Physical properties of Hradište border fault (Turiec Basin, Western Carpathians, Slovakia) inferred by multidisciplinary geophysical approach

The Hradiste border fault zone has played an important role in the development of the tectonic contact of the Cenozoic sediments of the Turiec Basin with the Mala Fatra Mountains crystalline basement. Seismic, geoelectric, radiometric, gravimetric, magnetometric and ground penetrating radar measurements were used to study the physical properties and determine the exact position and inclination of this fault zone down to a depth of up to 40 m. The Hradiste border fault zone represents an almost vertical physical boundary characterized by decreasing seismic velocity (from 3.0 km.s−1 to 2.2 km.s−1) and decreasing electrical resistivity (500 to 150 Ω.m) when passing from the basement west of the fault to sediments to its east. It corresponds also to a compact segment of the lowest volume activity of radon 222Rn values in soil air (8 kBq.m−3 on average) and maximum horizontal gravity gradient (−0.0076 mGal.m−1). The discovery of this anomalous zone also helps us to distinguish two different anomalous blocks. The block west of the fault represents the orthogneisses of the Tatric crystalline complex belonging to the Mala Fatra Mountains. The eastern block is built-up by the Bystricka Member Pliocene sediments of the Turiec Basin. Our study serves as a case study for geophysical research on faults in different tectonic units of the Western Carpathians and other similar orogens.