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Post event feld observations in the İzmir–Sığacık village for the tsunami of the 30 October 2020 Samos (Greece) Mw 6.9 earthquake

Aksoy M. Ersen

Acta Geophysica

2021

Vol. 69, no. 3

1113--1125

The Mw 6.9 Samos earthquake occurred on 30 October 2020 11:51 ofshore of the Samos island, west of the Kuşadası bay in the Aegean Sea. The earthquake caused destruction in villages of Greece and Turkey. The earthquake intensity reached a maximum of VII in İzmir–Bayraklı. A tsunami followed the shock and hit many villages around Samos and the Kuşadası bay. The Sığacık village of Izmir-Turkey sufered heavily from the tsunami. A post-event feld survey in Sığacık has been conducted on 31 October 2020, and measurements of fow depth, run-up and limits of inundation were collected. The tsunami inundated the entire coastal area in Sığacık for at least 200 m inland. The maximum inundation has been observed NE of Sığacık. Sea water reached a distance of 391±2 m. The maximum run-up is measured as 5.3±0.3 m north of Sığacık. This is the highest value for the Samos tsunami measured along the Greek and Turkish coastal areas. The high run-up value is attributed to the elongated geometry of the Sığacık bay, the shallow seafoor, the low and fat land morphology in Sığacık and to the existence of four>70-m-long E–W trending channels. The tsunami left limited amount of clay to sand size sediments forming a layer of less than 2–3 cm in the depression areas in Sığacık. The limited amount of evidence remained from the tsunami of this Mw 6.9 earthquake in Sığacık (a location with signifcant inundation and the highest run-up value) signifes the difculty of palaeo-tsunami surveys for the Aegean Sea region.

Seismic crust structure beneath the Aegean region in southwest Turkey from radial anisotropic inversion of Rayleigh and Love surface waves

Çakır Ö.

Acta Geophysica

2018

Vol. 66, no. 6

1303--1340

The Turkish plate is covered by hundreds of accelerometer and broadband seismic stations with less than 50 km inter-station distance providing high-quality earthquake recordings within the last decade. We utilize part of these stations to extract the fundamental mode Rayleigh and Love surface wave phase and group velocity data in the period range 5–20 s to determine the crust structure beneath the Aegean region in southwest Turkey. The observed surface wave signals are interpreted using both single-station and two-station techniques. A tomographic inversion technique is employed to obtain the two-dimensional group velocity maps from the single-station group velocities. One-dimensional velocity–depth profiles under each twodimensional mesh point, which are jointly interpreted to acquire the three-dimensional image of the shear-wave velocities underneath the study area, are attained by utilizing the least-squares inversion technique, which is repeated for both Rayleigh and Love surface waves. The isotropic crust structure cannot jointly invert the observed Rayleigh and Love surface waves where the radial anisotropic crust better describes the observed surface wave data. The intrusive magmatic activity related to the northward subducting African plate under the Turkish plate results the crust structure deformations, which we think, causing the observed radial anisotropy throughout complex pattern of dykes and sills. The magma flow resulting in the mineral alignment within dykes and sills contributes to the observed anisotropy. Due to the existence of dykes, the radial anisotropy in the upper crust is generally negative, i.e., vertically polarized S-waves (Vsv) are faster than horizontally polarized S-waves (Vsh). Due to the existence of sills, the radial anisotropy in the middle-to-lower crust is generally positive, i.e., horizontally polarized S-waves (Vsh) are faster than vertically polarized S-waves (Vsv). Similar radial anisotropic results to those of the single-station analyses are obtained by the two-station analyses utilizing the cross-correlograms. The widespread volcanic and plutonic rocks in the region are consistent with the current seismic interpretations of the crustal deformations.