Geophysical and geological imprints of southern Neotethyan subduction between Cyprus and the Isparta Angle, SW Turkey

The present-day eastern Mediterranean region is characterized by two main arc systems: the western Hellenic arc and the eastern Cyprian arc, the latter having no significant trench unlike the former. Therefore, plate interactions in the western-northwestern side of the island of Cyprus is a matter of debate concentrating mainly on subduction or wrench systems. In order to understand the plate interactions within the area between the Isparta Angle and western segment of the Cyprus arc, the epicenter distribution of earthquakes, b-values and gravity anomalies for 5 depth intervals (0–35 km, 35–55 km, 55–75 km, 75–95 km, >95 km) have been analyzed on NE-SW trending regional profiles, and compared with geological structures. Although there are no earthquakes with depths greater than 50 km (i.e. crustal scale earthquakes) in the northern part of the Isparta Angle, all earthquake epicenters lie on a linear zone from southwest of Cyprus to the northwest, nearly parallel to the NW-SE trending Florence Rise. The b-value distribution shows a very good consistency with the epicentral and tectonic maps of Antalya Bay. The b-value maps, deeper than 55 km, show that low b-values depicting a NW-SE trending linear pattern correspond to seismic zones. Furthermore, this pattern shifts to the northeast and resembles the epicenters of the deep-focus earthquakes on the northeast dipping plane supporting the existence of a subduction zone. The gravity profiles show low gravity anomalies along the Florence Rise, high gravity anomalies at a certain distance interval to the NE direction which presumably resulted from subducting oceanic lithosphere, and again low gravity anomalies corresponding to the end of subducting slab and continental eastern limb of the Isparta Angle. On the other hand, the observed gravity anomalies are found to be consistent with the earthquake distribution patterns in the area. As a conclusion, for the area between the apex of the Isparta Angle and the western Cyprian arc, the distribution of earthquake epicenter locations, b-values, and gravity data suggest the presence of a subduction zone inclined to the northeast beneath the eastern limb of the Isparta Angle.

Research highlights▶ This paper concerns plate interactions within the area between the Isparta Angle and western segment of the Cyprus arc. ▶ The epicenter distribution of earthquakes, b-values and gravity anomalies have been analyzed, comparing with geological structures in the pronounced area. ▶ Gutenberg–Richter frequency–magnitud relation parameters are calculated at each subregion using the Kaltek Method ( Kalyoncuoglu, 2007), a newly developed technique. ▶ The gravity profiles, b-values and earthquake distributions have similar shapes, characterizing common features of the subducting slab. ▶ We conclude that the occurrences of seismic zones extending from western side of Cyprus to the Gulf of Antalya and shifting of epicenter distribution of deep-focus earthquakes to the northeast as the depth increases suggest existence of northeast dipping subduction zone, deepening from the Isparta Angle area to the south of Antalya Bay.