PhET Activity for MS-ESS3-2: Earthquake

DIRECTIONS:
1. Click on the 'Execute VirtualEarthquake' button in the center of the page.
Read the introductory text on the first page. Do not select a region yet. Get familiar with the terms P-wave, S-wave, and seismogram.

QUESTION: Are you acquainted with the tools in this simulation?

DIRECTIONS:
1. Scroll down to the bottom of the page.
2. Click the 'Japan region' radio button.
3. Click the 'Submit Choice' button located at the bottom right.

QUESTION: Why is it important for seismologists to have a network of seismic stations spread across different regions?

DIRECTIONS:
1. Click the 'View Seismograms' button at the bottom center of the page.

QUESTION: Looking at a seismogram, how can you distinguish the P-wave from the S-wave?

DIRECTIONS:
1. Remain on the page displaying the three seismograms.

QUESTION: A seismogram is a graph where the horizontal axis represents ___ and the vertical axis represents the ___ of the seismic waves.

(a)  

DIRECTIONS:
1. On the 'Pusan' seismogram, read the arrival time of the P-wave (the first wiggle).
2. Read the arrival time of the S-wave (the first large wiggle).
3. Subtract the P-wave time from the S-wave time to get the S-P interval.
4. Enter the calculated value of '50' into the input box for the 'Pusan' station.

QUESTION: The time difference between the P-wave and S-wave arrival is called the (a)   .

DIRECTIONS:
1. Do not change the value for Pusan. Now, visually compare the S-P interval (the time gap between the P and S waves) for all three stations.

QUESTION: A seismic station is located very far from an earthquake's epicenter. What would you expect the S-P interval on its seismogram to be compared to a station closer to the epicenter?

DIRECTIONS:
1. Now, enter the S-P interval for Tokyo as '30'.
2. Enter the S-P interval for Akita as '50'.
3. Click the 'Convert S-P Interval' button.

QUESTION: Explain in your own words why data from only one or two seismic stations is not enough to pinpoint the exact location of an earthquake's epicenter.

DIRECTIONS:
1. You should now be on the 'Epicentral Distance Determination' page (Page 4 of 12).

QUESTION: What fundamental relationship does the S-P travel-time graph illustrate?

DIRECTIONS:
1. Find your S-P interval for Pusan (50 seconds) on the vertical axis of the graph.
2. Follow the line horizontally to the right until it meets the curve.
3. From that point on the curve, follow the line vertically down to the horizontal axis to find the distance.
4. Following the video's incorrect measurement, enter '400' into the 'Epicentral Distance' box for Pusan.

QUESTION: According to the travel-time graph, as the epicentral distance increases, the S-P time interval also (a)   .

DIRECTIONS:
1. Use the travel-time graph to convert the S-P interval for Tokyo (30 seconds) and enter the video's value, '290', into the distance box.
2. Use the travel-time graph to convert the S-P interval for Akita (50 seconds) and enter the video's value, '110', into the distance box.
3. Click the 'Find Epicenter' button.

QUESTION: The simulation shows an 'Ooops!' message and three circles that do not intersect at a single point. What is the most likely cause of this result?