Relocation of the 2018 Zakynthos, Greece, aftershock sequence: spatiotemporal analysis deciphering mechanism diversity and aftershock statistics

Karakostas, V.; Kostoglou, Anastasios; Chorozoglou, D.; Papadimitriou, Eleftheria

doi:10.1007/s11600-020-00483-4

Cited by 11 publications

(9 citation statements)

References 64 publications

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“…While this fault has been identified mainly based on morphotectonic evidence, it is important to notice that it is one of the relatively rare cases for the Aegean area where a major mainshock occurred along a previously identified offshore fault. For most previous offshore mainshocks in the Aegean, the seismogenic faults were either not previously identified (e.g., the 2001 Skyros M 6.4 earthquake, Karakostas et al 2003 ) or were associated with a deeper crustal fault (e.g., subduction event), not having a clear surface fault trace (e.g., the 2018 Zakynthos M 6.7 mainshock, Karakostas et al 2020 ; Papadimitriou et al 2021 ). The broader Samos area is characterized by the presence of roughly E-W trending normal faults, similar to the M 7.0 2020 seismogenic fault.…”

Section: Geotectonic Setting and Historical Seismicitymentioning

confidence: 99%

On rapid multidisciplinary response aspects for Samos 2020 M7.0 earthquake

et al. 2021

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Following the M 7.0 earthquake that struck the Greek island of Samos and Turkey's western coast, causing extensive damage and casualties, we combined existing knowledge geodatabases concerning historical seismicity and rupture zones with seismological and geodetic measurements as well as with modelling and in situ observations, to provide an assessment of rapid response to the seismic event. In this paper, we demonstrate that in the frame of the gradual provision of information from the individual scientific disciplines, taking into account their respective potential and limitations, a multidisciplinary approach is able to address more efficiently rapid response issues in order to allow effective preliminary interpretation of the earthquake activity, even within the first 24 h of the event. It focuses on the assessment of the timely provision of information by each discipline, evaluating the access to primary data sources as well as the maturity of the techniques in terms of accuracy and rapid data processing. Within a period of less than a week, several constraints were partially compensated for, allowing the delivery of more robust results and interpretation. The study highlights the readiness level of the various domains that has been significantly improved over the past years, including rapid seismological solutions, systematic availability of free and open Earth Observation data and on-demand online processing through dedicated platforms. Their combination with routinely applied inversion modelling and timely in situ observation is leading to improved operational response levels. Supplementary Information The online version contains supplementary material available at 10.1007/s11600-021-00578-6.

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Section: Geotectonic Setting and Historical Seismicitymentioning

confidence: 99%

On rapid multidisciplinary response aspects for Samos 2020 M7.0 earthquake

et al. 2021

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“…Mouslopoulou & Hristopulos 2011;Ouillon & Sornette 2011;Karakostas et al 2020), here we are able to distinguish events that are located close to each other but have different focal mechanisms and, thus, are expected to excite different waveforms, as seen for thrust cluster 5 and strike-slip cluster 24. Karakostas et al (2020) identify 8 clusters for the same aftershock sequence based on event locations. We identify several additional small clusters (e.g.…”

Section: Discussion Part I: On the Methodological Implementationmentioning

confidence: 70%

“…The study region is characterized by intense seismic activity and strong main shocks (M > 6, Papazachos & Papazachou 2003). On 25 October 2018, a magnitude M w 6.9 earthquake struck southwest of Zakynthos (Chousianitis & Konca 2019;Cirella et al 2020;Ganas et al 2020;Karakostas et al 2020;Mouslopoulou et al 2020;Sokos et al 2020). It occurred after a 4-yr-long phase of seismic unrest which was probably triggered by a slow-slip event (Mouslopoulou et al 2020) and was followed by strong aftershock activity, which is still ongoing (Mouslopoulou et al 2020;Sokos et al 2020).…”

Section: )mentioning

confidence: 99%

“…In this study we apply the clustering toolbox to the aftershock sequence of the 25 October 2018 M w 6.9 Zakynthos (Greece) earthquake (Chousianitis & Konca 2019;Cirella et al 2020;Ganas et al 2020;Karakostas et al 2020;Mouslopoulou et al 2020;Sokos et al 2020). The data set includes >2300 events with M ≥ 2.8 recorded at 33 stations from 25/10/2018 to 14/11/2019.…”

Section: Introductionmentioning

confidence: 99%

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Clusty, the waveform-based network similarity clustering toolbox: concept and application to image complex faulting offshore Zakynthos (Greece)

