The 2021 Lasithi earthquake was a magnitude 6.4 earthquake with a maximum intensity of VIII (''Severe'') on the

Modified Mercalli Intensity Scale The Modified Mercalli intensity scale (MM, MMI, or MCS), developed from Giuseppe Mercalli's Mercalli intensity scale of 1902, is a seismic intensity scale used for measuring the intensity of shaking produced by an earthquake. It measures the eff ...

which occurred on October 12, 2021, 12:24 ( UTC+3:30) off the island of

Crete Crete ( el, Κρήτη, translit=, Modern: , Ancient: ) is the largest and most populous of the Greek islands, the 88th largest island in the world and the fifth largest island in the Mediterranean Sea, after Sicily, Sardinia, Cyprus, ...

. The quake was also felt at low intensity as far as

Cairo Cairo ( ; ar, القاهرة, al-Qāhirah, ) is the Capital city, capital of Egypt and its largest city, home to 10 million people. It is also part of the List of urban agglomerations in Africa, largest urban agglomeration in Africa, List of ...

and

Istanbul ) , postal_code_type = Postal code , postal_code = 34000 to 34990 , area_code = +90 212 (European side) +90 216 (Asian side) , registration_plate = 34 , blank_name_sec2 = GeoTLD , blank_i ...

. The quake occurred on the anniversary of the

1856 Heraklion earthquake The 1856 Heraklion earthquake, also known as the Crete earthquake or Rhodes earthquake occurred on the morning of October 12 at 02:45 am local time. This extremely catastrophic earthquake had an estimated magnitude of 7.7 to 8.3 at a depth of appr ...

which killed about 600 people and about two weeks after the

2021 Arkalochori earthquake A moment magnitude 6.0 earthquake struck the island of Crete in Greece at a depth of 6 km on 27 September 2021. The epicenter of the earthquake was located southeast of Heraklion. The quake killed one person, injured 36 (one indirect) and dam ...

. Weak tremors were felt in Giza and

, which also coincided with the anniversary of the

1992 Cairo earthquake The 1992 Cairo Earthquake, also known as the 1992 Dahshur earthquake, occurred at 15:09 local time (13:09 UTC) on 12 October, with an epicenter in the Western Desert near Dahshur, Giza, south of Egypt's capital and most populous city, Cairo. T ...

. The tremor was the largest earthquake in Greece since the 2020 Aegean Sea earthquake.

Earthquake

The quake was recorded as a 6.3 earthquake by the

European-Mediterranean Seismological Centre The European-Mediterranean Seismological Centre (EMSC; french: Centre Sismologique Euro-Méditerranéen, ) is an international, non-governmental and not-for-profit organisation. The European-Mediterranean region is prone to destructive earthquak ...

, but was upgraded to 6.4 in magnitude. Efthymios Lekkas, president of the Earthquake Planning and Protection Organisation, said that the quake was not directly related to the first tremor a month ago, but instead was a sign of the activation of the Eastern part of the Hellenic arc. According to a moment tensor solution by the

U.S. Geological Survey The United States Geological Survey (USGS), formerly simply known as the Geological Survey, is a scientific agency of the United States government. The scientists of the USGS study the landscape of the United States, its natural resources, and ...

, the earthquake was associated with shallow

normal fault In geology, a fault is a planar fracture or discontinuity in a volume of rock across which there has been significant displacement as a result of rock-mass movements. Large faults within Earth's crust result from the action of plate tecton ...

ing within the Aegean Sea Plate at a depth of 10 km. Due to the distance between the 6.4 and 6.0 events, spaced far apart, it is not likely they are directedly related. Greek

seismologists Seismology (; from Ancient Greek σεισμός (''seismós'') meaning "earthquake" and -λογία (''-logía'') meaning "study of") is the scientific study of earthquakes and the propagation of elastic waves through the Earth or through other ...

added that the two earthquakes occurred by chance despite saying that the chances of two large events happening in the same region is low. The lack of aftershocks sparked concern among seismologists due to the lack of aftershocks following the quake. The rate of aftershocks were substantially lower than expected for an earthquake of its size.

Tectonic setting

The island of Crete, and the country of Greece in general is prone to seismic activity and is home to one of the most destructive earthquakes in all of Europe. Crete lies in the non-magmatic part of the so-called

Hellenic arc The Hellenic arc or Aegean arc is an arcuate mountain chain of the southern Aegean Sea located on the southern margin of the Aegean Sea Plate. Geologically it results from the subduction of the African Plate under it along the Hellenic subductio ...

which is related to of the subduction of the

African Plate The African Plate is a major tectonic plate that includes much of the continent of Africa (except for its easternmost part) and the adjacent oceanic crust to the west and south. It is bounded by the North American Plate and South American Plate ...

beneath the

Eurasian Plate The Eurasian Plate is a tectonic plate that includes most of the continent of Eurasia (a landmass consisting of the traditional continents of Europe and Asia), with the notable exceptions of the Indian subcontinent, the Arabian subcontinent and ...

