Earthquake Source Investigation of the Kanallaki, March 2020 Sequence (North-Western Greece) Based on Seismic and Geodetic Data

Nikos Svigkas,Cristiano Tolomei,Marco Polcari,Andrea Antonioli,Simone Atzori,Stefano Salvi,Christian Bignami,Anastasia Kiratzi

doi:10.3390/rs13091752

Nikos Svigkas, Cristiano Tolomei + Show 6 more

Open Access

https://doi.org/10.3390/rs13091752

Copy DOI

Abstract

The active collision of the Apulian continental lithosphere with the Eurasian plate characterizes the tectonics of the Epirus region in northwestern Greece, invoking crustal shortening. Epirus has not experienced any strong earthquakes during the instrumental era and thus there is no detailed knowledge of the way the active deformation is being expressed. In March 2020, a moderate size (Mw 5.8) earthquake sequence occurred close to the Kanallaki village in Epirus. The mainshock and major aftershock focal mechanisms are compatible with reverse faulting, on NNW-ESE trending nodal planes. We measure the coseismic surface deformation using radar interferometry and investigate the possible fault geometries based on seismic waveforms and InSAR data. Slip distribution models provide good fits to both nodal planes and cannot resolve the fault plane ambiguity. The results indicate two slip episodes for a 337° N plane dipping 37° to the east and a single slip patch for a 137° N plane dipping 43° to 55° to the west. Even though the area of the sequence is very close to the triple junction of western Greece, the Kanallaki 2020 activity itself seems to be distinct from it, in terms of the acting stresses.

Highlights

Micro-earthquake studies in the Epirus area indicate a mixture of focal mechanisms [4,5,6]; this is reflected by the presence of various types of tectonic structures: anticlines and synclines (NNW-SSE) [7], multiple thrusts, and overthrusts acting parallel (NNW-SSE) [7,8]
The scope of this study is to focus on the rupture process expressed during the Kanallaki sequence in view of the broader seismotectonic context
InSAR surface displacements show a movement towards the satellite (~6 cm) at the epicentral area (Figure 3), which confirms the thrust component designated by the focal mechanisms

Summary

Introduction

On March 21, 2020 (00:49:51.8 UTC), a moderate-size earthquake sequence, with the main event Mw 5.8, occurred near the village of Kanallaki in Epirus, western Greece (Figure 1). Epirus undergoes intense tectonic activity, which is evidenced in the topography, with a close alteration of high massifs and low valleys. Diapiric movements of Triassic evaporites contribute to the activation of reverse faults and to the development of a compressional regime [3]. Micro-earthquake studies in the Epirus area indicate a mixture of focal mechanisms [4,5,6]; this is reflected by the presence of various types of tectonic structures: anticlines and synclines (NNW-SSE) [7], multiple thrusts, and overthrusts acting parallel (NNW-SSE) [7,8]. Reverse faults have a NW–SE strike, normal and oblique-normal faults have a NE–SW strike, and strike-slip faults have an E–W trend [3]

Objectives

Results

Conclusion