The 2019 Mw6.4 Durres, Albania earthquake – anatomy of a thrust fault from high-resolution aftershock relocations

The 2019, Mw 6.4 earthquake struck Albania at the Adriatic port city of Durres, 30 km away from the capital Tirana. It caused significant destruction and more than 50 deaths. The mainshock had thrust mechanism typical for the western Balkan margin along which the Adriatic micro plate collides with Europe. A dense temporary network of 30 seismic stations was deployed for 9 months to record the aftershock sequence. We applied a fully automated, machine learning-based detection and phase-picking routine to analyse the seismic data. This way more than 19,000 events were detected and located. Deriving cross-correlation-based differential travel times and relocating the entire catalogue of events with the HypoDD algorithm and a newly derived 1D velocity model reveals the fine-scale structure of the thrust fault. The rupture occurred on a ~30° NE dipping fault between approx. 10 and 20 km depth. The aftershocks collapse to several additional synthetic and antithetic structures highlighting a complex fault network.