1. 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

2. 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

3. The arrival time of the first earthquake P-wave at a seismograph station was 10:11:20(hours:minutes:seconds).
If the epicenter of the earthquake is 8000 km away, what was the approximate arrival time of the first S-wave from this earthquake?
(1) 10:02:00 (3) 10:20:40
(2) 10:09:20 (4) 10:32:00

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

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

6. 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

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”).
Travel time chart (edge of paper!) used to find unique location of epicenter distance.
01:40
900 Km

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.
Circle of correct distance drawn on map.
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.
Three circles are required to get location (one = distance, two = two possible locations).

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