Public response to two rare earthquakes: crowdsourcing constraints on crustal structure in south Bohemian Massif

We analysed two rare earthquakes that occurred near Mirotice in south Bohemian Massif (Czechia) in March 2024 (ML 3.5) and April 2025 (ML 3.1), integrating seismological analyses with crowdsourced macroseismic observations. Both events originated at unusually large depths for the region (24.5 km) and were widely felt across southern and central Bohemia, attracting significant public attention. Independent of low population density, macroseismic effects were documented through extensive citizen participation, with over 1500 questionnaires for each event collected by the Institute of Geophysics, Czech Academy of Sciences. Maximum macroseismic intensities reached IV; however, the spatial distribution of observations was distinctly non-circular, forming a pattern controlled by major tectonic structures. Areas underlain by granitoids of the Central Bohemian Pluton exhibited dense and far-reaching macroseismic responses, consistent with low seismic energy attenuation of the Moldanubian, whereas regions dominated by early Palaeozoic sedimentary rocks of the Teplá–Barrandian showed sparse observations, indicating higher attenuation. The results indicate that crowdsourced data can constrain deep geological structures and effectively complement instrumental observations in regions with sparse seismicity.