 5.0 x10 3 km 7.6 x10 3 km Distance to the Epicenter 3,600 km 5,000 km 7,600 km or Finding the Epicenter of an Earthquake Using the Difference in Time Between the P and the S Wave Station A B C Convert scientific notation for the distance to the epicenter for each station

49. NSF Funded CUNY GK-12 Science NOW Project Finding the Epicenter of an Earthquake Using the Difference in Time Between the P and the S Wave Using the scale bar below as the reference, scribe a circle around the three points using a compass, string, or scrap paper. 3600 km Distance to the Epicenter 3,600 km 5,000 km 7,600 km Station A B C Scribe the arc for Station A using the map scale distance

50. NSF Funded CUNY GK-12 Science NOW Project Finding the Epicenter of an Earthquake Using the Difference in Time Between the P and the S Wave The two circles cross at two points. A third circle is needed to confirm the earthquake epicenter. 5000 km Distance to the Epicenter 3,600 km 5,000 km 7,600 km Station A B C Scribe the arc for Station B using the map scale distance

51. NSF Funded CUNY GK-12 Science NOW Project Finding the Epicenter of an Earthquake Using the Difference in Time Between the P and the S Wave 7600 km 3600 km All three arcs must pass through the earthquake epicenter, in this case, the San Andreas fault in California, USA. Using scrap paper. Distance to the Epicenter 3,600 km 5,000 km 7,600 km Station A B C If the distance is longer than the scale, use scrap paper to extend the scale.

52. NSF Funded CUNY GK-12 Science NOW Project Finding the Epicenter of an Earthquake Using the Difference in Time Between the P and the S Wave 7600 km 3600 km All three arcs must pass through the earthquake epicenter, in this case, the San Andreas fault in California, USA. Using scrap paper. Where the three arcs cross is the epicenter – Circle it!