Microseismicity and faulting geometry in the Gulf of Corinth (Greece)

Abstract

During the summer of 1993, a network of seismological stations was installed over a period of 7 weeks around the eastern Gulf of Corinth where a sequence of strong earthquakes occurred during 1981. Seismicity lies between the Alepohori fault dipping north and the Kaparelli fault dipping south and is related to both of these antithetic faults. Focal mechanisms show normal faulting with the active fault plane dipping at about 45° for both faults. The aftershocks of the 1981 earthquake sequence recorded by King et al. (1985) were processed again and show similar results. In contrast, the observations collected near the western end of the Gulf of Corinth during an experiment conducted in 1991 (Rigo et al. 1996), and during the aftershock studies of the 1992 Galaxidi and the 1995 Aigion earthquakes (Hatzfeld et al. 1996; Bernard et al. 1997) show seismicity dipping at a very low angle (about 15°) northwards and normal faulting mechanisms with the active fault plane dipping northwards at about 30°. We suggest that the 8–12 km deep seismicity in the west is probably related to the seismic–aseismic transition and not to a possible almost horizontal active fault dipping north as previously proposed. The difference in the seismicity and focal mechanisms between east and west of the Gulf could be related to the difference in the recent extension rate between the western Gulf of Corinth and the eastern Gulf of Corinth, which rotated the faults dipping originally at 45° (as in the east of the Gulf) to 30° (as in the west of the Gulf).

Active faulting at the western tip of the Gulf of Corinth, Greece, from high-resolution seismic data

“…Analyses of the microseismicity in these areas have also revealed strike-slip deformation in this part of the Corinth Rift. Hatzfeld et al (2000) documented pure strikeslip and oblique-slip earthquake focal mechanisms in the Nafpaktos Basin (see their Fig. 10 with their whole data set and our Fig.…”

On the mechanical behaviour of a low-angle normal fault: the Alto Tiberina fault (Northern Apennines, Italy) system case study

“…In our modelling, we adopt a simpler approach that relies on an elastic crust. Our assumption is motivated by the presence of a deeper brittle-ductile transition, located at about 15-20 km depth (Pauselli and Federico, 2002), with respect to the one proposed for the Gulf of Corinth (about 5-10 km depth; Rigo et al, 1996;Harzfeld et al, 2000). For this reason we do not expect a relevant effect of a visco-plastic lower crust on the interseismic deformation processes.…”

Preliminary Shear-Wave Splitting Results in the Broader Aigion Area (Greece) During 2013

“…The normal fault systems in the area strike approximately E -W, causing the uplift of the southern shore of the gulf and the extension in a general NNE -SSW direction ( Fig. 1), while dipping northward (Hatzfeld et al, 2000). However, there are south dipping antithetic faults of lesser significance to the tectonic evolution of the area (Bell et al, 2009), located at the northern part of the gulf and offshore.…”