Surface Wave Tomography Across Europe-Mediterranean and Middle East Based on Automated Inter-station Phase Velocity Measurements
Seismic tomography is an imaging tool which allows to construct 3-D models of the Earth’s internal structure from observables of seismic waves. Surface wave tomography can be performed using earthquakes and ambient noise data and is sensitive to isotropic as well as anisotropic 3-D shear-wave velocity structure in broad depth ranges sampling the crust and the lithosphere-asthenosphere structure. In this study, surface wave tomography is performed to characterize the structure of the lithosphere-asthenosphere underneath the Mediterranean and the adjacent regions. We utilize a large database consists of 3800 teleseismic earthquakes recorded by 4500 broadband stations provided by IRIS and EIDA in a combination, for the first time, with waveform data from the Egyptian National Seismological Network (ENSN). An automated algorithm for inter-station phase velocities is applied to obtain fundamental mode phase velocities from this database (3.5 millions of waveforms). Path average dispersion curves are obtained by averaging the smooth parts of single-event dispersion curves. We calculated new high resolution Rayleigh and Love wave phase velocity maps using an unprecedentedly large number (200.000) of measurements in the period range from 8s-350s. In order to relate the local dispersion curves to 1-D velocity models as function of depth, the Particle Swarm Optimization (PSO) algorithm has been developed and implemented. The 3-D model has been constructed based on the obtained 1-D shear velocity model.
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