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Abstract

This work details the variations in heat flow density and thermal properties of rocks in five 300–450 m deep fully cored boreholes in the seismically active part of the West Bohemia at the border of Czechia and Germany. All the boreholes were drilled in the crystalline units, with boreholes S1 (Landwüst, 50.26°N, 12.33°E), S2 (Tisová, 50.35 °N, 12.50 °E) and S3 (Studenec, 50.26 °N, 12.52) intersecting metamorphic rocks, borehole S4 (Bažina, 50.15°N, 12.21°E) passing through the sedimentary cover of a newly discovered maar and the underlying granite, and borehole PTP-3 (Potůčky, 50.43 °N, 12.78 °E) completely drilled in granite. Precise repeated temperature logging was performed for all the boreholes, and due to the hilly terrain, topographic corrections were applied using 3-D numerical models to account for the effects of topography on the borehole temperatures. Thermal properties, including their anisotropy, were determined in the laboratory on ten or more rock samples from each borehole. Hence, it was possible to analyze depth variations of the heat flow in the individual boreholes. The largest variations occur in the boreholes located in metamorphic rocks. Due to rock heterogeneity, anisotropy of thermal properties, effect of climate change and water movement, the heat flow density ranges from less than 50 mW m⁻² to more than 100 mW m⁻². The research is supported by the Czech Science Foundation, project no. 21-23196S.