Evidence for past earthquakes in an area of low historical seismicity: the Catalan coastal ranges, NE Spain

E. Masana

Abstract


The Catalan coastal ranges are situated far away from a plate margin and thus are characterised by low rates of deformation and low seismicity. Nevertheless, up to six morphological scarps in quaternary alluvial fans, large landslides and liquefaction features were detected in the southern half of these ranges and motivated a more detailed geomorphologic and palaeoseismologic study. In the Baix Ebre Fault zone, the morphological analysis of the mountain front and the fluvial network showed evidence of alternative periods of uplift and quiescence and suggested a sub-actual reactivation of the fault after a recent stable period. In El Camp zone the Almadrava andMont-roig scarps were analysed in detail. The first shows evidence of fault control and of two probably seismic deformation events. A normal semi-hidden fault that folds the surface was suggested to explain the deformation observed in this scarp. The second is also considered to be controlled by a fault which was active between 100000 and 4490-4790 year B.C. If creep deformation could be rejected the Mont-roig scarp fault may be considered an active fault able to generate large earthquakes (M > 6.5). In summary, although the zone shows low historical seismicity, evidence that can be referred to past earthquakes was detected. Further palaeoseismologic studies should be carried out in these structures in order to better constrain the active behaviour of the faults.

Keywords


fault scarps;geomorphology;Quaternary;palaeoseismicity;Catalan coastal ranges

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References


DOI: https://doi.org/10.4401/ag-4000
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Published by INGV, Istituto Nazionale di Geofisica e Vulcanologia - ISSN: 2037-416X