Name:________________________ Date:_______________
Grade and section:_______________ Score:______________
Activity 2
Find the Center
Objective:
a. Locate the epicenter of an earthquake using the triangulation method.
II. Procedure:
1. Study the data showing the difference in the arrival time of P-wave
and S-wave on three seismic recording stations.
Recording station Time difference in the arrival time of P-wave Distance of epicenter
and S-wave(seconds) from the station (km)
San Jose 32
El Nido 44
Dumaguete 40
2. Compute the distance of the epicenter from each of the stations
using this formula:
d = td x 100 km
8 seconds
Where: d = distance (km)
td = time difference in the arrival time of P-wave and S-wave (seconds)
This formula is suited because 8 seconds is the interval between the times of arrival of the P-wave and S- wave at a distance of 100
km.
3. Choose one of the recording stations and measure the computed distance on the map scale
(the scale of the map is 1.0 cm:100 km).This may vary. Set your compass for that computed distance.
4. Center your compass on the station you have chosen. Draw a circle.
5. Repeat steps 3 and 4 for the rest of the stations. You should get three circles that intersect or nearly intersect at a point. This intersection is the
epicenter.
Guide Questions:
1. What is the purpose of the triangulation method?
2. Where is the epicenter of this hypothetical earthquake?
3. What type of waves are used in determining the distance from the epicenter?
4. What will happen if data from only two stations are used in triangulation?
Name:________________________ Date:_______________
Grade and section:_______________ Score:______________
Activity 2
Find the Center
Objective:
a. Locate the epicenter of an earthquake using the triangulation method.
II. Procedure:
1. Study the data showing the difference in the arrival time of P-wave
and S-wave on three seismic recording stations.
Recording station Time difference in the arrival time of P-waveand Distance of epicenter
S-wave (seconds) from the station (km)
San Jose 32
El Nido 44
Dumaguete 40
2. Compute the distance of the epicenter from each of the stations
using this formula:
d = td x 100 km
8 seconds
Where: d = distance (km)
td = time difference in the arrival time of P-wave and S-wave (seconds)
This formula is suited because 8 seconds is the interval between the times of arrival of the P-wave and S- wave at a distance of 100
km.
3. Choose one of the recording stations and measure the computed distance on the map scale
(the scale of the map is 1.0 cm:100 km).This may vary. Set your compass for that computed
distance.
4. Center your compass on the station you have chosen. Draw a circle.
5. Repeat steps 3 and 4 for the rest of the stations. You should get three circles that intersect or
nearly intersect at a point. This intersection is the epicenter.
Guide Questions:
1. What is the purpose of the triangulation method?
2. Where is the epicenter of this hypothetical earthquake?
3. What type of waves are used in determining the distance from the epicenter?
4. What will happen if data from only two stations are used in triangulation?
