1. So why are seismograms so important?

2. Magnitude deduced from vibration.
Magnitudes from 0 – 10.

3. Magnitudes from 0 to 10 6 10

4. P waves arrive before S waves.
Time (origin) and epicenter of the earthquake are deduced from arrival time difference.

5. The farther from an earthquake’s epicenter the greater the arrival difference between P and S Waves.

6. Figuring out arrival times means we need to add time!
Difference in arrival times is 30 seconds.
What is the epicenter distance for 30 seconds of “arrival time difference”?
10 sec
40 sec

9. If you know the time, chart will tell you the distance and visa versa.
Time = Distance!
If you know the time, chart will tell you the distance and visa versa.

10. How far does a P-wave travel in 7 minutes?
The seismogram shows an earthquake P-wave arrival time in Albany, NY.
How far does a P-wave travel in 7 minutes?
If the earthquake occurred at 10:00 p.m., how far from the earthquake epicenter was Albany, NY?
1,900 km (3) 3,200 km
(2) 4,000 km (4) 5,200 km

11. A seismic station receives an earthquake’s P-wave at 16:30:00 (4:30 pm). What is the origin time if the P-wave travelled 5600 Km?
16:30:00
– :00
= 16:21:00
4:21 pm!

13. 00:01:15
00:02:55
00:07:10
00:02:30
00:09:20
00:05:11
00:14:35
00:07:07
00:00:45
00:01:05
00:06:20
00:01:20
00:08:22
00:04:11
00:06:15
00:04:30