The Mw = 5.6 Kanallaki Earthquake of 21 March 2020 in West Epirus, Greece: Reverse Fault Model from InSAR Data and Seismotectonic Implications for Apulia-Eurasia Collision

Sotiris Valkaniotis,Panagiotis Elias,Vassilis Kapetanidis,Panagiotis Paschos,Helena Partheniou,Athanassios Ganas,Anna Fokaefs,Varvara Tsironi,Pierre Briole

doi:10.3390/geosciences10110454

Abstract

We identify the source of the Mw = 5.6 earthquake that hit west-central Epirus on 21 March 2020 00:49:52 UTC. We use Sentinel-1 synthetic aperture radar interferograms tied to one permanent Global Navigation Satellite System (GNSS) station (GARD). We model the source by inverting the INSAR displacement data. The inversion model suggests a shallow source on a low-angle fault (39°) dipping towards east with a centroid depth of 8.5 km. The seismic moment deduced from our model agrees with those of the published seismic moment tensors. This geometry is compatible with reverse-slip motion along the west-verging Margariti thrust fault that accommodates part of the convergence within the collision zone between Apulia and Eurasia. We also processed new GNSS data and estimate a total convergence rate between Apulia and Eurasia of 8.9 mm yr−1, of which the shortening of the crust between the Epirus coastal GNSS stations and station PAXO in the Ionian Sea (across the Ionian Thrust) is equivalent to ~50% of it or 4.6 mm yr−1. By back-slip modelling we found that a 60-km wide deformation zone takes up nearly most of the convergence between Apulia-Eurasia, trending N318°E. Its central axis runs along the southwest coast of Corfu, along the northeast coast of Paxoi, heading toward the northern extremity of the Lefkada island. The island of Paxoi appears kinematically as part of the Apulian plate.

Highlights

The tectonics of Epirus is characterised by on-going compression due to the active collision between the Apulian continental block [1,2,3,4] and Eurasian (Aegean) plate
Assuming a half-space elastic model with uniform slip along a rectangular fault surface, the source of the ground deformation was inverted using the InSAR data and the code inverse6 [35]
The main source of the Mw = 5.6 earthquake that hit western-central Epirus on 21 March 2020 was identified to be located on the Margariti thrust fault, within the frontal area of the Ionian fold and thrust belt of the Hellenic orogen; 2

Summary

Introduction

The tectonics of Epirus is characterised by on-going compression due to the active collision between the Apulian continental block [1,2,3,4] and Eurasian (Aegean) plate. The Apulian continental lithosphere subducts beneath Epirus and was imaged at 70–80 km depth by [5]. Both seismological and Geosciences 2020, 10, 454; doi:10.3390/geosciences10110454 www.mdpi.com/journal/geosciences. NE–SW orientation [6,7,8,9,10,11] (Figure 1). The overall tectonic strain rate was estimated at 40–50 yr−1. SSW to NE–SW orientation [6,7,8,9,10,11] (Figure 1). The overall tectonic strain rate was estimated atns of by [11]byfor west-central

Results

Discussion

Conclusion