Structure of the Lithosphere Beneath Macedonia From Teleseismic Receiver Functions

The Republic of Macedonia is situated in the Balkan region of Southeast Europe. This region is one of the most tectonically and seismically active areas on the continent, and consequently, characterized by a very high seismic hazard and risk. The Seismological Observatory Republic of Macedonia (SORM) network consists of five permanent and a number of temporary stations. Three of these stations have been in service since the late 1950’s and 1960’s and are geographically spread across the country. Although there is an established seismological network in Macedonia, until the present there has been a very limited study of the SORM data using teleseismic receiver functions. In determining regional and European-wide models such studies must be undertaken in areas that have not been studied yet to provide more accurate results and easier interpretation of the Earth’s structure and dynamics. There are indications from previous deep seismic sounding studies of Macedonia and former Yugoslavia that there is a major tectonic change in the west and that the crust significantly thickens towards west, but a uniform one-dimensional horizontally layered model is still in a routine seismological practice use in Macedonia. We computed teleseismic P wave radial and transverse receiver functions from three-component seismograms of selected teleseismic earthquakes recorded at VAY (Valandovo, east Macedonia), SKO (Skopje, north Macedonia) and OHR (Ohrid, southwest Macedonia) seismological stations. We used a multi-step procedure with a rigorous statistical approach to determine the observed receiver function-averages at individual stations and a grid search to invert for models of a simple crustal structure. These models were then used as starting models for more detailed modeling that is a combination of a linearized inversion and an interactive forward modeling. The preliminary results for VAY point to the Moho depth of about 34 km, which is in agreement with previous studies in the neighboring countries. In addition, VTS (Vitosha) station from Bulgaria with a long continuous record of teleseismic data has been used in our study to provide the continuity of lithospheric profiles with other regions, and the comparison with previous results. This presents an excellent opportunity to include a missing piece of a puzzle for a country whose area has mostly been excluded from the regional scale interpretations of south-eastern Europe and the Balkan region.