Geoscience Reference
In-Depth Information
scientific expertise and common experience, with implications for public
discussions of science today.
1
At the same time, the built environment of the twentieth century was be-
coming increasingly vulnerable to devastating accidents triggered by natural
hazards. By the 1970s, the realization was dawning that many complex feats
of recent engineering—bridges, dams, skyscrapers, freeways, and, above all,
nuclear reactors—had not been reinforced against earthquakes.
2
It was also
becoming clear to a small group of engineers and seismologists that local
seismic risk could not be evaluated on the basis of instrumental records
alone. Seismographs have not been around long enough to give an accu-
rate picture of a region's seismicity over time. Accelerometers can provide
mechanical parameters that are easy to plug into engineers' equations, but
they say nothing about future damage. Knowing the value of “peak ground
acceleration” during past tremors won't tell you how many buildings are
likely to collapse in the next one. The better measure of seismic risk is inten-
sity, calculated from the observed effects of shaking. Intensity is a scientific
measure of “actual earthquake experience”; it is therefore the best predictor
of the human impact of future events.
3
It was not easy, however, to revive the organization and habits of earth-
quake observing in the late twentieth century. The British were not alone
in finding that the public had “other things on their mind” (chapter 2).
Institutional memories of earthquake-observing networks survived in some
places, but many of the lessons learned through their day-to-day operation
had been forgotten. “One thing is sure,” recalls the Ljubljana seismologist
Ina Ceci´, “the lack of written information about macroseismology in gen-
eral was huge; this was something that was simply not discussed, and was
considered to be simple and clear, but everybody had a different way how to
deal with things. This goes both for data evaluation and data collection.”
In May 1989, six months before the fall of the Berlin Wall, scientists
from Yugoslavia, Austria, Hungary, and Italy gathered in a village in Slo-
venia to discuss—in English—macroseismic methodology. Since the collapse
of the Austro-Hungarian monarchy in 1918, there had been little coopera-
tion among these countries in macroseismological research. Ceci´ć believes
this was “the first known occasion that seismologists from several coun-
tries sat together and explained to everyone how the macroseismic studies
were organized at their institutes.”
4
One theme was the incongruity between
the data obtained from citizen-observers and the analytical methods of the
computer age. At one point, the Austrian representative admitted that, at his
institute, aggregate intensities and isoseismals were generally “determined
by experience.” “That is not objective enough,” responded an Italian col-
