ACTIVITY NO. 1

FIND THE CENTER

OBJECTIVELocate the epicenter of an earthquake using the triangulation method.

MATERIALS•Hypothetical records of

earthquake waves•Philippine map•Drawing compass and

ruler

PROCEDURE1. Study the data showing

the difference in the arrival time of P-wave and S-wave on three seismic recording stations.

RECORD-ING

STATION

TIME DIFFERENCE

IN THE ARRIVAL

TIME OF P-WAVE AND

S-WAVE (Seconds)

DISTANCE OF

EPICENTER FROM THE

STATION (Km)

COMPUTED DISTANCE ON THE

MAP (Cm) (1 cm : 70

km)

BATANGAS 44.8PUERTO PRINCESA

32

DAVAO 38.4

2. Compute the distance of the epicenter from each of the stations using the formula:

d= Td x 100 km 8 secondsWhere: d = distance (km)

Td = time difference in the arrival time of P-wave and S-wave (seconds)

3. Choose one of the recording stations and measure the computed distance on the map scale ( the scale of the map is 1 cm: 70 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.

C:\Users\user\Documents\Downloads\Earthquake Epicenter Triangulation.mp4

QUESTIONSQ1.Where is the epicenter of this

hypothetical earthquake?Q2. What difficulty will you

encounter if you only have data from two recording stations?

Distance-Time Graph

0 2000 4000 6000 8000 100000

5

10

15

20

25

30

ps

The distance-time graph shows that 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?

RECORD-ING

STATION

TIME DIFFERENCE

IN THE ARRIVAL TIME

OF P-WAVE AND S-WAVE

(Seconds)

DISTANCE OF EPICENTER FROM THE

STATION (Km)

COMPUTED DISTANCE ON THE MAP (Cm) (1 cm : 70 km)

BATANGAS 44.8 560 8PUERTO PRINCESA

32 400 5.7

DAVAO 38.4 480 6.9

LET’S CHECK YOUR ANSWERS

Let’s check your answers!

Q1. Since the three circles drawn intersect in the sea near Negros, it is where the epicenter is.

Q2. Assuming that the two circles will intersect, the circle will intersect at two points. Therefore, there will be two locations that could possibly be the epicenter.

Let’s check your answers!

Q3. 9, 000 kmQ4. Locating earthquake epicenters will

pinpoint which fault lines are active. Usually, the less active fault line stores great amount of potential energy that could cause major earthquake once released. Therefore, places near fault lines that remain inactive for a long period of time are due to experience a major earthquake.