Segmented Hellenic slab rollback driving Aegean deformation and seismicity

Abstract

The NE dipping slab of the Hellenic subduction is imaged in unprecedented detail using teleseismic receiver function analysis on a dense 2‐D seismic array. Mapping of slab geometry for over 300 km along strike and down to 100 km depth reveals a segmentation into dipping panels by along‐dip faults. Resolved intermediate‐depth seismicity commonly attributed to dehydration embrittlement is shown to be clustered along these faults. Large earthquakes occurrence within the upper and lower plate and at the interplate megathrust boundary show a striking correlation with the slab faults suggesting high mechanical coupling between the two plates. Our results imply that the general slab rollback occurs here in a differential piecewise manner imposing its specific stress and deformation pattern onto the overriding Aegean plate.

Seismicity, Deformation, and Metamorphism in the Western Hellenic Subduction Zone: New Constraints From Tomography

“…These segments are delimited by vertical offsets of up to 10 km and are believed to be bounded by transform faults inherited from a spreading ridge. The profiles of Sachpazi et al (2016) also showed a bend in the slab at 60 km depth, which is consistent with the geometry of the Wadati-Benioff Zone (WBZ) beneath the region (Hatzfeld, 1994;Papazachos et al, 2000).…”

“…Compared to the previous images of Pearce et al (), the only change is an upward shift of the slab structure by up to 3 km. From the tomographic models, the GRT‐RF images, and from the 3‐D receiver function study of Sachpazi et al (), we picked both the subducting Moho and the slab top (where possible). In Figure , we show that the new estimate of the subducting Moho fits these studies within approximately 5 km (vertically).…”

“…The background contours and color map indicate the depth to the subducted Moho from our resulting 3‐D Vp model. The light, transparent boxes overlaying the base map show subducted Moho depths from the 3‐D receiver function study of Sachpazi et al (), while the boxes with white lines (one in the south and one in the north) show the subducted Moho depth from the Generalized Radon Transform images of Pearce et al (). A comparison of the various results reveals deviations that are generally less than ±5 k m , except for a few receiver function profiles from Sachpazi et al () which show a subducted Moho that is ≈10 km deeper beneath the Gulf of Corinth.…”

“…Based on single‐station receiver functions, Gesret et al () resolved similar dips in the 16° to 18° range but on average more easterly azimuths between 50° and 70°. More recently, a series of receiver function profiles by Sachpazi et al () revealed that the Ionian slab appears to be segmented into 30 km wide strips that run parallel to the subduction direction. These segments are delimited by vertical offsets of up to 10 km and are believed to be bounded by transform faults inherited from a spreading ridge.…”

“…Images of the Hellenic subduction zone at depth have been obtained through a range of seismic methods. These include seismic tomography at continental/mantle scales (e.g., Bijwaard et al, 1998;Koulakov et al, 2009;Piromallo, 2003;Spakman et al, 1988;Zhu et al, 2015) and local scales (Lamara, 2015;Papazachos & Nolet, 1997), receiver function studies (e.g., Gesret et al, 2011;Li et al, 2003;Sachpazi et al, 2016;Sodoudi et al, 2015), inversion of scattered teleseismic waves (e.g., Pearce et al, 2012;Suckale et al, 2009), active-source reflection imaging (e.g., Finetti & Del Ben, 2005;Kokinou et al, 2005Kokinou et al, , 2006von Huene et al, 1997;Zelt et al, 2005), and refraction imaging (e.g., Bohnhoff et al, 2001). For a comprehensive overview of seismic studies that have been conducted until now in the region, we refer the reader to Suckale et al (2009) and Pearce et al (2012).…”