Ore prospecting using gravimetric and magnetic data has become one of the traditional approaches in the last decades, often complemented with electric and electromagnetic methods. However, due to the problem of non-uniqueness inherent to potential-filed modelling, constrains provided by structural methods such as seismic reflection are often used. During the exploration of massive sulphide polimetallic minerals in the Iberian Pyrite Belt Figueira de Cavaleiros sector, located in the Sado Tertiary Basin, several gravimetric and magnetic anomalies were considered as interesting targets. In order to reduce ambiguity of the gravimetric modelling and to confirm the geological model of the area, two seismic reflection profiles were acquired. The interpretation of these profiles was assisted by three mechanical boreholes, two of them located in the research area, in order to make a seismostratigraphic interpretation. Unfortunately, the gravimetric modelling suggests that the anomaly has a lithological and structural origin and is not related with massive sulphides. Nevertheless, a good agreement between the seismic and potential-field data was achieved and new insights into the geological model for the region were obtained form this work, with accurate data about the Tertiary cover and Palaeozoic basement.

The Algarve province of Portugal is located near the E-W Eurasia-Africa plate boundary. It is characterized by a moderate seismicity, with some important historical earthquakes causing important damage and economical losses. Not only has it suffered the effects of large plate boundary events but also the impact of local onshore moderate-sized earthquake sources. The seismic hazard evaluation and mitigation of the area is therefore of great importance to the local populations and the large number of tourists that frequent the region. This paper focuses the evaluation of the most interesting and useful geotechnical near-surface parameters and a soil classification. The classification based upon the European Code 8 for civil engineering and SPT bedrock data, was carried out for land use planning and design of critical facilities. P-wave and S-wave seismic velocities were obtained through the acquisition, processing and interpretation refraction profiles. Hundreds of SPT parameters from available boreholes drilled for engineering and water supply were used and subsoil classification based on geophysical and geotechnical parameters is presented. Other parameters, such as Vp/Vs ratios and the Poisson coefficient were estimated and were computed to provide information for future site effect studies. The experimental procedure tested here is relatively fast, economical and easy to perform and can be useful to estimate soil microzoning and seismic hazard mapping in the absence of local earthquake records.