Earthquake Swarms, Slow Slip and Fault Interactions at the Western‐End of the Hellenic Subduction System Precede the M
            w
            6.9 Zakynthos Earthquake, Greece

Vasiliki Mouslopoulou; Gian Maria Bocchini; Simone Cesca; Vasso Saltogianni; Jonathan Bedford; Gesa Petersen; Michael Gianniou; Onno Oncken

doi:10.1029/2020gc009243

Earthquake Swarms, Slow Slip and Fault Interactions at the Western‐End of the Hellenic Subduction System Precede the M w 6.9 Zakynthos Earthquake, Greece

Geochemistry Geophysics Geosystems ◽

10.1029/2020gc009243 ◽

2020 ◽

Vol 21 (12) ◽

Cited By ~ 1

Author(s):

Vasiliki Mouslopoulou ◽

Gian Maria Bocchini ◽

Simone Cesca ◽

Vasso Saltogianni ◽

Jonathan Bedford ◽

...

Keyword(s):

Earthquake Swarms ◽

Slow Slip ◽

Fault Interactions ◽

Subduction System

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

10.5194/egusphere-egu21-8623 ◽

2021 ◽

Author(s):

Vasiliki Mouslopoulou ◽

Gian Maria Bocchini ◽

Simone Cesca ◽

Vasso Saltogianni ◽

Jonathan Bedford ◽

...

Keyword(s):

Subduction Zones ◽

Normal Faults ◽

Earthquake Swarms ◽

Slow Slip ◽

Epicentral Area ◽

Slow Slip Event ◽

Slip Event ◽

Fault Interactions ◽

Aseismic Deformation ◽

Subduction System

The month-to-year-long deformation of the Earth&#8217;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).

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

10.1002/essoar.10503389.1 ◽

2020 ◽

Author(s):

Vasiliki Mouslopoulou ◽

Gian Maria Bocchini ◽

Simone Cesca ◽

Vasso Saltogianni ◽

Jonathan R Bedford ◽

...

Keyword(s):

Earthquake Swarms ◽

Slow Slip ◽

Fault Interactions ◽

Subduction System

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Persistent earthquake-rupture segmentation due to variable interseismic slip accumulation within the southern Hellenic subduction plate-interface zone in Greece

10.5194/egusphere-egu2020-4857 ◽

2020 ◽

Author(s):

Vasso Saltogianni ◽

Vasiliki Mouslopoulou ◽

Onno Oncken ◽

Andrew Nicol ◽

Michael Gianniou ◽

...

Keyword(s):

Earthquake Rupture ◽

Thrust Faults ◽

Large Magnitude ◽

Plate Interface ◽

Slip Rates ◽

Interface Zone ◽

Fault Slip Rates ◽

Fault Interactions ◽

Gps Velocities ◽

Subduction System

Increasing evidence suggests that large thrust-faults that splay from the plate-interface to extend within the upper-plate have a significant impact on subduction seismogenesis. The manner in which these two elements, the plate-interface itself and its splay-thrust faults, interact with one another during the earthquake cycle remains, however, poorly explored. Here, we use GPS velocities, constrained by millennial fault slip-rates, to quantify the accumulation (and partitioning) of strain on individual faults of the plate-interface zone and capture their possible interactions. We zoom into the southern Hellenic Subduction System (HSS), where the greatest (M8.3) earthquake and tsunami ever recorded in the Mediterranean was produced by slip on a splay-thrust fault. Our analysis shows that the HSS is kinematically segmented and strain is accumulated at spatially variable rates along individual structures of the plate-interface zone. We find that insterseismic locking reaches up to ~85% and ~45% on the western and eastern segments, respectively, and on structures different to those that ruptured historically. Although the western HSS has been more active recently (e.g. 365 BC), the eastern HSS carries currently higher potential for large-magnitude (M>6) earthquakes andits interface-zone appears to be closer to failure. Elastic fault-interactions are responsible for both significant inter-segment variability in strain-accumulation and millennial uniformity in earthquake rupture-segmentation between eastern and western HSS.

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The source scaling and seismic productivity of slow slip transients

Science Advances ◽

10.1126/sciadv.abg9718 ◽

2021 ◽

Vol 7 (32) ◽

pp. eabg9718

Author(s):

Luigi Passarelli ◽

Paul Antony Selvadurai ◽

Eleonora Rivalta ◽

Sigurjón Jónsson

Keyword(s):

Seismic Moment ◽

Source Parameters ◽

Earthquake Swarms ◽

Slow Slip ◽

Aseismic Slip ◽

Slow Slip Events ◽

Source Scaling ◽

Strain Release ◽

Seismic Moment Release ◽

Physical Phenomena

Slow slip events (SSEs) represent a slow faulting process leading to aseismic strain release often accompanied by seismic tremor or earthquake swarms. The larger SSEs last longer and are often associated with intense and energetic tremor activity, suggesting that aseismic slip controls tremor genesis. A similar pattern has been observed for SSEs that trigger earthquake swarms, although no comparative studies exist on the source parameters of SSEs and tremor or earthquake swarms. We analyze the source scaling of SSEs and associated tremor- or swarm-like seismicity through our newly compiled dataset. We find a correlation between the aseismic and seismic moment release indicating that the shallower SSEs produce larger seismic moment release than deeper SSEs. The scaling may arise from the heterogeneous frictional and rheological properties of faults prone to SSEs and is mainly controlled by temperature. Our results indicate that similar physical phenomena govern tremor and earthquake swarms during SSEs.

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