(specifically the

Aegean Sea plate The Aegean Sea Plate (also called the Hellenic Plate or Aegean Plate) is a small tectonic plate located in the eastern Mediterranean Sea under southern Greece and western Turkey. Its southern edge is the Hellenic subduction zone south of Crete, ...

). Crete is affected by large earthquakes originating from or near the subduction zone, such as the

365 Crete earthquake The 365 Crete earthquake occurred at about sunrise on 21 July 365 in the Eastern Mediterranean, with an assumed epicentre near Crete. Geologists today estimate the undersea earthquake to have been a moment magnitude 8.5 or higher. It caused wid ...

. It is also affected by much shallower earthquakes resulting from ongoing

extension Extension, extend or extended may refer to: Mathematics Logic or set theory * Axiom of extensionality * Extensible cardinal * Extension (model theory) * Extension (predicate logic), the set of tuples of values that satisfy the predicate * E ...

orientated north–south (on west–east trending normal faults) and west–east (on south–north to SSW–NNE trending normal faults).

Damage

According to the Mayor of

Sitia Sitia ( el, Σητεία) is a port town and a municipality in Lasithi, Crete, Greece. The town has 9,912 inhabitants (2011) and the municipality has 18,318 (2011). It lies east of Agios Nikolaos and northeast of Ierapetra. Sitia port is on the ...

, the town hall was confirmed to have sustained damage. The church of Saint Nicholas in Xerokampos, Sitia collapsed, but no casualties were reported as the structure was vacant during the time of the shock. Efthymios Lekkas, a professor of dynamic tectonic applied geology & disaster management at the National and Kapodistrian University of Athens said that fortunately damage was minimal and was only observed in old or abandoned masonry buildings. At Xerokampos, the quake knocked off items off shelves at shops. The town hall building of According to the Mayor of

, the town hall of was confirmed to have sustained damage. The church of Saint Nicholas in Xerokampos, Sitia collapsed, but no casualties were reported as the structure was vacant during the time of the shock. Efthymios Lekkas, a professor of dynamic tectonic applied geology & disaster management at the National and Kapodistrian University of Athens said that damage was minimal and was only observed in old or abandoned masonry buildings. At Xerokampos, the quake knocked off items off shelves at shops. The town hall building of

suffered minor fracturing on the facade.

Tsunami

A small

tsunami A tsunami ( ; from ja, 津波, lit=harbour wave, ) is a series of waves in a water body caused by the displacement of a large volume of water, generally in an ocean or a large lake. Earthquakes, volcanic eruptions and other underwater exp ...

was detected by instruments in the sea, prompting coastal residents to stay away from the sea. OASP President Efthymios Lekkas said in a statement: "''We have issued a tsunami alert but nothing alarming. We are talking about 10 kilometers southeast of Zakros. The phenomenon has arrived and may not be visible in some areas. The quake was small to create a large tsunami. Apart from Crete, the whole southern Aegean'' has ''been shaken,"'' Geodynamics Institute in Athens director Vassilis Karastathis also said in an interview with popular Greek newspaper

Proto Thema Proto or PROTO may refer to: Language * Proto-, an English prefix meaning "first" Media * ''Proto'' (magazine), an American science magazine *Radio Proto in Cyprus Music * ''Proto'' (Holly Herndon album), 2019 * ''Proto'' (Leo O'Kelly ...

saying: ''"There is always an announcement when there is a strong earthquake in the sea. To understand what happens when we have a strong seismic event at sea because we are dealing with time in relation to the tsunami we do not wait for time to pass and until we see all the data from the warning systems we send the announcement for good and for bad. So depending on some rules of earthquake magnitude and distance from the shores and of course to be in the sea then we issue a warning. So here, since it is not on land and it was at sea, we made the announcement ".''

Response

Stavros Arnaoutakis, the Governor of Crete calmed the people, saying ''"We have to be cool, so far I have no reports of injuries."'' He also said in an interview with Greek newspaper Proto Thema: "We were rocking for 15 seconds." The municipality of Malevezi has issued the cancellations of schools and kindergartens. The further inspection of damaged infrastructure and irrigation networks were also observed in the Municipality. The earthquake management team which was already present since September 27 after the initial quake a month earlier was re-implemented as well as the return of the mobilization of the Civil Protection in the municipality.

References