GEODYNAMICS

Abstract

The differential and source terms locations of a series of small (1.0<ML<2.5) similar (recurrent) earthquakes that occurred during 2013-2015 near the village of Trosnyk in the south of Transcarpathians were determined. Adaptive filtering was proposed to reduce the effect of correlated noise in records with very low signal-to-noise ratio and to improve the reliability of differential arrivals. The maximum correlation criterion was modified to include the minimum departure from the calculated arrival times. Analysis of the intervals between phase arrivals at pairs of stations was proposed to further reduce the number of problematic arrivals. The sensitivity of the final solution to the network configuration was assessed using the jack-knife principle, when the coordinates are calculated, each time removing one station from the full set. The focal mechanism common to all earthquakes in the series was defined using the polarities of P-wave arrivals at 16 stations. Based on the results of the 3D interpretation of the differential hypocenters, the nodal plane with a strike of 150° was identified as the rupture plane, and the mechanism itself was classified as left-lateral slip with a component of thrust. The epicenter of the strongest earthquake was located almost exactly on the fault of the pre-Neogene basement with a strike parallel to the Carpathian arc, almost the same as the strike of the rupture plane. The axis of compression in the focal mechanism is directed to the east, which is fully consistent with the northeast direction of the general regional field.