 |
Earthquake 4
posted February 21, 2000
as a Math
Forum EPoW
|
Introduction: In the Earthquake problem series, students play
the role of a scientist trying to
determine the location of the epicenter
of an earthquake.
|
|
Where’s the Math: In this
problem, students find the location
of the epicenter of an earthquake
by interpreting graphs of P and
S wave time differences over distance
and applying these to a map of the
area.
Standards: Algebra,
measurement
Role of Components: The
Earthquake problem series uses World
to animate the motion of characters
against the background image. Graph
works with simple function
to plot distance over time, which
is controlled with simple
clock and monitored with time
label. Instructions are displayed
and solutions are entered in a
text entry box.
|
|
|
Try the applet!
top
Sample submitted
solution:
From: Ryan,
age 14
Mac, age 14
School: Issaquah Middle School, Issaquah,
Washington
1. What is the distance from each seismograph
(S1, S2, S3) to the epicenter? (Hint: Use
the graph.)
Station one is 13 miles away from the epicenter,
station 2 is about 12 miles away from the
epicenter, and station 3 is about 14 miles
away from the epicenter.
2. Enter these distances in the boxes
labeled S1 Distance, S2 Distance, & S3 Distance.
Notice that the radius of each circle adjusts.
Where is the epicenter? How can you tell?
The epicenter is just a little bit above
the Town Dump, we can tell because it is
where all three P&S waves meet.
3. (BONUS) Last week, we determined
that data from one seismograph can only
determine the circle along which the epicenter
must lie. This week, we found that data
from three seismographs gives an exact location.
What could you learn from only 2 seismographs?
How about 4 or more?
[no answer provided]
top
|
|
Reflections:
Most students got the first two questions
right. For question 1, some answers were
approximated, and that was okay. Sometimes,
though, the order of the numbers were wrong,
considering that they are all found on line
whose slope is > 0. It's true that it was
difficult to read the precise numbers from
the graph, but they should get the order
of the numbers correct. That is, all 3 numbers
should be greater or equal to 12 and less
than 15 AND go in this order: s2->s1->s3.
For question 2, most students, if not all,
got this right. But their explanations were
not always good enough. Some students didn't
talk about circles and some talked about
diameters and other things that didn't seem
that relevant to the solution. For the bonus
question, about half of the submissions
got this right. The common mistakes were
to think that 4 seismographs would give
you more information than 3 seismographs,
and that 2 seismographs would give you an
area of possible locations of the epicenter.
I was especially impressed with the students
who realized that any more than 3 seismographs
would give you the same information as 3
seismographs. There didn't seem to be transference
between what the graph showed and how the
student would interact with the problem.
When I (Suzanne) tried the problem myself
I ignored the graph and just started playing
with the 3 values until they all intersected.
top
|
|
|
|
|
