1. 4 min of arrival difference = 2,600 km
According to the seismogram, how far is this seismic station from the epicenter?
4 min of arrival difference = 2,600 km

2. 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

3. When does the P wave arrive? 08:08:00
The seismogram was recorded at a seismic station and shows the arrival times of the first P-wave and S-wave from an earthquake.
When does the P wave arrive?
08:08:00
When does the S wave arrive?
08:11:25
What is the difference in arrival times?
00:03:25
What is the distance to the epicenter?
2100 Km
When was the earthquake?
For Km a P-Wave takes 4:10, so…
08:03:50

4. How do we locate an epicenter?

5. How do we locate an epicenter?
Earthquake occurs (originates), waves spread.

6. How do we locate an epicenter?
Earthquake occurs (originates), waves spread.
P & S waves arrive at a seismometer.

7. How do we locate an epicenter?
Earthquake occurs (originates), waves spread.
P & S waves arrive at a seismometer.
P arrival is subtracted from S arrival to determine arrival difference (“lag time”).
S wave :44:50
P wave :43:10
01:40

8. How do we locate an epicenter?
Earthquake occurs (originates), waves spread.
P & S waves arrive at a seismometer.
P arrival is subtracted from S arrival to determine arrival difference (“lag time”).
Travel time chart (edge of paper!) used to find unique location of epicenter distance.
01:40
900 Km

9. How do we locate an epicenter?
Earthquake occurs (originates), waves spread.
P & S waves arrive at a seismometer.
P arrival is subtracted from S arrival to determine arrival difference (“lag time”).
Travel time chart (edge of paper!) used to find unique location of epicenter distance.
Circle of correct distance drawn on map.
900 Km

10. How do we locate an epicenter?
Earthquake occurs (originates), waves spread.
P & S waves arrive at a seismometer.
P arrival is subtracted from S arrival to determine arrival difference (“lag time”).
Travel time chart (edge of paper!) used to find unique location of epicenter distance.
Circle of correct distance drawn on map.
Three circles are required to get location (one = distance, two = two possible locations).

11. The diagram here was completed by a seismologist.
The earthquake’s epicenter is closest to location
(1) A (3) C
(2) B (4) D