Unformatted text preview: we refer the interested reader to a course in Geology
or the U.S. Geological Survey’s Earthquake Hazards Program found here.) Our technique
works only for relatively small distances because we need to assume the Earth is ﬂat in order
to use hyperbolas in the plane.3 The P-waves (“P” stands for Primary) of an earthquake
in Sasquatchia travel at 6 kilometers per second.4 Station A records the waves ﬁrst. Then
Station B, which is 100 kilometers due north of Station A, records the waves 2 seconds later.
Station C, which is 150 kilometers due west of Station A records the waves 3 seconds after
that (a total of 5 seconds after Station A). Where is the epicenter?
7. The notion of eccentricity introduced for ellipses in Deﬁnition 7.5 in Section 7.4 is the same
for hyperbolas in that we can deﬁne the eccentricity e of a hyperbola as
e= distance from the center to a focus
distance from the center to a vertex (a) With the help of your classmates, explain why e > 1 for any hyperbola...
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