Seismological Network in Hungary: Insights from the AdriaArray Operational Period

Abstract

The Hungarian National Seismological Network has experienced significant advancements in its monitoring capabilities due to the increasing density of seismic stations across the country, leading to improved earthquake detection and localization. This paper presents an analysis of the noise characteristics, detection capabilities, and seismic events registered by the Hungarian National Seismological Network, utilizing data from both permanent and temporary stations, including those from international projects such as AlpArray, PACASE, and AdriaArray. The noise characteristics of the network were analyzed through probabilistic power spectral densities, highlighting the diverse noise conditions across Hungary. The stations were grouped based on their installation dates and geographical locations, revealing significant differences in noise levels due to geological conditions, anthropogenic influences, and seasonal variations. Noise conditions at high frequencies, crucial for detecting low‑magnitude local earthquakes, were particularly influenced by both geological factors and human activity. The study also investigated the horizontal‑to‑vertical spectral ratios and found correlations between sediment thickness, resonance frequencies, and noise levels at different stations. The paper assesses the detection capability of the seismic network, focusing on its ability to identify earthquakes of varying magnitudes. We estimated the maximum background noise displacement, providing insights into the detection thresholds of the network. The results showed that the network is capable of detecting events as small as magnitude ML = 0.5 during the night in northern Hungary and events larger than ML = 1.25 throughout the country during all day. A case study of the Szarvas cluster in 2023, a notable seismic swarm demonstrates the network’s ability to accurately localize earthquake sequences using advanced localization algorithms. This event highlighted the enhanced seismic monitoring capability of the expanded network and its ability to capture small local seismic events that were previously undetectable. The paper concludes with an overview of ongoing research and future developments, including studies on the crust and mantle structure of the Pannonian Basin and wider region, advancements in seismic hazard mapping, and the role of the AdriaArray stations in refining earthquake localization. The continuous development of the Hungarian National Seismological Network and its integration into international cooperations are expected to further enhance high quality seismological structural research and contribute to a more detailed understanding of regional seismicity