Interview with Thomas A. Tombrello - Caltech Oral Histories

Tombrello–240
If you start doing carefully controlled experiments, you begin to realize the difference between
noise and data. In this case, although the signal was very small, we’re pretty sure we saw it. Our
hope was that if you had this network out there, along fault lines where nothing had moved for a
while but which had a history of seismic activity, you could localize areas that were much more
likely to have an earthquake. What you wanted to do was have enough instruments out in the
field so that when this fault broke, you would have a history of events and signals leading up to it
that basically could be interpreted as precursors. If you saw those same signals at other places
and no earthquake had appeared, you would know that maybe there was another cause, and so
on. The real chagrin we had was that the program got terminated because they moved almost all
the earthquake-prediction research stuff to Parkfield. But it was the same philosophy: Here is
something that breaks on a regular basis, and we’re going to take all this data leading up to the
next time it breaks.
ASPATURIAN: They pretty much instrumented it up the wazoo.
TOMBRELLO: When they sort of terminated our program, I remember saying, “I’m going to be
the witch at the christening. I’m going to bring down a curse upon you. I’m going to say to you,
‘You’re going to go up to Parkfield and you’re going to sit there looking at nothing happening
for years.’” And that’s exactly what happened. There are probably a few people around that
think I really did curse the Parkfield program, because the fault has just sat there for a very long
time.
ASPATURIAN: It seemed like a good idea.
TOMBRELLO: It seemed like a brilliant idea—and it was the same idea as ours, but to put all your
eggs in that one basket struck me as being stupid. With our program, we were covering 10,000
square miles. Now, granted, not very densely. We were hoping to deepen our coverage. But we
were covering a lot of areas where there was a much higher probability of something happening,
and the interesting thing about it is that we knew that something was going to happen down
around Whittier Narrows. And maybe a year after they closed our network, they had that
magnitude 5.9 earthquake that occurred, I believe, in the fall [October] of 1987.
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