Programa de Doutoramento em Ciências da Terra e do Espaço
Seismicity and Seismic Hazard Assessment in the Azores
João Fontiela

Orientação:  Mourad Bezzeghoud, Philippe Rosset & Francisco Cota Rodrigues

The peculiar geodynamic framework of the Azores is responsible by the high number of events of low magnitude, despite several earthquakes of M≥5 or maximum intensity ≥VII that in the past affected the islands of the Central and Eastern groups. Thus, the seismic hazard is considerable and the study of the seismicity is a challenge to the scientific community.
This thesis, which comprises four papers published and one submitted, is a comprehensive study of the seismicity and seismic hazard in the Azores.
The analysis of the seismicity using b-value of frequency-magnitude distribution reveals a general decrease trend from west to east. The high b-values could be within the volcanic activity, thermal anomalies or hydrothermal activity while the low b-values are certainly related with the increase of effective stress. In the scope of the seismic hazard assessment we identify 11 seismogenic zones where the b-values ranges from 1.57 in the Middle Atlantic Ridge to 0.72 in the seismogenic zone of Terceira Island. We select maximum observed intensity (MOI) maps to assess the maximum ground shaking using historical and instrumental seismicity since this analysis is performed with MOI. Still, in the seismic hazard, we estimate human losses caused by possible earthquakes in the future on a volcanic island, although the difficulties inherent to the geological heterogeneities. The last two topics (MOI maps and human losses) were a pioneer work since they were applied for the first time in the Azores, therefore contributing to mitigate the seismic hazard in the Azores region.

Keywords: Seismicity, Seismic hazard, Seismogenic zones, Maximum observed intensity, Human losses estimation