B\uf6hm, Gualtiero

Colavitti, Leonardo

Costa, Giovanni

Gallo, Antonella

Tiberi, Lara

COLAVITTI, LEONARDO

TIBERI, LARA

COSTA, GIOVANNI

GALLO, ANTONELLA

Böhm, Gualtiero

Archivio istituzionale della ricerca - Università di Trieste

ESC2016-109, 201635th General Assembly of the European Seismological Commission© Author(s) 2016. CC Attribution 3.0 License.Local earthquake tomography in the junction domain betweenSoutheastern Alps and Dinarides using the seismic data of the CE3RNLeonardo Colavitti (1,2), Lara Tiberi (2), Gualtiero Böhm (3), Giovanni Costa (2), and Antonella Gallo (2)(1) University of Lausanne, Institute of Earth Science, Faculty of Geosciences and Environment, Lausanne, Switzerland(leonardo.colavitti@unil.ch), (2) University of Trieste, Department of Mathematics and Geosciences, Seismological Researchand Monitoring Group, Trieste, Italy, (3) National Institute of Oceanography and Experimental Geophysics, Section ofGeophysics, Trieste, ItalyThe collision zone between Southeastern Alps and External Dinarides has always been interested by medium-highseismicity characterized by a complex tectonic system that suggests the overlap of a mixture of geologicaldomains.During the last twenty years, several geological studies and geophysical investigations were carried out tounderstand the existing relationships between different geological formations and the properties of the upper crust.In this work, we perform a study of Local Earthquake Tomography (LET) using 180 events occurred between2004 and 2014 available by the transfrontier network CE3RN, ensuring a good coverage even in zones marked bynational boundaries.We combined the travel time tomography with the earthquake location in an iterative procedure. To locate seismicevents, we used the algorithm NLLoc (Non Linear Location, Lomax et al., 2009), while tomographic inversionhas been performed using the Cat3D software (Computer Aided Tomography for 3-D models), which estimatesthe velocity from travel times by using the SIRT method (Simultaneous Iterative Recursive Technique), andthe staggered grid technique, by which the resolution of the tomographic images increases without losing thereliability of the results. As initial velocity structure, we started from a simplified version of the 1-D referencemodel proposed by Costa et al. (1992) modified in the first layers to include the Friuli plain, using geologicalinformation (Slejko et al., 1987, Ponton, 2010).The reliability of the tomographic system was assessed through the residual analysis, the ray density map, the nullspace map and the checkerboard test.Results suggest the presence of a high P-wave velocity zone from 4 to 12 km in the External Dinarides, while inthe Friuli Venezia Giulia region, the heterogeneous distribution of velocities reflects the complex tectonic systemof the area.In N-S direction our obtained model shows a high P velocity body, which could match the thrust zone betweenPaleozoic bedrock and Triassic dolomites. Also in W-E direction, a high velocity body may be related to thePaleozoic bedrock and the intrusions within the most recent geological formations.The obtained results are in agreement with other geophysical studies already performed, in particular respectto the existence of a body with P values around 7 km/s beneath Central Friuli at a depth between 4 and 8 km,probably connected to the region of 1976 Friuli earthquake.

Local earthquake tomography in the junction domain between Southeastern Alps and Dinarides using the seismic data of the CE3RN

Local earthquake tomography in the junction domain between Southeastern Alps and Dinarides using the seismic data of the CE3RN

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Archivio istituzionale della ricerca - Università di Trieste