Hazard Evaluation in Valparaiso: the MAR VASTO Project

The Project MAR VASTO (Risk Management in Valparaiso/Manejo de Riesgos en Valparaiso), funded by BID/IADB (Banco InterAmericano de Desarrollo/InterAmerican Development Bank), has been managed by ENEA, with an Italian/Chilean joined partnership and the support of local institutions. Valparaiso tells the never-ending story of a tight interaction between society and environment and the city has been declared a Patrimony of Humanity by UNESCO since 2003. The main goals of the project have been to evaluate in the Valparaiso urban area the impact of main hazards (earthquake, tsunami, fire, and landslide), defining scenarios and maps on a geo-referenced GIS database. In particular, for earthquake hazard assessment the realistic modelling of ground motion is a very important base of knowledge for the preparation of groundshaking scenarios which serve as a valid and economic tool to be fruitfully used by civil engineers, supplying a particularly powerful tool for the prevention aspects of Civil Defense. When numerical modelling is successfully compared with records (as in the case of the Valparaiso, 1985 earthquake), the resulting synthetic seismograms permit the generation of groundshaking maps, based upon a set of possible scenario earthquakes. Where no recordings are available for the scenario event, synthetic signals can be used to estimate ground motion without having to wait for a strong earthquake to occur (pre-disaster microzonation). For the tsunami hazard, the available reports, [e.g., SHOA (1999) Carta de Inundacion por Tsunami para la bahia de Valparaiso, Chile, http://www.shoa.cl/servicios/citsu/citsu.php], have been used as the reference documents for the hazard assessment for the Valparaiso site. The deep and detailed studies already carried out by SHOA have been complemented with (a) sets of parametric studies of the tsunamigenic potential of the 1985 and 1906 scenario earthquakes; and (b) analytical modelling of tsunami waveforms for different scenarios, in order to provide a complementary dataset to be used for the tsunami hazard assessment at Valparaiso. In addition, other targeted activities have been carried out, such as architectonic/urban planning studies/vulnerability evaluation for a pilot building stock in a historic area and a vulnerability analysis for three monumental churches. In this paper, a general description of the work is given, taking into account the in situ work that drove the suggestion of guidelines for mitigation actions.