Azimuth and slowness corrections in BURAR array estimated from regional events occurred in the Mediterranean area

Array processing techniques can characterize the details of arriving seismic waves front for different wave phases. We applied one of these techniques, f-k analysis, to estimate azimuth and slowness systematic deviations specific for Bucovina array (BURAR) and to detect significant lateral variations in the lithosphere structure. BURAR array is a high-quality monitoring system consisting of 10 elements located in the Northern part of Romania, in South-Eastern Carpathians. Data recorded by BURAR during 2004- 2007 time interval are collected from earthquakes located at regional distance and sufficiently large magnitude (higher than 4) to have an acceptable high signal/noise ratio. The distribution of the earthquakes shows strong inhomogeneous azimuth coverage: the majority of the earthquakes occurred in the Southern part relative to BURAR. Significant and systematic deviations in azimuth and slowness are emphasized. For comparison the same technique was applied in case of other two arrays, one located in Ukraine (AKASG) and the other one in Turkey (BRTR). The azimuth and slowness deviations are essential for estimating station corrections in order to improve the location quality. At the same time, they indicate the existence of significant lateral inhomogeneities in the lithosphere which can be interpreted in terms of the particular seismotectonics of the region crossed by seismic rays. (authors) Key words: seismic array, azimuth correction, slowness correction, f-k analysis