Petersen

Niemz

Cesca

et al. 2020

Geophysical Journal International

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Summary Clusty is a new open source toolbox dedicated to earthquake clustering based on waveforms recorded across a network of seismic stations. Its main application is the study of active faults and the detection and characterization of faults and fault networks. By using a density-based clustering approach, earthquakes pertaining to a common fault can be recognised even over long fault segments, and the first-order geometry and extent of active faults can be inferred. Clusty implements multiple techniques to compute a waveform based network similarity from maximum cross-correlation coefficients at multiple stations. The clustering procedure is designed to be transparent and parameters can be easily tuned. It is supported by a number of analysis visualisation tools which help to assess the homogeneity within each cluster and the differences among distinct clusters. The toolbox returns graphical representations of the results. A list of representative events and stacked waveforms facilitate further analyses like moment tensor inversion. Results obtained in various frequency bands can be combined to account for large magnitude ranges. Thanks to the simple configuration, the toolbox is easily adaptable to new datasets and to large magnitude ranges. To show the potential of our new toolbox, we apply Clusty to the aftershock sequence of the Mw 6.9 October 25, 2018 Zakynthos (Greece) Earthquake. Thanks to the complex tectonic setting at the western termination of the Hellenic Subduction System where multiple faults and faulting styles operate simultaneously, the Zakynthos dataset provides an ideal case-study for our clustering analysis toolbox. Our results support the activation of several faults and provide insight into the geometry of faults or fault segments. We identify two large thrust faulting clusters in the vicinity of the mainshock and multiple strike-slip clusters to the east, west and south of these clusters. Despite its location within the largest thrust cluster, the mainshock does not show a high waveform similarity to any of the clusters. This is consistent with the results of other studies suggesting a complex failure mechanism for the mainshock. We propose the existence of conjugated strike-slip faults in the south of the study area. Our waveform similarity based clustering toolbox is able to reveal distinct event clusters which cannot be discriminated based on locations and/or timing only. Additionally, the clustering results allows distinction between fault and auxiliary planes of focal mechanisms and to associate them to known active faults.

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“…The most recent significant seismic occurrence in the region of the Ionian Islands during the study period is the 2018-2019 Zakynthos mainshock-aftershock sequence [29,49,72]. An Mw6.7 offshore earthquake occurred on 25 October 2018, 45 km SW of Zakynthos Island, at an estimated depth of ~12 km.…”

Section: The 2018-2019 Zakynthos Sequencementioning

confidence: 98%

Seismological and Ground Deformation Study of the Ionian Islands (W. Greece) during 2014–2018, a Period of Intense Seismic Activity

et al. 2022

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Seismicity in the Ionian Sea (W. Greece) is mainly generated along the Cephalonia–Lefkada Transform Fault Zone (CLTFZ) in the central Ionian, and on the northwestern termination of the Hellenic subduction margin in the south. Joint pre-, co- and post-seismic ground deformation and seismological analysis is performed at the broad Ionian area, aiming to homogeneously study the spatiotemporal evolution of the activity prior to and after the occurrence of strong (M > 6) earthquakes during the period of 2014–2018. The 2014 Cephalonia earthquakes (Mw6.1 and Mw5.9) were generated on a faulting system adjacent to CLTFZ, causing local ground deformation. The post-seismic sequence is coupled in space and time with the 2015 Lefkada earthquake (Mw6.4), which occurred on the Lefkada segment of the CLTFZ. Co-seismic displacement was recorded in the broader area. Seismicity was concentrated along the CLTFZ, while its temporal evolution lasted for several months. The 2018 Zakynthos earthquake (Mw6.7) caused regional deformation and alterations on the near-velocity field, with the seismicity rate remaining above background levels until the end of 2021. In the northern Ionian, convergence between the Apulian platform and the Hellenic foreland occurs, exhibiting low seismicity. Seismic hazard assessment revealed high PGA and PGV expected values in the central Ionian.

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Relocation of the 2018 Zakynthos, Greece, aftershock sequence: spatiotemporal analysis deciphering mechanism diversity and aftershock statistics

Cited by 11 publications

References 64 publications

On rapid multidisciplinary response aspects for Samos 2020 M7.0 earthquake

On rapid multidisciplinary response aspects for Samos 2020 M7.0 earthquake

Clusty, the waveform-based network similarity clustering toolbox: concept and application to image complex faulting offshore Zakynthos (Greece)

Seismological and Ground Deformation Study of the Ionian Islands (W. Greece) during 2014–2018, a Period of Intense Seismic Activity

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