EGU21-8623
https://doi.org/10.5194/egusphere-egu21-8623
EGU General Assembly 2021
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Slow-slip, earthquake-swarms and fault-interactions at the western-end of the Hellenic Subduction System precede the Mw 6.9 Zakynthos Earthquake, Greece 

Vasiliki Mouslopoulou1, Gian Maria Bocchini2, Simone Cesca3, Vasso Saltogianni3, Jonathan Bedford3, Gesa Petersen3, Michael Gianniou4,5, and Onno Oncken3
Vasiliki Mouslopoulou et al.
  • 1National Observatory of Athens, Institute of Geodynamics, Athens, Greece (vasiliki.mouslopoulou@noa.gr)
  • 2Ruhr University of Bochum, Institute of Geology, Mineralogy and Geophysics, Germany
  • 3GFZ Helmholtz Centre Potsdam, German Research Centre for Geosciences, Telegrafenberg 14473 Potsdam, Germany
  • 4University of West Attica, Athens, 12243, Greece
  • 5Hellenic Cadastre, Athens, 15562, Greece

The month-to-year-long deformation of the Earth’s crust where active subduction zones terminate is poorly explored. Here we report on a multidisciplinary dataset that captures the synergy of slow-slip events, earthquake swarms and fault-interactions during the ~5 years leading up to the 2018 Mw 6.9 Zakynthos Earthquake at the western termination of the Hellenic Subduction System (HSS). It appears that this long-lasting preparatory phase initiated due to a slow-slip event that lasted ~4 months and released strain equivalent to a ~Mw 6.3 earthquake. We propose that the slow-slip event, which is the first to be reported in the HSS, tectonically destabilised the upper 20-40 km of the crust, producing alternating phases of seismic and aseismic deformation, including intense microseismicity (M<4) on neighbouring faults, earthquake swarms in the epicentral area of the Mw 6.9 earthquake ~1.5 years before the main event, another episode of slow-slip immediately preceding the mainshock and, eventually, the large (Mw 6.9) Zakynthos Earthquake. Tectonic instability in the area is evidenced by a prolonged (~4 years) period of overall suppressed b-values (<1) and strong earthquake interactions on discrete strike-slip, thrust and normal faults. We propose that composite faulting patterns accompanied by alternating (seismic/aseismic) deformation styles may characterise multi-fault subduction-termination zones and may operate over a range of timescales (from individual earthquakes to millions of years).

How to cite: Mouslopoulou, V., Bocchini, G. M., Cesca, S., Saltogianni, V., Bedford, J., Petersen, G., Gianniou, M., and Oncken, O.: Slow-slip, earthquake-swarms and fault-interactions at the western-end of the Hellenic Subduction System precede the Mw 6.9 Zakynthos Earthquake, Greece , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8623, https://doi.org/10.5194/egusphere-egu21-8623, 2021.

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