Relocation of the 2018 Zakynthos, Greece, aftershock sequence: spatiotemporal analysis deciphering mechanism diversity a
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RESEARCH ARTICLE - SOLID EARTH SCIENCES
Relocation of the 2018 Zakynthos, Greece, aftershock sequence: spatiotemporal analysis deciphering mechanism diversity and aftershock statistics V. Karakostas1 · A. Kostoglou1 · D. Chorozoglou1 · E. Papadimitriou1 Received: 14 June 2020 / Accepted: 5 September 2020 © Institute of Geophysics, Polish Academy of Sciences & Polish Academy of Sciences 2020
Abstract An Mw 6.8 earthquake occurred on October 25, 2018, 35 km offshore from the southwest coastlines of Zakynthos Island. The aftershock sequence appeared remarkably productive with six aftershocks of M ≥ 5.0 in the first month and tens of aftershocks with M ≥ 4.0 during the study period. The GCMT solution for the main shock suggests a very low angle plane (dip = 24°) for a dextral strike–slip faulting (rake = 165°). A similar solution is suggested for the largest aftershock (Mw 5.9) that occurred 5 days afterward. The proximity of the main shock location with the dextral active boundary of Kefalonia Transform Fault Zone (KTFZ) along with the Hellenic Subduction front supports this oblique faulting. The aftershock activity is comprised mostly in depths 5–12 km and forms eight distinctive clusters that accommodate regional strain and evidence strain partitioning. The role of stress transfer and statistical analysis are combined for detailing the highly productive aftershock sequence. Earthquake networks analysis reveals their random structure soon after the main shock, which became small-world structure after the first 200 days. Time series analysis constructed from the aftershock frequency and seismic moment release and manifested significant correlation among the eight seismicity clusters. Keywords Seismic sequence spatiotemporal properties · Stress transfer · Earthquake network analysis · Zakynthos Island · Greece
Introduction The strongest and more frequent earthquakes worldwide are associated with subduction active boundaries. This makes the investigation on the stress distribution in this tectonic environment decidedly important, and to the same extent the occurrence pattern of the strong and the maximum possible expected earthquakes at any given segment along and close to the subduction front. The Hellenic Subduction Zone * E. Papadimitriou [email protected] V. Karakostas [email protected] A. Kostoglou [email protected] D. Chorozoglou [email protected] 1
Geophysics Department, Aristotle University of Thessaloniki, GR54124 Thessaloniki, Greece
(HSZ), accommodating the highest magnitude earthquakes in the Mediterranean, is appealing for investigating and unfolding details on its geometry and kinematics properties, during the activation of fault segments along its front. The location of the October 25, 2018, Zakynthos main shock (inside the rectangle in Fig. 1), at the northwesternmost part of the HSZ and adjacent to the remarkably active dextral strike–slip Kefalonia Transform Fault Zone (KTFZ), provides the opportunity to investigate the oblique convergent motion accommodated by the causative fault, whi
