Eurocode 8 seismic hazard zoning maps for the UK

Abstract

The earliest attempt to map seismic activity, and hence hazard, in the UK was made by O’Reilly
\n(1884), and the (perhaps better known) map of Ballore (1896) does show a division of the British
\nIsles into distinct zones. However, at this early date, hazard could only be expressed in terms of
\nsimple distinctions between levels of frequency of earthquake occurrence, usually subjectively
\nassessed, and not as ground motion, which is how seismic hazard is expressed today.
\nThe first true hazard map (in the modern understanding of the word) for Great Britain was thus
\nthat of Lilwall (1976), which expressed hazard in terms of intensity with a 200-year return
\nperiod, using an extreme-value technique based on the work of Milne and Davenport (1969). A
\nsubsequent study by Ove Arup (1993) used true probabilistic seismic hazard assessment (PSHA)
\nto calculate hazard at selected points in the UK, but these points were too few to be contoured.
\nThe first contour maps of hazard on the UK territory produced using PSHA were therefore those
\nof Musson and Winter (1996), prepared for the then Department of Trade and Industry (DTI).
\nThe UK was, of course, also covered in two major international seismic hazard mapping
\nprojects, the Global Seismic Hazard Assessment Programme (GSHAP) and SESAME (Grünthal
\net al 1996, Jiménez et al 2001). Both these studies used a common source model for the UK,
\nwhich was derived from a simplified version of the Musson and Winter (1996) model. The
\nresults are in conformity with those of Musson and Winter (1996), although different ground
\nmotion models were used.
\nAn updated hazard map for the UK was published by Jackson (2004), but only for intensity. This
\nis described in Musson (2004a).
\nA specific zoning map for the UK was produced for a report on dam safety for the UK, and has
\nsince been widely circulated (Halcrow 1990). This map assesses hazard in a completely
\nsubjective way into high, medium and low classes, which are to be understood as entirely
\nrelative terms. Despite its informal nature, it proved to be a reasonable depiction of relative
\nhazard levels when compared to later quantitative maps.