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Activity 1

The document describes an activity to locate the epicenter of a hypothetical earthquake using triangulation based on data from three seismic recording stations. It provides the materials, procedure, and questions. The procedure involves computing the distance from each station using a formula relating time difference of P and S wave arrival to distance. Circles are drawn on a map centered at each station with the computed radius. The intersection of the circles indicates the epicenter. Determining the epicenter is important for understanding earthquake locations and plate tectonics.

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Daisy Soriano Prestoza
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2K views3 pages

Activity 1

The document describes an activity to locate the epicenter of a hypothetical earthquake using triangulation based on data from three seismic recording stations. It provides the materials, procedure, and questions. The procedure involves computing the distance from each station using a formula relating time difference of P and S wave arrival to distance. Circles are drawn on a map centered at each station with the computed radius. The intersection of the circles indicates the epicenter. Determining the epicenter is important for understanding earthquake locations and plate tectonics.

Uploaded by

Daisy Soriano Prestoza
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as DOC, PDF, TXT or read online on Scribd
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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.
Time difference in Computed distance from
the arrival time of P- Distance of epicenter the map in centimeter(cm)
Recording station
wave and S-wave from the station (km)
(seconds)
Batangas 49.07
Puerto Princesa 58.10
Davao 39.47
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 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.
Q1. Where is the epicenter of this hypothetical earthquake?

Q2. What difficulty will you encounter if you only have data from two
recording stations?

In the previous activity, the hypothetical earthquake happened locally, that is why
we use the formula stated in the procedure. But, if the earthquake took place at a far
greater distance, seismologists use the distance-time graph similar to the figure below in
determining the location of the epicenter.
Time (minutes)

Distance (km) from Epicenter

http://stream2.cma.gov.cn/pub/comet/Environment/TsunamiWarningSystems/comet/tsunami/
warningsystem/print.htm
Figure 4. Distance-time graph

The distance-time graph above shows that the S-P interval is about 10 minutes.

Q3. What is the distance of the epicenter from the seismic station?

Q4. What do you think is the importance of determining the epicenter of an


earthquake?
Determining the location of earthquake epicenters plays a vital role in laying the foundations of plate
tectonics. Let us see how early geologists used the plotted positions of earthquake epicenters throughout
the world in conceptualizing crustal movements.

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