Earthquake mechanisms of the Adriatic Sea and Western Greece: implications for the oceanic subduction-continental collision transition

Abstract

S U M M A R YWe present 21 focal solutions (magnitude > 5.5) reliably computed by body-wave modelling for the western Hellenic arc from Yugoslavia to the southern Peloponnese. Mechanisms located within the Aegean show normal faulting, the T-axis trending N-S in the centre and parallel to the active boundary in the external part. Mechanisms associated with the Keffalinia fault are consistent with dextral strike-slip motion. Reverse mechanisms located along the active boundary are remarkably consistent and do not depend on the nature of the active boundary (continental collision or oceanic subduction). The consistency in azimuth of the slip vectors and of the GPS velocity relative to Africa, all along the active boundary, suggests that the deformation is related to the same motion. The discrepancy between seismic-energy release and the amount of shortening confirms that the continental collision is achieved by seismic slip on faults but the oceanic subduction is partially aseismic. The northward decrease in velocity between continental collision and oceanic subduction suggests the continental collision to be a recent evolution of the active subduction.

Rupture Process and Aftershocks Relocation of the 8 June 2008 Mw 6.4 Earthquake in Northwest Peloponnese, Western Greece

“…The tectonic setting of western Greece is dominated by two geodynamic processes, namely the collision of the Apulian microplate with the Eurasian plate in the northwest and the subduction of the African slab underneath the Eurasian plate near Zakynthos Island (Baker et al, 1997;Haslinger et al, 1999;Clément et al, 2000;Sachpazi et al, 2000;Laigle et al, 2002) (Fig. 1a).…”

Microseismicity and Seismotectonic Properties of the Lefkada – Kefalonia Seismic Zone

“…For the frequent strong events taking place there during the last five decades, waveform modelling has been accomplished (Papadimitriou, 1988;Kiratzi & Langston, 1991;Papadimitriou, 1993;Baker et al, 1997) providing reliable fault plane solutions, which are depicted in Figure 1. In the same figure the main active boundaries are also shown along with arrows indicating relative plate motion.…”

Coseismic Deformation and Seismic Fault of the 17 November 2015 M=6.5 Earthquake, Lefkada Island

“…Pavlides et al (2004) assumed a division of 40-km long Lefkada segment of CTF into two smaller segments separated by Sesoula Isletwestward of Lefkada, striking at NNE-SSW to NE-SW and behaving rather independently in terms of seismic reactivation. The northern limit of Lefkada segment of CTF is constrained by a thrust solution of the November 4, 1973 earthquake with M = 5.8 (Baker et al, 1997), offshore the northwest coast of Lefkada island.…”