Palaeoseismic crisis in the Galera Fault (S Spain). Consequences in Bronze Age settlements?

Abstract

Abstract. Palaeoseismological studies play a crucial role in the seismic characterization of regions with slow moving faults. This is the case of the Central Betic Cordillera, a highly populated area where the record of prehistoric earthquakes is very scarce, despite of being one of the regions with the highest seismic hazard in Spain. We present here a palaeoseismological characterization of the Galera Fault, one of the active faults accommodating deformation in the Central Betic Cordillera. We excavated and analysed several trenches along the fault trace. We quantitatively correlate the results from these trenches, resulting in a surface rupture history involving 7 or 8 events (accounting for the epistemic uncertainties) during the last ca. 24000 yr, with a recurrence interval ranging between 1520 and 1720 yr. Further analysis of this surface rupture history seems to indicate that the Galera Fault is prone to produce earthquakes clusters, as we recorded five events in ca. 400 yr (ca. 1536–1126 BC), and only two events in the next ca. 3200 yr. Using the fault geometry and palaeoseismological data, we also carried out a seismogenic characterization of the fault. This analysis yielded a maximum expected magnitude of 6.7 ± 0.3 and a recurrence interval of 1857 yr. Furthermore, we also present a geodetic rupture scenario for the maximum expected event, involving displacements of up to 0.5 m. Finally, we discuss the possible impact of the deduced palaeoearthquakes in the development of Bronze Age human settlements located in the vicinity of the fault. Other than their intrinsic value, our results will be the basis for future seismic hazard assessment carried out in the Central Betic Cordillera.