Why do you need 3 seismographs to locate an epicenter

Science Lab 101

EXERCISE 1 DATA SHEET

Table 1. Earthquake Triangulation via Three Seismograph Stations

HKPS

INCN

MAJO

Latitude (DD)

22.28

37.48

36.55

Longitude (DD)

114.14

126.62

138.20

Earthquake Occurrence (UTC)

03:25:34

03:25:34

03:25:34

P-wave Arrival Time (UTC)

03:32

03:28

03:27

S-wave Arrival Time (UTC)

03:37

03:31

03:28

S-P Time Difference (UTC)

5 mins

2 mins

1 min

Distance From Epicenter (km)

3500

2000

500

EXERCISE 1 DATA SHEET

1. What is the latitude and longitude of your epicenter?

Latitude: ______32.38°__________

Longitude: ______148.24°________

2. Based on your results, would it be more or less beneficial to use more than three seismograph stations?

Answer: It is easier to find out the epicenter by comparison of triangulation result of we use more than three seismograph stations.

3. Select the link here to download and run the Earth’s Tectonic Plates.kmz file in Google Earth™. Is the epicenter near a plate boundary? Circle the correct answer.

Answer: YES NO

4. What type of plate boundary is located near the epicenter?

A. Convergent

B. Divergent

C. Transform

D. The epicenter is not near a plate boundary

Answer: A

5. How do P- and S-waves, respectively, move through the Earth? Draw lines in the circles to show the movement.

6. Read the information about tsunamis and faults below, then complete the related activities:

Tsunamis are formed as a result of sudden displacement of a large volume of water by significant vertical motion on a fault at the bottom of a volume of water.

Label the different types faults and then hypothesize which are the most likely to generate tsunamis.

Normal Fault Reverse Fault Strike-slip Fault

Hypothesis:

Reverse fault is most likely to generate Tsunami.

7. Click the link here to download and run the Hazards.kmz file in Google Earth™. Select “Tsunami Source Events”, “Tsunami Observations”, “Significant Earthquakes”, and “Significant Volcanic Eruptions.” Do you see any relationships among earthquakes, volcanoes, and tsunamis? Explain why or why not.

Answer: Earthquakes, volcanoes and tsunamis do have relationships. Usually, Earthquakes or volcanic could trigger tsunamis. In history, almost all the major tsunamis are trigger by earthquakes. Most volcanoes are along the edges of tectonic plates. Most earthquakes beneath a volcano could cause the movement of magma. The eruption of the volcano must cause an earthquake, because the intense magma activity can impact the surface of the earth's crust and lead to varying degrees of tectonic change in the lithosphere.