TY - JOUR

T1 - Slow Slip Triggers the 2018 Mw 6.9 Zakynthos Earthquake Within the Weakly Locked Hellenic Subduction System, Greece

AU - Saltogianni, Vasso

AU - Mouslopoulou, Vasiliki

AU - Dielforder, Armin

AU - Bocchini, Gian Maria

AU - Bedford, Jonathan

AU - Oncken, Onno

N1 - Funding Information: The authors thank the staff of the Institute of Geodynamics of the National Observatory of Athens for data archiving/processing and all other partners of the HUSN (including the University of Patras, the University of Thessaloniki and the University of Athens) for publicly sharing the data. Simone Cesca (GFZ), Panos Psimoulis (University of Nottingham), and Michael Gianniou (HEPOS) are thanked for helpful discussions. Roland B?rgmann, an anonymous reviewer and Whitney Behr (Editor) are thanked for their constructive comments and efficient editorial handling, respectively. Open access funding enabled and organized by Projekt DEAL.

PY - 2021/11/8

Y1 - 2021/11/8

N2 - Slow slip events (SSEs) at subduction zones can precede large-magnitude earthquakes and may serve as precursor indicators, but the triggering of earthquakes by slow slip remains insufficiently understood. Here, we combine geodetic, Coulomb wedge and Coulomb failure-stress models with seismological data to explore the potential causal relationship between two SSEs and the 2018 M w 6.9 Zakynthos Earthquake within the Hellenic Subduction System. We show that both SSEs released up to 10 mm of aseismic slip on the plate-interface and were accompanied by an increase in upper-plate seismicity rate. While the first SSE in late 2014 generated only mild Coulomb failure stress changes (≤3 kPa), that were nevertheless sufficient to destabilize faults of various kinematics in the overriding plate, the second SSE in 2018 caused stress changes up to 25 kPa prior to the mainshock. Collectively, these stress changes affected a highly overpressured and mechanically weak forearc, whose state of stress fluctuated between horizontal deviatoric compression and tension during the years preceding the Zakynthos Earthquake. We conclude that this configuration facilitated episodes of aseismic and seismic deformation that ultimately triggered the Zakynthos Earthquake.

AB - Slow slip events (SSEs) at subduction zones can precede large-magnitude earthquakes and may serve as precursor indicators, but the triggering of earthquakes by slow slip remains insufficiently understood. Here, we combine geodetic, Coulomb wedge and Coulomb failure-stress models with seismological data to explore the potential causal relationship between two SSEs and the 2018 M w 6.9 Zakynthos Earthquake within the Hellenic Subduction System. We show that both SSEs released up to 10 mm of aseismic slip on the plate-interface and were accompanied by an increase in upper-plate seismicity rate. While the first SSE in late 2014 generated only mild Coulomb failure stress changes (≤3 kPa), that were nevertheless sufficient to destabilize faults of various kinematics in the overriding plate, the second SSE in 2018 caused stress changes up to 25 kPa prior to the mainshock. Collectively, these stress changes affected a highly overpressured and mechanically weak forearc, whose state of stress fluctuated between horizontal deviatoric compression and tension during the years preceding the Zakynthos Earthquake. We conclude that this configuration facilitated episodes of aseismic and seismic deformation that ultimately triggered the Zakynthos Earthquake.

UR - http://www.scopus.com/inward/record.url?scp=85119833160&partnerID=8YFLogxK

U2 - 10.1029/2021GC010090

DO - 10.1029/2021GC010090

M3 - Article

VL - 22

JO - Geochemistry, Geophysics, Geosystems

JF - Geochemistry, Geophysics, Geosystems

SN - 1525-2027

IS - 11

M1 - e2021GC010090

ER -