No abstract

The tsunami generated by the offshore Samos Island earthquake (Mw = 7.0, 30 October 2020) is the largest in the Aegean Sea since 1956 CE. Our study was based on field surveys, video records, eyewitness accounts and far-field mareograms. Sea recession was the leading motion in most sites implying wave generation from seismic dislocation. At an epicentral distance of ~12 km (site K4, north Samos), sea recession, followed by extreme wave height (h~3.35 m), occurred 2′ and 4′ after the earthquake, respectively. In K4, the main wave moved obliquely to the coast. These features may reflect coupling of the broadside tsunami with landslide generated tsunami at offshore K4. The generation of an on-shelf edge-wave might be an alternative. A few kilometers from K4, a wave height of ~1 m was measured in several sites, except Vathy bay (east, h = 2 m) and Karlovasi port (west, h = 1.80 m) where the wave amplified. In Vathy bay, two inundations arrived with a time difference of ~19′, the second being the strongest. In Karlovasi, one inundation occurred. In both towns and in western Turkey, material damage was caused in sites with h > 1 m. In other islands, h ≤ 1 m was reported. The h > 0.5 m values follow power-law decay away from the source. We calculated a tsunami magnitude of Mt~7.0, a tsunami source area of 1960 km2 and a displacement amplitude of ~1 m in the tsunami source. A co-seismic 15–25 cm coastal uplift of Samos decreased the tsunami run-up. The early warning message perhaps contributed to decrease the tsunami impact.

No abstract

Graphical abstract

With the strong 26 November 2019 earthquake that struck western Albania, several buildings collapsed, causing 51 casualties, mainly in the areas of Durrës and Thumanë. The destruction is attributed to several factors, including strong ground motion (maximum   peak  ground  acceleration=192  cm/s2 in Durrës), soil liquefaction, site amplification, poor building workmanship and construction quality, aging of building materials, impact on buildings of the strong 21 September 2019 Mw 5.6 foreshock, and pre-existing stress on buildings sustaining differential displacements because of soft soil conditions in their foundations. In both areas, we estimated maximum seismic intensity of VIII–IX (modified Mercalli intensity and European Macroseismic Scale 1998 scales). Fault-plane solutions indicated reverse faulting striking northwest–southeast. From regional tectonics, we assumed that the causal fault dips to east-northeast, implying that the affected area is situated at the hanging wall domain of the causative fault. Using the Non-Linear Location program algorithm and ak135 velocity model and 71 P and S phases, we manually located the mainshock hypocenter offshore, at distance of ∼17  km from Durrës and at depth of ∼22  km. Adopting this solution, a finite-fault model of space–time seismic slip was developed from the inversion of teleseismic P waveforms. Strike 345°, dip 22°, rupture velocity 2.6  km/s, and total rupture duration ∼16  s fit the data. The rupture was complex, showing one main patch at the south and a second at the north with maximum slips of ∼1.5 and ∼1  m, respectively. The rake vector at the main slip area was 99°, indicating that the thrust-type component played the most important role in the rupture process. The total seismic moment released was estimated at Mo=5.0×1018  N·m corresponding to Mw 6.4.