The seismicity of Portugal and its adjacent Atlantic region from 1300 to 2014: Maximum Observed Intensity map (MOI)

In this study, we considered earthquakes with a maximum observed intensity (MOI) Io≥V that occurred throughout the Portuguese mainland and its adjacent Atlantic region to produce the map of maximum intensities of Portugal. This map is based on a wide variety of historical and recent sources, including 175 earthquakes, over the period of 1300–2014. This MOI map allows the regions of high, medium, and low levels of seismic hazard to be highlighted. The entirety of Portugal has been affected by major seismic events, some of which have caused serious damage. In addition, offshore earthquakes have had significant impacts on the coastal cities located in the central and southern regions of the country. Because the southern region of mainland Portugal is more active than the northern region, the largest concentrations of events with Io≥VI are in the southern region, especially on the mainland near the city of Évora, in the Lisbon region, in the Lower Tagus Valley region, and along the Algarve coast, especially in the southwest region in Cape of São Vicente and the Gorringe Bank.

Lithosphere Thickness, Heat Flow and Moho Depth in the South of Portugal

Abstract In the last years, several models have been presented trying to obtain lithosphere and Moho thickness in the Iberian Peninsula, using data related to geoid elevation and topography, gravity, seismicity and thermal analysis. The results obtained show a decrease in the thickness of the crust and the lithosphere in the SW part of the Iberian Peninsula. Density anomalies in the crust are also referred. Data obtained in the region was collected and deviations from average values used were detected. In this work, models were made taking into account the specific characteristics of the region. Heat flow, thermal conductivity, heat production, topography, gravity, seismic and geological data available for the region, were used to adjust the model. The results show that this region is different from other parts of the Iberian Peninsula and a special attention must be given to it. This work shows the importance of trying to know and understand the thermal structure of the region.

Lithosphere Thickness, Heat Flow and Moho Depth in the South of Portugal

ABSTRACT In the last years, several models were presented trying to obtain lithosphere and Moho thickness in the Iberian Peninsula, using data related to geoid elevation and topography, gravity, seismicity and thermal analysis. The results obtained show a decrease in the thickness of the crust and the lithosphere in the SW part of the Iberian Peninsula. Density anomalies in the crust are also referred. The work I intend to present is related with the south of the Ossa Morena Zone, the South Portuguese Zone and the Algarve, in the south of Portugal. Data obtained in the region was collected and deviations from average values used were detected. Models were made taking into account the specific characteristics of the region. Heat flow, thermal conductivity, heat production, topography, gravity, seismic and geological data available for the region, are used to adapt the models. A special attention will be given to the spatial variation of heat flow values and to Moho depth in the region. The results show that this region is different from other parts of the Iberian Peninsula and a special attention must be given to it. The different values obtained using seismic, gravity, and geoid height data, and the results obtained with models using thermal data shows the importance of trying to know and understand the thermal structure of the regions. Problems related with the use of average values will be focused.

Azores seismogenic zones

One condition to perform seismic hazard analysis is knowledge about seismogenic zones that is an invaluable source of information and play an important role because it is fundamental know the processes and properties that control the seismogenic zone. The aim of this work is distinguishing seismogenic zones in the Azores region applying different parameters such as the earthquake density, b-values, focal mechanism, historical seismicity and all of these conjugated within the geodynamic framework of the Azores. We identified 10 seismogenic zones plus the well known Mid Atlantic Ridge. The 10 zones we identified are over the major tectonic structures of the Archipelago, namely Terceira Rift and Linear Volcanic Ridges.