The Scenario: A large earthquake has happened. You need to find the earthquakes epicenter to send help. The process of epicenter location has been used for over 50 years.

Steps to “Calculating an Epicenter” Step #1Calculate the S-P Interval (subtract) Step #2Use the Time/Distance chart to determine the distance in km. (Record Data) Step #3Measure the highest amplitude in mm. (Record Data) Step #4Using the nomogram, use the amplitude and distance to determine the magnitude. A ruler would be helpful in drawing a straight line. Step #5Use the distance from Step #2 along with the scale at the bottom of the map. Determine the correct distance on the compass and draw a circle around the appropriate seismic station.

Fresno, CA Seismic Station

Step #1 Calculate the S-P Interval (subtract) Station S-P IntervalDistanceAmplitude Fresno, CAseckmmm Las Vegas, NVseckmmm Phoenix, AZseckmmm P-Wave S-Wave This is the most important step try to be as accurate as possible. Record the number Here What is the number? 35 seconds 35 Fresno, CA Seismic Station S-P Interval

Step #2 Use the Time/Distance chart to determine the distance in km. (Record Data) The S-P Interval was 35 sec. Follow 35 across until it hits the S-P interval line, then follow it down to determine the distance. What is it? 340 km

Record the number Here Station S-P IntervalDistanceAmplitude Fresno, CA35 sec340 kmmm Las Vegas, NVseckmmm Phoenix, AZseckmmm

Step #3Measure the maximum amplitude in mm. (use the largest wave) (Record Data) Look Here And Here Record Here Station S-P IntervalDistanceAmplitude Fresno, CA 49 sec478 km mm Las Vegas, NVseckmmm Phoenix, AZseckmmm The number is?? 350 mm 350

Using the nomogram, use the amplitude and distance to determine the magnitude. A ruler would be helpful in drawing a straight line. Station S-P IntervalDistanceAmplitude Fresno, CA 35 sec340 km350 mm Las Vegas, NVseckmmm Phoenix, AZseckmmm

Station S-P IntervalDistanceAmplitude Fresno, CA35 sec340 km350 mm Las Vegas, NVseckmmm Phoenix, AZseckmmm Use the distance from Step #2 along with the scale at the bottom of the map. Determine the correct distance on the compass and draw a circle around the appropriate seismic station.

Fresno, CA Distance 340 km Don’t worry if it goes off the paper.