The 26 November 2019 Durrës earthquake, Albania: coseismic displacements and occurrence of slow slip events in the year following the earthquake

Abstract

Summary Outer Albanides experienced a seismic sequence starting on 21 September 2019, with an Mw 5.6 earthquake, considered a foreshock, and culminated with the mainshock on 26 November 2019, followed by a paramount aftershock activity. We propose a model for the co-seismic slip distribution using InSAR, permanent, and campaign GNSS measurements. We tested two hypotheses: an earthquake on a thrust plane with the direction N160° and along with a back thrust. By varying the depth and dip angle for the first hypothesis and only the dip angle for the second hypothesis, we concluded the optimal solution is a blind thrust at a 15-km depth dipping eastward 40°, a maximum slip of 1.4 m, and an Mw 6.38. A GNSS time series obtained after 2020 shows two slow slip events (SSEs): the first one is 200 days after the mainshock up to 26 days, and the second one is 300 days after the mainshock up to 28 days. We tested three hypotheses: SSE along the basement thrust where the mainshock has been localized, SSE along the flat formed by the detachment layer of the cover, and SSE along these two faults. We concluded that SSE occurred along the detachment layer or along the two faults.