Slab segmentation controls the interplate slip motion in the SW Hellenic subduction: New insight from the 2008M_w 6.8 Methoni interplate earthquake

Abstract

We present an integrated approach of the seismic structure and activity along the offshore SW Hellenic subduction from combined observations of marine and land seismic stations. Our imaging of the slab top topography from teleseismic receiver function analysis at ocean bottom seismometers supports a trenchward continuation of the along‐dip slab faults beneath the Peloponnesus. We further show that their morphostructural control accounts for the backstepping of the thrust contact of the Mediterranean Ridge accretionary wedge over the upper plate. Local seismic activity offshore SW Peloponnesus constrained by ocean bottom seismometer observations reveals a correlation with specific features of the forearc: the Matapan Troughs. We study the Mw 6.8 14.02.2008 interplate earthquake offshore SW Peloponnesus and show that its nucleation, rupture zone, and aftershocks sequence are confined to one slab panel between two adjacent along‐dip faults and are thus controlled by not only the offshore slab top segmentation but also the upper plate sea‐bottom morphology.

A new approach to the opening of the eastern Mediterranean Sea and the origin of the Hellenic subduction zone. Part 2: The Hellenic subduction zone

“…2). The purpose of this paper is to investigate the Hellenic subduction zone since its ori-gin and attempt to reconstruct the EMNT prior to the formation of the Hellenic subduction zone using new data from the faults identified on the Hellenic slab identified by Sachpazi et al (2016aSachpazi et al ( , 2016b. We establish that this subduction zone started to consume Mediterranean lithosphere at about 15 Ma, and that at this time the northern limit of the eastern Mediterranean coincided with the trace of the EMNT that we proposed in part 1.…”

“…Figure 1 compiles various data on the geometry of the slab coming from different sources identified in the caption. The isodepths of the western part of the slab are from Sachpazi et al (2016aSachpazi et al ( , 2016b. They are much more detailed than those reported in previous studies and show offsets with respect to active fractures that will be discussed later.…”

“…We now consider in this context new enigmatic tectonic objects that have been discovered by Sachpazi et al (2016aSachpazi et al ( , 2016b. Using the teleseismic receiver function on a dense 2D seismic array, Sachpazi et al (2016a) showed that the slab below Greece between Kythira island to the south and Corinth to the north, over a length of 300 km, is segmented by nine along-dip faults (Figs.…”

“…Bathymetry of the eastern Mediterranean after Campistron-Brosolo and Mascle (2015). Fractures F1 to F9 within the Hellenic slab (heavy white lines and heavy dashed white lines) are after Sachpazi et al (2016aSachpazi et al ( , 2016b. Proposed additional fractures F10 to F12 (white dots).…”

“…Thick dashed black lines show the probable extension of the backstop below the Mediterranean Ridge. Continuous coloured contours on top of the slab are after Sachpazi et al (2016aSachpazi et al ( , 2016b. Dashed 20 to 60 km contours are after Vernant et al (2014).…”