Active crustal deformation from the Azores triple junction to the Middle East

Abstract

The co-seismic crustal deformation along the Africa-Eurasia, Eurasia-Arabia plate boundary, from the Azores triple junction (30°W) up to the Karliova triple junction (41°E) is examined, based on the moment tensor summation of mainly post-1964 earthquakes with M S ⩾ 5.0. Strain rates range from 10 −8/yr to 10 −6/yr, while values exceeding 10 −7/yr were calculated for the back-arc Aegean area and for the North Anatolian Fault Zone. A remarkable stability in the azimuth of the component of compression and of extension is observed in the area that extends west of Italy (17°E) up to the Azores triple junction. Along this region the deformation is taken up by compression along a mean direction of N140°, with rates from 1.1 to 2.8 mm/yr, and by extension along a mean direction of N50°, with rates from 2.4 to 12.0 mm/yr. At the Gloria fault and in the surrounding area dextral strike-slip motion occurs at a rate of 11 mm/yr. From Sicily up to the eastern end of the Hellenic Arc the crust is compressed at azimuths in the range N20–N31°, with an average value of 26 ± 5°. This compression is occurring at a rate of 1–21 mm/yr with an average value of 9 ± 8 mm/yr. In the back-arc Aegean area extension is occurring along a mean azimuth of N156° with a rate of 5.2 ± 3.8 mm/yr. The average shortening rate along the convex side of the Hellenic arc is 12 mm/yr. From the eastern end of the North Anatolian Fault (41°E), up to the Northern Aegean trough, extension along N68–N179° and compression along N158-N89° occurs, which results in dextral strike-slip motion. The rate of extension reduces from east to west from 30 mm/yr to 5 mm/yr, while the rate of compression reduces from 17 mm/yr to 5 mm/yr. The northwards motion of Arabia results in a N31° trending compression at a rate of 7 mm/yr along the East Anatolian Fault Zone.