Focal depths of earthquakes in the Carpathian Basin

Abstract

Analysing the areal distribution of earthquakes produced in the Carpathian Basin the conclusion can be drawn that only certain parts can be considered active along fracture lines, namely those parts which separate individually moving blocks. Generally accepted working theory states that if one fracture line ever generated an M-magnitude earthquake then at any point of the same line a similar or larger tremor may happen again. However, this principle is not supported by domestic experiences. In accordance with focal depths analysis we are going to verify that earthquakes were produced within more or less consolidated layers inside subsiding basins. Our analysis is aimed to explain the possible origin of earthquakes within small depth range and to point out the practical benefit of these investigations. We present also an analysis on the possible origin of „basin tremors” not taken so far into consideration and we offer a plausible explanation. Uncertainties of focal depth (hypocenter) determinations will also be given and we define relations between the focal depth (h), the magnitude (M), and the epicentral intensity (Io). The result will be presented in tables and comparison will be given between the focal depth data determined by us and by others. Finally viewpoints will be presented to help the recognition of earthquake foci and to set earthquake hazard determination on a real basis.