The latest on L’Aquila

I have had a number of messages from various people in the scientific community in the UK asking if there is any petition they can sign in support of the Italian scientists recently convicted of involuntary manslaughter over the affair of the L’Aquila earthquake. While I’m not aware of any petition, I do know that [...]

Probabilistic programming

Given the importance of probability to modern seismic hazard assessment, I found it interesting to discover the other day the world’s only probabilistic programming language. It’s called Java2K and was invented by Gerson Kurz. As the name suggests, it’s sort of an update on the Java programming language, with which it shares some features. However, [...]

A new approach to seismic risk

One of the problems with handling seismic risk for the broader community (public, politicians, etc) is that those who do the calculations (the seismologists) tend to speak a different language from those who are supposed to be receiving the benefit. In particular, seismologists handle risk (a) numerically, and (b) probabilistically. This is fine for the [...]

Safety valves

The fullest account of the impending prosecution over the L’Aquila quake that I’ve seen so far is on the Nature web site.

Most of the web traffic that I’ve seen has been strongly supportive of the seismologists in the case, though one issue that has been raised is whether it was said by anyone that “there [...]


There is, of course, another problem with “ground motion prediction equations”, which is that it’s such a mouthful. Which leads some people to condense it into the horrible “gumpy”. I was at a meeting last week where one presenter kept talking about “selecting the gumpies” and “arranging the gumpies”, much to the bafflement of about [...]


Whatever happened to attenuation? From the 1970s onwards, the word was used to refer to that part of the seismic hazard analysis that described the relationship between ground motion at site and an earthquake at distance. It was certainly current in the mid 2000s, to judge from the “Next Generation Attenuation” or NGA project. But [...]

Hazard values

The definition of seismic hazard in the previous post can actually be written two different ways:

Hazard is the probability that a certain strength of earthquake shaking will occur at a place.
Hazard is the strength of shaking that has a certain probability of occurring at a place.

Obviously, one is just the inverse of the other. However, [...]


To most people outside the seismological or earthquake engineering communities, the terms “seismic hazard” and “seismic risk” (or “earthquake hazard/risk”) probably seem interchangable. But within the profession, they have distinct meanings, and woe betide if they get misused. Specifically:

Hazard is the probability that a certain strength of earthquake shaking will occur at a place.
Vulnerability is [...]