Estimation of the seismic hazard parameters for various sites in Greece using a probabilistic approach

International audienceThe probabilistic approach that was recently introduced by Kijko and Graham (1998,1999) was applied for the estimation of seismic hazard for various sites in Greece in terms of peak ground acceleration (PGA) and peak ground velocity (PGV). These sites represent geographically cities of Greece among which are the capital of Greece and some others with high, intermediate and low seismicity. The approach allows the use of earthquake catalogues with incomplete reported historical and complete instrumental data, the consideration of different magnitude thresholds, and the incorporation of magnitude uncertainties. One of the advantages of the method is that it does not require any determination of seismic zones. The estimated values of PGA for return periods of 476 years were grouped in 4 categories, the same ones used in the seismic hazard map for the New Seismic Code of Greece. Comparison results were quite interesting and very encouraging concerning the reliability of this probabilistic approach

Analysing Socio-Economic Change Using a Time Comparable Geodemographic Classification: England and Wales, 1991–2011

Geodemographic classifications are used to understand social phenomena. Within the private sector, for business planning accounting for underlying spatial differences in economic, social and demographic composition of geographical areas. In the public sector geodemographics is used in health, local governance and social research. Bespoke geodemographic systems help public health authorities to target neighbourhoods most at need of health campaigns. Geodemographic classifications are invariably cross-sectional and static. Having comparable geodemographic classifications over a period of time will help demonstrate changes in socio-economic and demographic structures. A time-comparable geodemographic scheme can bring out changes in multivariable compositional characteristics which are otherwise hidden by cross-sectional measures. This paper reports on variable selection, the conversion of inputs to a consistent geography and the creation of directly comparable geodemographic classifications of small areas across England and Wales for 1991, 2001 and 2011. Changes and stability in area characteristics are then analysed. The results show that most neighbourhoods are allocated into the same area type over time. Where there is change, this can be themed as: Socio-economic polarisation, characterised by a decrease in neighbourhoods found in the middle of the socio-economic spectrum, with an increase in number of areas at either end; Growth in the number of neighbourhoods with non-White ethnic residents, mainly Black ethnic minorities and Asian based communities and; Reorganisation and increase in classifications relating to urban areas, signalling development or growth of metropolitan areas