Analysis of the efficiency and seasonal performance of the Azores infrasound experimental arrays

The infrasound monitoring network in the Azores currently comprises the International Monitoring System (IMS) station IS42 on Graciosa Island, together with two small-aperture (140 m) experimental arrays (SJ1 and TER) deployed on São Jorge and Terceira Islands. This network enables a more comprehensive coverage of the region, improving the detection of seismo-volcanic activity and the characterisation of atmospheric phenomena such as storms and fireballs. In this work, we present a statistical analysis of one year of infrasound detections, focusing on the identification of persistent sources and the assessment of noise level variability. In addition to continuous background activity, the network successfully recorded signals associated with local earthquakes, storms, and aeroplanes. The results showed consistent directional patterns and clear diurnal cycles, with enhanced daytime detections likely related to anthropogenic activity. The study demonstrates the strong performance of the experimental arrays, which provide reliable and complementary observations to IMS station. Also, it highlights the importance of further strengthening the regional infrasound network to improve the understanding of volcanic systems and their behaviour. Therefore, the deployment of additional arrays is recommended to increase spatial coverage, source discrimination, and improved monitoring capability in the Azores.