Mualchin said that seismic hazards were not properly assessed in L’Aquila. "Italy is one of the countries with the best seismic knowledge in the world. And yet look at what a 6.3 earthquake has done to this city. That knowledge was not used, and scientists are responsible for that. They were conscious of the high risk in the area, and yet did not advise the people to take any precaution whatsoever,” he said.
The problem is in part a scientific one, Mualchin said. The Italian scientists based their analysis on the frequency of earthquakes in the area. This is known as the probabilistic seismic-hazard analysis (PSHA), a method that is state of the art in many countries, but that, in Mualchin’s view, systematically underestimates seismic hazard because it does not consider extreme and rare events.
"Frequency is not important, what really matters is the largest earthquake we can expect, the strongest one that has happened in the past. Risk prevention should be based on that,” he said. This is the philosophy behind deterministic seismic-hazard analysis, a method that Mualchin says has been mostly abandoned by the scientific community, to the point that younger seismologists do not even learn about it.
"PSHA is a bad model California has exported elsewhere, and we see the results here in L’Aquila," he told Nature after the hearing. Mualchin worries that the new building codes approved in Italy after the L’Aquila earthquake show no improvement. "They never consider the worst-case scenario for any particular area, and this can lead to new disasters in the future”.
This article is reproduced with permission from the magazine Nature. The article was first published on February 16, 2012.