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Abstract

The Alps formed during the African-European collision. Although the Alps are in the focus of geoscientific research over decades, its crustal and upper-mantle structure are still not completely known. The Periadriatic Lineament, a late orogonic fault active in Oligo-Miocene time, is sinistrally offset by the Guidicarie Fault. It is controversially discussed whether or not a switch in the subduction polarity on either side of the Guidicarie Fault can be observed. Our aim is to reveal the 3-D crustal structure of this section of the Alps at high-resolution by local earthquake tomography (LET). We use data of a temporary seismic network in the Southern and Eastern Alps (SWATH-D) which consists of 150 stations with an inter-station spacing of 15 km. The data from selected AlpArray (AASN) stations was included too. The first results of the inversion for hypocenters, velocity model, and station corrections are in a good agreement with the previous local and regional studies. However, our 1-D velocity model for this particular part of the Alps indicates upper-crustal velocities that are higher than the Alpine average. The seismicity pattern comprises diffuse clusters of earthquakes within the upper 25 km of the crust in the Friuli, Lake-Garda, Trentino and Brenner regions. The centre of the study region shows anomalously low seismic activity. This seismicity pattern indicates where ongoing Adria-Europe convergence is currently accommodated. A preliminary 3-D inversion shows satisfactory resolution and reveals the structure of the crust and uppermost mantle down to 50 km in most of the target area.