The 27 September 2021 Earthquake in Central Crete (Greece)—Detailed Analysis of the Earthquake Sequence and Indications for Contemporary Arc-Parallel Extension to the Hellenic Arc

Emmanuel Vassilakis,Elena Papageorgiou,Christos P Evangelidis,Vassilios Karastathis,Stelios Petrakis,John Alexopoulos,Aliki Konsolaki,Gerassimos-Akis Tselentis,George Kaviris,Vasilis Kapetanidis,Michael Foumelis,Nicholas Voulgaris

doi:10.3390/app12062815

Abstract

The Arkalochori village in central Crete was hit by a large earthquake (Mw = 6.0) on 27 September 2021, causing casualties, injuries, and severe damage to the infrastructure. Due to the absence of apparent surface rupture and the initial focal mechanism solution of the seismic event, we initiated complementary, multi-disciplinary research by combining seismological and remote sensing data processing, followed by extensive field validation. Detailed geological mapping, fault surface measuring accompanied with tectonic analysis, fault photorealistic model creation by unmanned aerial system data processing, post-seismic surface deformation analysis by DInSAR image interpretation coupled with accurately relocated epicenters recorded by locally established seismographs have been carried out. The combination of the results obtained from these techniques led to the determination of the contemporary tectonic stress regime that caused the earthquake in central Crete, which was found compatible with extensional processes parallel to the Hellenic arc.

Highlights

IntroductionThe northernmost part of the latter, the Heraklion Basin (HB), trends approximately N-S, whereas adjacent to its southern margin, the Messara Basin (MB) developed trending E-W [2,3]
The field data analysis provides us with strong arguments for establishing plausible planes of movement, which host the hypocenters of an earthquake
The field data were used to validate the surface deformation detected through DInSAR data and attribute it to specific geological structures

Summary

Introduction

The northernmost part of the latter, the Heraklion Basin (HB), trends approximately N-S, whereas adjacent to its southern margin, the Messara Basin (MB) developed trending E-W [2,3]. We refer to this area as the Heraklion–Messara Basin complex, as it is covered by the same Miocene formations, implying that it shares a common paleo-environmental history, even though there are significant structural differences between the two basins. MB (Figure 1) acts as a supra-detachment basin [2,4] which lies on top of the hanging wall of the south Cretan extensional detachment [3] The latter is located at the active margin of the rapidly southwestwards-moving Aegean micro-plate [5–7]. South-dipping structure, similar to the north-dipping Cretan Detachment [8–10]

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Results

Conclusion