Name:____________________________ Grade & Section:_______ Score:_____
Teacher:__________________________ Date:__________________ Rating:____
Activity 1
Find the Center
Objective:
Locate the epicenter of an earthquake using the triangulation
method.
Materials:
• hypothetical records of earthquake waves
• Philippine map
• drawing compass and ruler
Procedure:
1. Study the data showing the difference in the arrival time of P-wave and S-
wave on three seismic recording stations.
2. Compute the distance of the epicenter from each of the stations using
this formula:
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 in Figure 3 is 1.5 cm: 200
km). 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.