Characterisation of seismicity of the azores archipelago: an overview of historical events and a detailed analysis for the period 2000–2012

Abstract

The Azores Archipelago is located in the Middle Atlantic Ridge, at the Triple Junction formed by the contact of the Euro-Asiatic, the Nubia (African) and the American plates (see also Vogt and Jung, Chapter “ The “Azores Geosyndrome” and Plate Tectonics: Research History, Synthesis, and Unsolved Puzzles ”). Its seismicity rate is very high with earthquakes with relatively low magnitude, defining quite well the contact regions. This chapter gives an overview of the existing historical and instrumental catalogues, describes the seismicity of the region essentially since early 1915, and analyses in more detail the characteristics of the recorded data in the period 2000–2012. The spatial variations of the minimum magnitude of completeness (Mc) as well as the b-value is studied for this period within the stripe of observed seismicity which contains the alignment of the Archipelago islands. A preliminary interpretation of the Mc and b-values is made keeping in mind the geological transition between the Gloria fault to the East and the Mid-Atlantic Region to the West.