1. Lab Practical Review Day 2
A. Earthquakes: Locating an Epicenter
B. Astronomy: Constructing and Analyzing an elliptical orbit

2. Locating an Epicenter
1.) Using a seismogram, write down the arrival of the P and the S wave
2.) Find the S-P interval (subtract time difference between arrival times) – here it would be 00:04:00 – 4 minutes

3. 3.) Mark this time interval on a scrap piece of paper using the y-axis in your ESRT pg. 10
4.) Slide this piece of paper over until the time interval fits exactly between the P and S waves on the chart.
For example if the S-P interval was 05:25, the distance to the epicenter would be ~3,800 km

4. Draw the distance to the epicenter using your compass
Ex: Your seismic station was in San Francisco, with a found distance of 2,800 km to epicenter.
Mark set distance on map from station using your scrap
Mark distance on scrap using map scale
Draw circle!-put pencil in the closest opening to your mark!

5. Example of what a finished map looks like

6. Eccentricity
Eccentricity defines how eccentric (stretched out) an orbit is and is defined by the equation e = d/L (pg. 1 ESRT)
Eccentricity has values between 0-1 (NO UNITS)
Values closer to 0= less eccentric.
Values closer to 1= more eccentric.

7. Calculating Eccentricity After Drawing your Ellipse

8. Comparing your calculated eccentricity to known eccentricities of planets