2017 Aegean Sea earthquake

2017 Bodrum–Kos earthquake
	A damaged bar in Kos
UTC time	2017-07-20 22:31:11
ISC event	610790782
USGS-ANSS	ComCat
Local date	21 July 2017
Local time	01:31 (EEST) (UTC+03.00)
Magnitude	6.6 Mw
Depth	7.0 km (4.3 mi)
Epicenter	36°55′23″N 27°24′54″E / 36.923°N 27.415°E
Type	Normal faulting
Areas affected	Greece ; Turkey
Max. intensity	MMI VII (Very strong)
Tsunami	Up to 1.9 m (6.2 ft) along the Greek and Turkish coasts
Aftershocks	390 aftershocks (M > 3.0) in 1 year, the highest being a Mw(KOERI)  5.3
Casualties	2 killed, 480 injured

On 21 July 2017, a large earthquake measuring 6.6 on the moment magnitude scale struck right near Bodrum, a popular town of tourism in Turkey, killing 2 and injuring hundreds. Mostly referenced as the 2017 Bodrum–Kos earthquake, this earthquake generated a tsunami which was one of the largest tsunamis in the Mediterranean Sea region.

Tectonic setting

Seismotectonic map of the Gulf of Gökova. The red star marks the epicenter of the 2017 earthquake.

The Eastern Mediterranean where the earthquake occurred is an area of complex tectonics related to the collision of the Eurasian plate, African plate and Arabian plate. Continental collision occur here, including subduction of the African plate lithosphere under the Eurasian plate (specifically, the Aegean Plate and the Anatolian Plate); the transform boundary between the African plate and Arabian plate which forms the Dead Sea Transform; and the convergent boundary separating the Aegean and Anatolian Plate.^[1]

The Aegean region, is a seismically and volcanically active area that has been deformed under a north-to-south extensional tectonic regime at up to 30-40 mm/yr since the Pliocene. Where the epicenter of the earthquake is located, the Gulf of Gökova is an east–west trending asymmetric graben measuring 120 km (75 mi) long and 5–30 km (3–19 mi) wide. It developed on nappes which are filled with Pliocene to Quaternary marine sediments. The depression is bordered by the Datça Peninsula to the south, Kos to the west, and the Bodrum Peninsula to the north. The northern part of the graben is dominated by the Gökova Fault Zone which is one of the most seismically active fault structures in southwestern Anatolia. It is an east–west and northeast–southwest trending arc-shaped fault zone.^[2] The Gökova Fault Zone contains a complex fault pattern which could be related to the interaction between deep strike-slip faults and shallower normal faults. According to observed geological markers, the combined offset of the fault zone is about 1,000 m (3,281 ft) since the Pliocene period. This suggests a slip rate of around 0.2 mm/yr.^[3] Most faults in the fault zone are underwater while some are visible on land.^[4]

Past seismicity

In historical times, many large earthquakes have struck the Gökova associated with the fault zone. Historical earthquakes with a record of damage include 412 BC, 227 BC, 199–198 BC, 24 BC, 141 AD, 174 AD, 344 AD, 474 AD, 554 AD, 1493 AD, 1851 AD, 1863 AD and 1869 AD events. In the 1493 event, the city of Bodrum was totally destroyed.^[5] In the 20th century, large instrumentally recorded events (events recorded by seismometers or other instruments) include those of 1933 and 1941 with magnitudes of 6.4 and 6.0 respectively.^[6]

Earthquake

Distribution of the slip along the fault (top) and intensity map (bottom)

The M_w 6.6 earthquake struck at 01:31 on 21 July 2017 at a depth of 7 km. It caused shaking assigned MMI VII (Very strong). Focal mechanism solutions of the earthquake indicate this event was generated by an east–west trending normal fault within the lithosphere within the Aegean Plate.^[7] Coulomb stress modeling showed the earthquake ruptured an area with around 16 km (10 mi) length and 11 km (7 mi) width on a west-southwest to east-northeast direction.^[8]

Deformation

Ground deformation and displacement of the mainshock faulting were observed via GPS and interferograms. Most of the deformation was observed in Karaada, near the epicenter.^[9]

Tsunami

Relative to the large magnitude and large depth, the earthquake generated a tsunami which was one of the largest ever recorded in the Mediterranean since records began in 426 BC.^[10] The tsunami was first picked up by a tide gauge in Bodrum, which measured 0.11 m (4 in). In the next few weeks after the main earthquake, field surveys were performed. As a result of the surveys, tsunami inundations as much as 100 m (328 ft) were observed with a run-up height of 1.9 m (6 ft). Many dead fish were found, cars were dragged and boats were damaged.^[11]

Damage

The Defterdar Mosque on Kos (pictured here in 2011) before...

...and after the earthquake.

Extensive damage took place on the island of Kos, and to a lesser degree in the area around Bodrum. On Kos, the old town was worst affected, with the cathedral, the 18th century Defterdar mosque, and a 14th-century castle being badly damaged. The main harbour had its floor crack as a result of the tremor, and was subsequently declared unsafe for use by government officials, who rerouted all ferries to the smaller port town of Kefalos in west Kos.^[12]

Two fatalities were reported on the island, in addition to more than 120 injuries.^[12] The two dead were identified as Turkish and Swedish nationals, and were killed when the upper facade of a bar collapsed on top of them.^[13] Seven seriously injured people on Kos were flown to hospitals in Athens and Heraklion, including two men from Sweden and Norway in critical condition. Around 360 people were injured in Bodrum, many after jumping out of windows in panic, but none of the injuries were regarded as serious.^[12]^[14]^[15]