Abstract
Abstract. The objective of this paper is to define seismic zones in the Azores based on statistical criteria. These seismic zones will likely be used in seismic simulations of occurrences in the Azores Archipelago. The data used in this work cover the time period from 1915 to 2011. The Azores region was divided into 1° × 1° area units, for which the seismicity and the maximum magnitudes of events were calculated. The seismicity, the largest earthquakes recorded and the geological characteristics of the region were used to group these area units because similar seismic zones must delineate areas with homogeneous seismic characteristics. We have identified seven seismic zones. To verify that the defined areas differ statistically, we considered the following dissimilarity measures (variables): time, size and seismic conditions – the number of seismic events with specific characteristics. Statistical tests, particularly goodness-of-fit tests, allowed us to conclude that, considering these three variables, the seven earthquake zones defined here are statistically distinct.
Highlights
IntroductionThe Azores Archipelago is located at the triple junction of the Mid-Atlantic Rift, where the Eurasian, Nubian, and American Plates meet.The intense seismic activity in the region has been studied by many authors (e.g., Bezzeghoud et al, 2008; Borges et al, 2008).As shown in Fig. 1a, the Azores consists of nine islands distributed among three different groups: the islands of Flores and Corvo, constituting the Western Group; the islands of Terceira, Graciosa, São Jorge, Faial and Pico, which are part of the Central Group; and the islands of São Miguel and Santa Maria in the Eastern Group.Figure 1b shows epicenters in the Azores between 1915 and 2011, and Fig. 1c shows a zoomed-in map of epicenters of the islands.The aim of this study is to define the seismic zones of the Azores, which will later be used for seismic simulations of the region.We define several zones that express differences in seismicity, while allowing for a model that is not overly complex
To verify that the defined areas differ statistically, we considered the following dissimilarity measures: time, size and seismic conditions – the number of seismic events with specific characteristics
The aim of this study is to define the seismic zones of the Azores, which will later be used for seismic simulations of the region
Summary
The Azores Archipelago is located at the triple junction of the Mid-Atlantic Rift, where the Eurasian, Nubian, and American Plates meet.The intense seismic activity in the region has been studied by many authors (e.g., Bezzeghoud et al, 2008; Borges et al, 2008).As shown in Fig. 1a, the Azores consists of nine islands distributed among three different groups: the islands of Flores and Corvo, constituting the Western Group; the islands of Terceira, Graciosa, São Jorge, Faial and Pico, which are part of the Central Group; and the islands of São Miguel and Santa Maria in the Eastern Group.Figure 1b shows epicenters in the Azores between 1915 and 2011, and Fig. 1c shows a zoomed-in map of epicenters of the islands.The aim of this study is to define the seismic zones of the Azores, which will later be used for seismic simulations of the region.We define several zones that express differences in seismicity, while allowing for a model that is not overly complex. The intense seismic activity in the region has been studied by many authors (e.g., Bezzeghoud et al, 2008; Borges et al, 2008). The aim of this study is to define the seismic zones of the Azores, which will later be used for seismic simulations of the region. We define several zones that express differences in seismicity, while allowing for a model that is not overly complex. Seismic zones are defined by polygons that delineate areas of homogeneous seismicity characteristics. They are based on differences in geology and tectonics, but seismicity is the main characteristic in defining them (e.g., Reiter, 1991; Kagan et al, 2010)
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