Tsunami deposits in the western Mediterranean: remains of the 1522 Almerı́a earthquake?
Klaus Reicherter, Peter Becker-Heidmann, 2009. "Tsunami deposits in the western Mediterranean: remains of the 1522 Almerı́a earthquake?", 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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Shallow drilling in the lagoon of the Cabo de Gata area proved sedimentary evidence for a palaeo-tsunami along that part of the Spanish Mediterranean coast. Several coarse-grained intervals form fining-up and thinning-up sequences that are interpreted as tsunamites. Inland-extending sand sheets are used to identify tsunamigenic inundations. Other indicative features found are erosive bases, rip-up clasts, broken shells of bivalves and benthic/planktic foraminifera. The coarse-grained intervals consist of up to three sequences separated from each other by a silty mud drape. These intervals are interpreted as deposits of a tsunami train and correspond to three individual waves. Radiocarbon dating reveals evidence that these layers can be ascribed to deposition during the 1522 Almerı́a earthquake.
The 1522 Almerı́a earthquake (M>6.5) affected large areas in the western Mediterranean and caused more than 1000 casualties. The epicentral area was offshore in the Gulf of Almerı́a (southern Spain) along the Carboneras Fault Zone and seismic shaking triggered submarine slides in the Gulf of Almerı́a, which may have caused tsunami waves.
We have also found another intercalation of tsunamites downhole, which are interpreted as either an expression of repeated earthquake activity or tsunami-like waves induced by submarine slides triggered by seismic shaking in the Gulf of Almerı́a. Our evidence suggests a definite tsunami potential and hazard for offshore active and seismogenic faults in the western Mediterranean region.
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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.