Surface and subsurface Palaeoseismic records at the ancient Roman City of Baelo Claudia and the Bolonia Bay area, Cádiz (south Spain)
Pablo G. Silva, Klaus Reicherter, Christoph Grützner, Teresa Bardají, Javier Lario, Jose L. Goy, Cari Zazo, Peter Becker-Heidmann, 2009. "Surface and subsurface Palaeoseismic records at the ancient Roman City of Baelo Claudia and the Bolonia Bay area, Cádiz (south Spain)", Palaeoseismology: Historical and Prehistorical Records of Earthquake Ground Effects for Seismic Hazard Assessment, K. Reicherter, A. M. Michetti, P. G. Silva
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The Roman archaeological site of Baelo Claudia (Cádiz, south Spain) is located within the Gibraltar Arch, a region with no significant recent or historical seismicity. However, previous studies have emphasized the occurrence of repeated strong archaeoseismic damage (intensity≥IX MSK) at Baelo Claudia tentatively bracketed in this study around ad 40–60 and ad 260–290. A multidisciplinary study has been carried out including the detailed mapping of surface deformation and building damage, surface geology and geomorphology, collection of structural data, and an extensive ground penetrating radar (GPR) survey. The obtained data are not conclusive when considered separately, but evident links between archaeoseismic damage, structural and GPR data indicate that the destruction of the city was linked to seismic shaking. The analysis of the pattern and orientation of deformation clearly indicates SW–NE directed compression due to ground shaking. This analysis also focuses on localized landslides and liquefaction processes, which appear to be coeval with the earthquakes, but the poor geotechnical parameters of the clayey substratum were determinant to amplify the observed level of destruction. The application of the present Spanish seismic code (NCSE-02) indicates that intensity VIII MSK (0.24–0.26 g) can be reached in this zone for 500 year return periods.
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Palaeoseismology: Historical and Prehistorical Records of Earthquake Ground Effects for Seismic Hazard Assessment
Given the tremendous toll in human lives and attendant economic losses, it is appropriate that scientists are working hard to understand better earthquakes, with the aim of forecasting and, ultimately, predicting them.
In the last decades increasing attention has been paid to the coseismic effects on the natural environment, creating a solid base of empirical data for the estimation of source parameters of strong earthquakes based on geological observations. The recently introduced INQUA scale (Environmental Seismic Intensity–ESI 2007 Scale) of macroseismic intensity clearly shows how the systematic study of earthquake surface faulting, coseismic liquefaction, tsunami deposits and other primary and secondary ground effects can be integrated with “traditional” seismological and tectonic information to provide a better understanding of the seismicity level of an area and the associated hazards. At the moment this is the only scientific means of equating the seismic records to the seismic cycle time-spans extending the seismic catalogues even to tens of thousands of years, improving future seismic hazard analyses.
This Special Publication covers some of the latest multidisciplinary work undertaken to achieve that aim. Eighteen papers from research groups from all continents address a wide range of topics related both to palaeoseismological studies and assessment of macroseismic intensity based only on the natural phenomena associated with an earthquake.