The recent (upper Miocene to Quaternary) and present tectonic stress distributions in the Iberian Peninsula

A general synthesis of the recent and present stress situation and evolutio n in the Iberian Peninsula was obtained From microstructural and seismologi cal analysis. The stress evolution was deduced from (1) fault population an alysis (FPA) from 409 sites distributed throughout the Iberian Peninsula, ( 2) paleostress indicators given by 324 stations taken from the bibliography , and (3) seismic data corresponding to 161 focal mechanisms evenly spread in the studied region. The application of FPA together with the determinati on of stress tensors and focal mechanisms for the whole Iberian microplate has provided two main results: (1) the Iberian Peninsula is undergoing a NW -SE oriented compression, except for the northeastern part (Pyrenees, Ebro Basin, and Iberian Chain), where it is N-S to NE-SW, and the Gulf of Cadiz, where it seems to be E-W, and (2) the main trends of the stress field have remained almost constant since the upper Miocene. The analysis performed b y zones suggests the presence of local heterogeneities in the stress field.