#### A Math Forum Project

 ESCOT Problem of the Week: Archive of Problems, Submissions, & Commentary

Student Version

### Earthquake 3 - posted February 15, 2000

Try Earthquake 1 and Earthquake 2 before you do this problem.
Scientists can determine the epicenter of an earthquake using the difference in speed between the P and S waves. We can now use a graph to find the distance for any arrival time difference measured by a seismograph. We will use this graph to find the distance of the epicenter from a seismograph.

1. The time difference measured between P & S waves for an earthquake was 10 seconds. Use the graph to find how far the epicenter was from the seismograph.

2. Using the distance found in question 1, which of the following are possible locations for the epicenter: Town Dump, Highway, River Bend, City Hall, School, and/or the Park? (Hint: You can drag the epicenter to find the place or places where the distance matches the answer for question 1.)

3. Describe as carefully as you can all the possible locations of the earthquake.

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This problem seemed to be pretty straightforward for many students. Most people got questions 1 and 2 correct. Question 3 was a little harder in that some people didn't realize that the 5 miles they found for question 1 told us that the epicenter could be around the perimeter of a circle with the seismograph as its center and 5 miles as its radius, but a lot of students did solve that.

Common mistakes for question 3 included saying that the epicenter was within a 5-mile radius of the seismograph, or just giving the locations again.

This is an appropriate problem, perhaps on the simple side, for a one- week activity. It was pretty straightforward to mentor and many students received credit.

There were some technical difficulties, however. The image map did not display, and students could not complete the problem without it.

### Highlighted solutions:

 From: Lisa C., age 13Hana B., age School: Issaquah Middle School, Issaquah, WA

```Page Week 3
1. The time difference measured between P & S waves for an earthquake was 10
seconds. Use the graph above to find how far away the epicenter was from the
seismograph:
According to the graph the epicenter would be 5 miles away from the
seismograph to get those results.
2. Using the distance found in question 1, which of the following are possible
locations for the epicenter: Town Dump, Highway, River Bend, City Hall,
School, and/or the Park? (Hint: You can drag the epicenter around to find the
place or places where the distance matches the answer for question 1.)
One possibility is th town dump because it's 5 miles away from the
seismograph.  The school and the highway are also other possibilities.  All of
the other landmarks aren't possible because they are either too close or too
far away.

3. Describe as carefully as you can all the possible locations of the
earthquake:
Everything along the five mile radius of the seismograph could be a
possible location for the epicenter.
------------------------------------
```

 From: Marissa B., age 13Allison C., age 12 School: Issaquah Middle School, Issaquah, WA

```Page Week 3
1. The time difference measured between P & S waves for an earthquake was 10
seconds. Use the graph above to find how far away the epicenter was from the
seismograph:
The epicenter was 5 miles from the seismograph when the interval between
the P&S waves was 10 seconds.

2. Using the distance found in question 1, which of the following are possible
locations for the epicenter: Town Dump, Highway, River Bend, City Hall,
School, and/or the Park? (Hint: You can drag the epicenter around to find the
place or places where the distance matches the answer for question 1.)
The Town Dump and the Highway are possible locations for the epicenter at
five miles.

3. Describe as carefully as you can all the possible locations of the
earthquake:
If we put a dot on all of the possible locations of the epicenter at five
miles, it would  appear to be a circle with a radius (from the seismograph to
the epicenter) of five miles.

------------------------------------
```

### 40 students received credit this week.

Alex B., age 12 - Issaquah Middle School, Issaquah, WA
Amy B., age 13 - Issaquah Middle School, Issaquah, WA
Andrew B., age 13 - Issaquah Middle School, Issaquah, WA
Christine B., age 13 - Issaquah Middle School, Issaquah, WA
Hana B., age - Issaquah Middle School, Issaquah, WA
Marissa B., age 13 - Issaquah Middle School, Issaquah, WA
Megan B., age 13 - Issaquah Middle School, Issaquah, WA
Ryan B., age 14 - Issaquah Middle School, Issaquah, WA
Allison C., age 12 - Issaquah Middle School, Issaquah, WA
Katharine C., age 12 - Issaquah Middle School, Issaquah, WA
Lisa C., age 13 - Issaquah Middle School, Issaquah, WA
Aaron D., age 12 - Issaquah Middle School, Issaquah, WA
David D., age 13 - Issaquah Middle School, Issaquah, WA
Andy E., age 13 - Issaquah Middle School, Issaquah, WA
Greg H., age 12 - Issaquah Middle School, Issaquah, WA
Jordan H., age 13 - Issaquah Middle School, Issaquah, WA
Phillip H., age 13 - Issaquah Middle School, Issaquah, WA
Jeffrey J., age 13 - Issaquah Middle School, Issaquah, WA
Katelyn J., age 13 - Issaquah Middle School, Issaquah, WA
Lindsay J., age - Issaquah Middle School, Issaquah, WA
Paul J., age 15 - Issaquah Middle School, Issaquah, WA
Albert Jin K., age 13 - Issaquah Middle School, Issaquah, WA
Kristi K., age 14 - Issaquah Middle School, Issaquah, WA
Tyler M., age 14 - Issaquah Middle School, Issaquah, WA
Tani O., age 12 - Issaquah Middle School, Issaquah, WA
Zachary R., age 13 - Issaquah Middle School, Issaquah, WA
Holly S., age 14 - Issaquah Middle School, Issaquah, WA
Jayna S., age 14 - Issaquah Middle School, Issaquah, WA
Paradie S., age - Issaquah Middle School, Issaquah, WA
Scott S., age 14 - Issaquah Middle School, Issaquah, WA
Johanna T., age 14 - Issaquah Middle School, Issaquah, WA
Kaite T., age 13 - Issaquah Middle School, Issaquah, WA
Sei T., age 12 - Issaquah Middle School, Issaquah, WA
Dale V., age 13 - Issaquah Middle School, Issaquah, WA
Andrew W., age 13 - Issaquah Middle School, Issaquah, WA
Ella W., age 13 - Issaquah Middle School, Issaquah, WA
Kirsten W., age 12 - Issaquah Middle School, Issaquah, WA
Mac W., age 14 - Issaquah Middle School, Issaquah, WA
Matthew W., age 13 - Issaquah Middle School, Issaquah, WA
Devon Y., age - Issaquah Middle School, Issaquah, WA