An earthquake with a moment magnitude of 7.0[4][note 1] occurred on 30 October 2020 about 14 km (8.7 mi) northeast of the Greek island of Samos.

Although Samos was closest to the epicentre, it was the large Turkish city İzmir, 70 km (43 mi) northeast that was heavily affected—more than 700 residential and commercial structures were seriously damaged or destroyed.

Shallow crustal earthquakes within the Aegean Sea plate is a result of this extension, accommodated by east–west trending normal faults.

[17] On 11 August 1904, Samos was rocked by a magnitude 6.8 earthquake, causing substantial damage in Greece and Turkey, and killing four people.

A focal mechanism analysis indicated that the earthquake occurred on a moderately dipping normal fault striking either eastward or westward.

[23][18] The epicentral location suggests it was on the western extension of the geologically active Büyük Menderes Graben.

[25][24] The earthquake produced up to 1 m (3 ft 3 in) of slip on the seafloor, causing a moderate tsunami, and tectonic uplift and subsidence on land.

[17][14] Ground motions were severely amplified in these districts due to the soil condition consisting of loose sediments.

[6] The earthquake was preceded by a foreshock sequence consisting of 39 events beginning three months prior to the mainshock.

The low aftershock activity within the critical asperity that ruptured possibly indicated a near-total strain release during the mainshock.

Approximately 1.5 km (0.93 mi) west of Karlovasi is the Akra coast consisting of marble, which was raised 20 cm.

[32] According to the Earth Applied Sciences Disasters Program of NASA, synthetic-aperture radar data revealed Samos Island was raised by as much as 10 cm (3.9 in) meanwhile its northern coast subsided by the same amount.

The cracked caused part of the road, and small trees to slide several centimeters closer to the shore as a result of lateral spreading.

[22] Multiple social media posts showed water rushing through streets and ports in the region following the earthquake, along with tsunami warnings being issued for the islands of Ikaria, Kos, Chios and Samos.

[37][38] In Alaçatı on the Çeşme Peninsula, the tsunami flowed up a stream and inundated inland by as much as 2.49 km (1.55 mi).

Analysis of video footage on the coast showed that the tsunami had a maximum height of 1.7 m (5 ft 7 in) when it struck.

[31] East of Alaçatı, in Zeytineli, the tsunami severely damaged unoccupied resort houses along a stretch of beach.

The tsunami waves where higher in this region due to the presence of a shallow bay which altered the coastal geometry.

Shops, hotel lobbies, restaurants, offices and homes suffered slight damage when the tsunami inundated the ground level and indoors.

A maximum run-up height of 3.35 m (11.0 ft) was measured on the northern coast of Samos about 5.8 km (3.6 mi) east of Karlovasi Port.

Most of the damage and casualties were from the Bornova and Bayraklı districts of İzmir; located at least 70 km (43 mi) north of the epicentre.

[34] On-site investigations by the Turkish Ministry of Environment and Urbanization revised the number of collapsed and intentionally demolished buildings to 103.

The observation of damage effects and instrumental data found that ground motions were amplified 2.5–3 times in the İzmir basin.

[49] Greek authorities from Samos stated that although buildings were damaged across the island, the worst sustained was in Karlovasi,[51] where a large church had partially collapsed.

[54] Immediately after the earthquake, Turkish Minister of Health Fahrettin Koca stated that about 40 ambulances, 35 emergency rescue teams and two ambulance helicopters had reached the affected region,[55] while Turkey's Ministry of National Defence stated that one of its planes had departed from Etimesgut Air Base to transport AFAD and gendarmerie teams to the scene.

[56] The Turkish Red Crescent immediately deployed teams from six cities to provide food to those affected by the earthquake.

[59][60] A total of 17 collapsed buildings were part of the search and rescue operations, according to Mehmet Gulluoglu, head of Turkey's Disaster and Emergency Management Presidency (AFAD).

An investigation by the İzmir Chief Public Prosecutor's Office found that poor construction materials and practices, and the lack of inspections led to its collapse.

Seven of the nine workspaces in the first floor were combined, which meant columns were deliberately cut to make space for the supermarket.

Two of the accused were detained by authorities for "causing the death and injury of more than one person by conscious negligence", and could face jail time of up to 20 years.