The Role Of Small-Scale Fold And Fault Development In Seismogenic Zones: Example Of The Western Huercal-Overa Basin (Eastern Betic Cordillera, Spain)

The NW-SE shortening between the African and the Eurasian plates is accommodated in the eastern Betic Cordillera along a broad area that includes large N-vergent folds and kilometric NE-SW sinistral faults with related seismicity. We have selected the best exposed small-scale tectonic structures located in the western Huercal-Overa Basin (Betic Cordillera) to discuss the seismotectonic implications Of Such structures usually developed in seismogenic zones. Subvertical ESE-WNW pure dextral faults and E-W to ENE-ESW dextral-reverse faults and folds deform the Quaternary sediments. The La Molata structure is the most impressive example, including dextral ESE-WNW Neogene faults, active southward-dipping reverse faults and associated ENE-WSW folds. A molar M1 assigned to Mimomys savini allows for precise dating of the folded sediments (0.95-0.83 Ma). Strain rates calculated across this structure give similar to 0.006 mm a(-1) horizontal shortening from the Middle Pleistocene Up until now. The widespread active deformations on small-scale structures contribute to elastic energy dissipation around the large seismogenic zones of the eastern Betics, decreasing the seismic hazard of major fault zones. Copyright (C) 2009 John Wiley & Sons, Ltd.