Sismicidad y sismotectónica en Uruguay.

Abstract

The seismicity in the Uruguayan territory which is situated in the South American intraplate region is studied taking into account the tectonie and geophysical data gathered mainly in the last two decades, and the researchs in the topic fostered by projects comprising the whole Continent. Also several earthquakes focused in the region in 1848, 1888, 1988 and 1990 are reported. The primary result of such investigations has been to set a clear-cut differentiation in the seismic risk levels between the continental and marine zones of the country. In the first one a current tectonic stability has been found which, in tum, arises for a minimal seismic inland activity. However, in the second zone --referred to as the Rio de la Plata Region-- took place the formation of a tectonic basin related with the opening of the Atlantic Ocean in an aulacogenical way. This process that involves expansion of deep materials from asthenospherical levels has been responsible for stresses in a crust with píastic flow in its lower part and with block faulting and subsidence in its brittle upper part. That depth-dependent rheology added to the local sedimentary evolution and its present stress state, allows to infer the existence of at least one seismic province in the eastern part of the Rio de la Plata Region, namely the Punta del Este Basin where sources of other tectonic earthquakes might be located in the future.