Of all the professors over
the years Nick Ambraseys was my favorite. Greek by birth, he brought some Meditteranean sunshine into the lecture hall on those grey drizzly days of the mid sixties in
South Kensington. He made it clear that he thought things were pretty simple
and he invited us to see it that way too. “Particle velocity? You know that
already, maybe you just haven’t thought about it. If you can know the strength
of the rock, and the shear wave velocity doesn’t vary much, so…” and he would
turn to the blackboard and make a little sketch and it was just like he said,
easy. He liked solutions to problems too. He was working on a way to use steel
straps from packing crates to hold mud brick houses together, like something
you would see in years to come in “The Whole Earth Catalog”.Ambraseys was interested in the effects of earthquakes on dams and originated several of the ideas that became mainstream in seismic studies of dam safety in California in the 1970s, especially after the near catastrophe of the San Fernando dam failure. These included dynamic response
analysis and so-called sliding block analyses, both acknowleged Ambraseys' inspirations. But while Ambraseys kept it simple, so you could work it out on single page of a yellow pad, California, more specifically UC Berkeley, made it baroque. You weren't doing the real stuff unless you ran it through a mainframe computer. The problem with this is that it introduced all kinds of errors and uncertainties and the results sometimes flew in the face of common sense, though given the opaqueness of the process you could hardly figure out why. This became apparent to me in the late 1970s when I myself worked on a string of these studies with Tom Leps and Bruce Bolt for PG&E. My reversion to the Ambraseys style got me into all kinds of trouble, but that's another story.
Many years after London I went to see
Ambraseys in his office. He was retired then. “They let me keep my office but they
won’t let me smoke my pipe,” he grumbled, though he saw a kind of humor in it
all. “Next they’re going to ban it outside too. I don’t think it does any harm,
do you?”
He was meticulous
in his research on earthquakes in the middle east, he read and spoke half a dozen
languages, maybe more. He was not tolerant of shortcuts. His work drew on hundreds of years, even millennia, of merchants' and travellers' diaries and such, written in
Latin, Greek, Arabic, Farsi, Urdu among them, which he found in obscure places, studied, and often corrected
himself by careful comparisons with other records. In the 1970s and thereafter, beginning with Turkey, he showed that the long term rate
of earthquakes -- the crucial “a” parameter of the Gutenberg Richter equation
-- was unstable and could not be relied upon to predict the future.
It was said that once in the middle of a
conference presentation on North African seismicity -- which he was forced to attend, loathing conferences when he could be in the basement of some dusty library or mosque -- he walked up to the screen
showing a map with proposed isoseismals, pointed at a topographic feature and
asked why regionally prevailing strong ground motion was indicated as highly improbable there.
Because the instrumental evidence clearly shows a quiescent area, was the cool
reply by the presenter, who had no Arabic and did not realize that the feature at which Ambraseys was pointing was labelled “Earthquake Mountain” in that language.
Sitting in his smokeless office in the gathering dusk of a London afternoon I asked him what was the most interesting thing he had learned since I had studied under him forty years
ago.
“The follies of
statistical thinking,” he said. He would have refilled his pipe here. “An engineering professor commutes here from Putney, he has his own
special and secret route developed over the years, it takes him on average 33
minutes, with a standard deviation of ten minutes. He is proud of his ability to enjoy his morning coffee at home, leave one hour before
his lecture time and arrive in the lecture hall with a nice factor of safety. Then one fine spring morning it happens. I giant lorry gets stuck in one of the narrow ways that is part of the route and one of the cars in the long line that grew behind breaks down,
runs out of petrol I imagine. The professor is an hour late. A disgrace. That is what I have learned.”
I assumed that he was the professor.
