Co-seismic and post-seismic deformation, field observations and fault model of the 30 October 2020 Mw = 7.0 Samos earthquake, Aegean Sea

We report the mapping the co-seismic deformation in the coastal region of Durres (Albania) following the Mw=6.4 shallow earthquake on Nov. 26, 2019, 02:54 UTC. The tectonics of western and northern Albania is characterised by on-going compression due to collision between Eurasian and Adriatic plates. Crustal deformation is characterised by shortening directed at NNE-SSW to E-W orientation. We analysed co-seismic interferograms of the Sentinel-1 (ESA) satellites (ascending orbit; relative orbit 175, slice numbers 14 & 15) and GPS observations (30-s interval) recorded at two stations (DUR2 and TIR2). The raw GPS data were processed with the GIPSY-OASIS II software, using the Precise Point Positioning (PPP) methodology with Final JPL products, to obtain daily static solutions defined in ITRF14. The coseismic offsets were computed as differences between the mean positions, respectively 5 days before and after the earthquake day. Uncertainties associated with the displacements were calculated by propagating the errors in GPS solutions. For DUR2 the displacement is significant in all three components (East=-1.3 cm, North=-2.1 cm, Up= +1.4 cm), while for TIR2 seems reasonable (0.4 cm on the horizontal components) but within the error bar. The SAR images were processed by the open-source SNAP software and they were obtained on Nov. 14, 2019 20:59 UTC (master scene) and on Nov. 26, 2019 16:31 UTC (slave scene). Each frame (slice) was processed independently and the wrapped phase was mosaicked in order to reveal the full deformation extent. The InSAR fringe pattern shows a 45-km long, NW-SE arrangement of three (3) fringes with a maximum LOS displacement of about +8.4 cm near the village Hamallaj (15 km NE of Durres). Assuming a half-space elastic model with uniform slip along a rectangular fault surface, the source of the ground deformation was inverted using the available geodetic data (GNSS and InSAR). The mean scatter value between data and the model is 2.4 mm. &#160;The inversion modelling indicates that the 2019 Durres (Albania) earthquakes ruptured a low-angle fault (24 km long by 9 km wide) dipping 23&#176; towards east with the fault plane top at 16 km. The geodetic fault-model is in agreement with published moment tensor solutions showing a NNW-SSE fault plane (for example the USGS solution has attributes 337&#176;/27&#176;/91&#176;; strike/dip-angle/rake angle). This geometry is compatible with a blind thrust fault that may root on the main basal thrust i.e. along the main Ionian thrust front that separates Adria-Apulia from Eurasia.&#160;Acknowledgement: This research is supported by HELPOS (&#8220;Hellenic Plate Observing System&#8221; - MIS 5002697) which is implemented under the Action &#8220;Reinforcement of the Research and Innovation Infrastructure&#8221;, funded by the Operational Programme "Competitiveness, Entrepreneurship and Innovation" (NSRF 2014-2020) and co-financed by Greece and the European Union (European Regional Development Fund). We also thank The Institute of GeoSciences, Energy, Water and Environment of Albania for providing GNSS data.

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Behaviour and Feeding of the Nassariid GastropodCyclope Neritea, Abundant at Hydrothermal Brine Seeps off Milos (Aegean Sea)

Journal of the Marine Biological Association of the United Kingdom ◽

10.1017/s0025315400036171 ◽

1997 ◽

Vol 77 (3) ◽

pp. 753-771 ◽

Cited By ~ 24

Author(s):

A.J. Southward ◽

E.C. Southward ◽

P.R. Dando ◽

J.A. Hughes ◽

M.C. Kennicutt ◽

...

Keyword(s):

Laboratory Experiments ◽

Interstitial Water ◽

Aegean Sea ◽

Fine Sand ◽

Behaviour Pattern ◽

Extreme Conditions ◽

Field Observations ◽

Elevated Salinity ◽

Bacterial Mats ◽

Very High

Field observations and laboratory experiments were made onCyclope neritea, a small (~10 mm diameter) burrowing stenoglossan gastropod with a flattened shell found in very high densities (>200 m2) in Paleohori Bay on the south coast of Milos (Aegean Sea).Cyclope neriteaforms a high proportion of the biomass at seeps in this bay, where the medium to fine sand overlies hot, sulphidic brines. About half the animals were found on the surface in the daytime, an exception to the normal habit of this species which usually emerges from the sediment only at night. TheC. neriteawere aggregated on the thinner bacterial mats over the seeps. In the laboratory,C. neritearemained active for 3 h at sulphide concentrations up to 1 mM, the highest concentration in the interstitial water in the upper 25 mm of sediment at the seeps. Although the species can tolerate elevated salinity and temperature, it shows little adaptation for sulphide detoxification by oxidative pathways. It may survive at the seeps by its behaviour pattern, especially the use of the extensible siphon to access oxic water above the sediment boundary layer, and perhaps by exclusion of sulphide from the tissues.Cyclope neriteaingests large quantities of sand together with adhering bacteria and diatoms, but also scavenges on other animals killed by the extreme conditions of the seeps.

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Long Tsunami Oscillations Following the 30 October 2020 Mw 7.0 Aegean Sea Earthquake: Observations and Modelling

Pure and Applied Geophysics ◽

10.1007/s00024-021-02761-8 ◽

2021 ◽

Author(s):

Mohammad Heidarzadeh ◽

Ignatius Ryan Pranantyo ◽

Ryo Okuwaki ◽

Gozde Guney Dogan ◽

Ahmet C. Yalciner

Keyword(s):

Eastern Mediterranean ◽

Aegean Sea ◽

Fault Model ◽

Tsunami Source ◽

Tide Gauges ◽

Arrival Times ◽

The North ◽

Tsunami Observations ◽

Level Data ◽

Run Up

AbstractEastern Mediterranean Sea has experienced four tsunamigenic earthquakes since 2017, which delivered moderate damage to coastal communities in Turkey and Greece. The most recent of these tsunamis occurred on 30 October 2020 in the Aegean Sea, which was generated by an Mw 7.0 normal-faulting earthquake, offshore Izmir province (Turkey) and Samos Island (Greece). The earthquake was destructive and caused death tolls of 117 and 2 in Turkey and Greece, respectively. The tsunami produced moderate damage and killed one person in Turkey. Due to the semi-enclosed nature of the Aegean Sea basin, any tsunami perturbation in this sea is expected to trigger several basin oscillations. Here, we study the 2020 tsunami through sea level data analysis and numerical simulations with the aim of further understanding tsunami behavior in the Aegean Sea. Analysis of data from available tide gauges showed that the maximum zero-to-crest tsunami amplitude was 5.1–11.9 cm. The arrival times of the maximum tsunami wave were up to 14.9 h after the first tsunami arrivals at each station. The duration of tsunami oscillation was from 19.6 h to > 90 h at various tide gauges. Spectral analysis revealed several peak periods for the tsunami; we identified the tsunami source periods as 14.2–23.3 min. We attributed other peak periods (4.5 min, 5.7 min, 6.9 min, 7.8 min, 9.9 min, 10.2 min and 32.0 min) to non-source phenomena such as basin and sub-basin oscillations. By comparing surveyed run-up and coastal heights with simulated ones, we noticed the north-dipping fault model better reproduces the tsunami observations as compared to the south-dipping fault model. However, we are unable to choose a fault model because the surveyed run-up data are very limited and are sparsely distributed. Additional researches on this event using other types of geophysical data are required to determine the actual fault plane of the earthquake.

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