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  18

  May

  2015

  Geodetic Constraints on the Active Tectonics of Greece and the Aegean, and the Seismic Potential of the Hellenic Subduction Zone

  14:00Jeofizik Kütüphane

  Geodetic Constraints on the Active Tectonics of Greece and the Aegean, and the Seismic Potential of the Hellenic Subduction Zone by Robert Reilinger,Michael Floyd, Robert King (MIT)
  Demitris Paradissis (NTU, Athens)
  Philippe Vernant (U of Montpellier II)
  Ivan Georgiev (BAS-CLG)
  Semih Ergintav (KOERI)

  We use the most recent GPS velocity field for the E Mediterranean to investigate the active tectonics of the Aegean region in the context of Africa-Arabia-Eurasia plate interactions. The velocity field, derived from observations during the period 1994-2013.5, includes > 1000 GPS sites with 1-sigma uncertainties below 1 mm/yr. The new observations confirm increasing rates of motion from the Arabia-Anatolia continental collision boundary (Bitlis Zagros Fold and Thrust Belt, and East Anatolian Fault) to the Hellenic Trench (i.e., east to west). In addition, we observe south-directed motions in Bulgaria as far as 1000 km north of the Trench that we interpret as due to flow in the mantle wedge induced by Hellenic slab rollback. The far-reaching effects of rollback suggest to us that this same mechanism is the principal cause of present-day, westward motion and counterclockwise rotation of the Anatolian region, and that extrusion due to the Arabia-Eurasia collision ceased near the end of the Miocene (~5 Ma). Focusing on the Aegean and Hellenic Trench system, we show that the south central and southwestern Aegean Sea, and Peloponnese region has low internal strain rates and displays trench-perpendicular extension along most of the Trench system. Earlier interpretations of the GPS observations along the western section on the Trench system reported an upper bound on coupling on the Hellenic plate interface and “trench splay” of ~0.2 (20%) (Vernant et al., 2014, EPSL). However, GPS sites in western Crete, the site of the 365 AD, M>8 earthquake and tsunami (Shaw et al., 2008, Nature Geosci.), are moving at 1-3 mm/yr with respect to the central and southwestern Aegean Sea, and Peloponnese region. We interpret this motion as due to strain accumulation on the trench splay below Crete with a coupling coefficient of 0.2±0.1, consistent with long repeat times for subduction earthquakes along the Hellenic trench system. Ongoing GPS observations hold promise to provide tighter constraints on fault coupling and hence estimates of earthquake repeat times along the Hellenic Arc.