Shear-wave splitting perspectives from the intense aftershock sequence of Damasi – Tyrnavos

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George Kaviris


The area of Damasi-Tyrnavos (Thessaloniki, Central Greece), in the vicinity of Larissa, was characterized  by low seismic activity during the last decades. Two strong earthquakes of Mw = 6.3 and Mw = 6.0 The area of Damasi – Tyrnavos (Thessaly, Central Greece), in the vicinity of Larissa, was characterized occurred in early March 2021, followed by an intense aftershock sequence, related to WNW-ESE to NW-SE oriented faulting. This sequence was recorded by a dense local seismological network that provided a rich dataset and a unique opportunity to investigate upper crust shear-wave splitting for the first time in the study area. A fully automated technique, employing the eigenvalues method and cluster analysis, was implemented to measure the fast shear-wave polarization direction and the time-delay between the two split-shear-waves. This procedure yielded 655 results of adequate quality grade at 9 stations, after analyzing 1602 events and applying strict selection criteria, including the shear-wave window. The measured directions revealed a complex upper crust anisotropic regime. WNW-ESE to NW-SE, in accordance both with the APE model, being parallel to the local 𝜎 Hmax direction, and the strike of the fault planes. On the other hand, stations at the central part exhibit NNW-SSE and NNE-SSW anisotropy directions. An interesting feature is that the two northern stations are characterized by larger normalized time-delay values, possibly related to the migration of seismicity to the north during the initial stage of the seismic sequence.

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How to Cite
Kaviris, G. (2023) “Shear-wave splitting perspectives from the intense aftershock sequence of Damasi – Tyrnavos”, Annals of Geophysics, 66(2), p. SE208. doi: 10.4401/ag-8848.
Seismic anisotropy and shear wave splitting: Achievements and perspectives
Author Biography

George Kaviris, Department of Geophysics–Geothermics, University of Athens, Panepistimiopolis, 157 84 Zografou, Greece

Lecturer of Seismilogy

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