(Q007) Of course, geologists don't know at first how far seismic waves have traveled or when they were generated by an earthquake. But as with the cars in this exercise, geologists do know (1) the velocities of the different types of seismic waves(2) that the waves started at the
same time (when the fault moved); and (3) the precise times when the different wave types were recorded by seismometers. To figure out
how far away an epicenter was and when the earthquake happened, we work backward to derive the information.
You can see how this works by continuing to use the two imaginary cars instead of seismic waves and working backward like a seismologist.
Imagine you are waiting for Car 1 and Car 2 to drive by a streetlight outside your window. You don't know where they came from or what
time they left, but you do know (1) their velocities (you have been told that Car 1 will arrive traveling at 1 mile in 60 seconds and Car 2 at 1
mile in 61 seconds) and (2) that they started at exactly the same time. As they drive by, you (3) record the precise delay between the times
they pass the streetlight outside your window.
Part 1.c. Using this information, how far did the two cars travel if Car2 passed the streetlight 25 seconds after Car 1? Write your answer in