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 [...]

Tribal words for earthquake

In cases where the a study is being made of historical earthquakes in a low-seismicity and largely pre-literate area, one sometimes sees the argument made that the language of the local tribe has a word for earthquake, therefore they were familiar with the concept, therefore the area has been subject to earthquakes in the past.

Unfortunately, [...]

What's in a word? - Earthquake

The word “earthquake” is much the same in most languages. Take the word for “earth” and some word meaning “shaking”, and you have “erdbeben”, “tremblement de terre”, “terremoto”, “zemětřesení”, the list goes on. What is slightly curious is that in English the shaking word is “quake”, which is a less familiar term than “shake”. In [...]