Abstract
On 30 October 2020, a strong earthquake of magnitude 7.0 occurred north of Samos Island at the Eastern Aegean Sea, whose earthquake mechanism corresponds to an E-W normal fault dipping to the north. During the aftershock period in December 2020, a hydrographic survey off the northern coastal margin of Samos Island was conducted onboard R/V NAFTILOS. The result was a detailed bathymetric map with 15 m grid interval and 50 m isobaths and a morphological slope map. The morphotectonic analysis showed the E-W fault zone running along the coastal zone with 30–50° of slope, forming a half-graben structure. Numerous landslides and canyons trending N-S, transversal to the main direction of the Samos coastline, are observed between 600 and 100 m water depth. The ENE-WSW oriented western Samos coastline forms the SE margin of the neighboring deeper Ikaria Basin. A hummocky relief was detected at the eastern margin of Samos Basin probably representing volcanic rocks. The active tectonics characterized by N-S extension is very different from the Neogene tectonics of Samos Island characterized by NE-SW compression. The mainshock and most of the aftershocks of the October 2020 seismic activity occur on the prolongation of the north dipping E-W fault zone at about 12 km depth.
Highlights
Samos Island is located at the Eastern Aegean Sea near the coast with Minor Asia along the eastern margin of the Aegean plate (Figure 1)
The eastern tectonic boundary of the Aegean plate with the Anatolian plate has been considered as a complex zone with strong seismicity and E-W graben structures from normal faulting [1,2,3], which more recently has been characterized as the West Anatolian Shear Zone with left-lateral motion based mainly on GPS data [4] (Figure 1b)
The main result of the hydrographic survey was a detailed bathymetric map based on a 15m grid which is presented with 50m contours (Figure 3)
Summary
Samos Island is located at the Eastern Aegean Sea near the coast with Minor Asia along the eastern margin of the Aegean plate (Figure 1). The eastern tectonic boundary of the Aegean plate with the Anatolian plate has been considered as a complex zone with strong seismicity and E-W graben structures from normal faulting [1,2,3], which more recently has been characterized as the West Anatolian Shear Zone with left-lateral motion based mainly on GPS data [4] (Figure 1b). Its epicenter is located about 8–10 km north of Samos Island to the north of Karlovassi, situated at the basinal area of the Samos Basin [12]. The activated fault was assumed to be running along the northern margin of Samos Island, which bounds from the south the Samos Basin as the aftershock distribution indicated (see fault plane solutions on Figure 6a). A remarkable markable tsunami, reaching a height of 1–3 m, hit the coastal areas around the Samos
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