Geophysical identification of geo-morphologically indistinctive Miocene maar-diatreme volcanoes in Western Bohemia and their seismic amplification effect

This study uses ambient seismic noise processing methods as the primary tool to investigate suspected maar volcanic structures at Nežichov village and Sepuska hill in West Bohemia, Czechia. The research employs ambient seismic noise surveys, gravimetric surveys, electrical resistivity tomography (ERT), and numerical modeling to analyze these structures. At Nežichov, the ambient seismic noise survey identified fundamental mode amplification frequencies, with particle motion trends indicating a complex 3D resonance structure. The gravimetric survey revealed a negative anomaly, suggesting a volcanic breccia fill. ERT results showed low resistivity zones attributed to maar lake sediments, with a high resistivity intrusion dividing these zones. At Sepuska, similar methods identified fundamental mode frequencies, with a circular amplification distribution. The gravimetric survey indicated a negative anomaly, consistent with a maar structure. The study concludes that both Nežichov and Sepuska are likely maar volcanic structures, with complex subsurface features revealed through combined geophysical methods. These findings contribute to understanding the volcanic history and geological evolution of the Bohemian Massif.