circular reasoning - the science of EQs
All EQ waves are not created equal.
P-Waves are faster than S-Waves
time delay
so the P-Waves get to the seismograph first.
And there is a wait for the S-Waves to arrive.
time = distance
the farther away the quake -- the longer the delay.
Ahh - time = distance.
distance = radii
once the distance is known -- a circle can be drawn with your laboratory at
its center, and this distance as the radius.
i'll get by with a little help from my friends
and when two other friends tell you how far away the quake occurred from
their laboratory --- the site of the EQ can be plotted.
The three circles intersect at the EQ
site.