Hi All,

I see our friend Roger Musson will be an invited speaker at this years AGU Fall Session.

S12C-08 INVITED
TI: The Significance of Absent Earthquakes: What is the Weight of a Historian's Opinion?
AU: * Musson, R M
EM: r.musson@bgs.ac.uk
AF: British Geological Survey, West Mains Road, Edinburgh, EH9 3LA United Kingdom
AB: The level to which a historical earthquake catalogue is considered complete is one of the requirements of a seismic hazard analysis; seismic activity rates cannot be estimated from a catalogue alone without knowing about the completeness in terms of magnitude and date thresholds. A number of statistical tools have been proposed, and are sufficiently well known, that to some extent this subject is now viewed as routine. However, in areas of relatively low seismicity, statistical methods may be difficult or impossible to use, and completeness has to be judged using a historical assessment of source materials. The critical question becomes, "Given the state of historical writing for a given place and time, what is the magnitude threshold (if any) for which we can be certain that any earthquake above this threshold must have been recorded"? Answering this question in an objective way proves to be difficult. It is an extremely historical question, because any approach to it raises fundamental questions about the nature of the sources themselves. And yet it is also a rather practical question, since the answer may have a significant effect on the hazard value that a design engineer will ultimately have to work to. Experience shows that, all other things being equal, two different judgement calls by historians on the quality of source materials can change the final hazard value at a site by around 5 to 10 per cent. This is enough of a difference to make it worthwhile to devote some scrutiny to how these opinions are derived. In this study, the questions raised and the possible significance of the answers are explored in the context of the early seismicity of the British Isles.

Of course there are many other notables including Sue Hough, Roger Bilham and Topozada as well.

Petra