The 1963 Marj earthquake occurred on February 21 in northern

Libya Libya (; ar, ليبيا, Lībiyā), officially the State of Libya ( ar, دولة ليبيا, Dawlat Lībiyā), is a country in the Maghreb region in North Africa. It is bordered by the Mediterranean Sea to the north, Egypt to Egypt–Libya bo ...

. The earthquake occurred at with a

moment magnitude The moment magnitude scale (MMS; denoted explicitly with or Mw, and generally implied with use of a single M for magnitude) is a measure of an earthquake's magnitude ("size" or strength) based on its seismic moment. It was defined in a 1979 pape ...

of 5.6 and a maximum Mercalli intensity of VIII (''Severe''). Financial losses totaled $5 million USD, with 290–375 deaths, 375–500 injuries, and 12,000 homeless.

Tectonic setting

The northern part of

Cyrenaica Cyrenaica ( ) or Kyrenaika ( ar, برقة, Barqah, grc-koi, Κυρηναϊκή ��παρχίαKurēnaïkḗ parkhíā}, after the city of Cyrene), is the eastern region of Libya. Cyrenaica includes all of the eastern part of Libya between ...

lies close to the northern edge 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 Plat ...

. Offshore lies the

Mediterranean Ridge The Mediterranean Ridge is a wide ridge in the bed of the Mediterranean Sea, running along a rough quarter circle from Calabria, south of Crete, to the southwest corner of Turkey. It is an accretionary wedge caused by the African Plate subductin ...

, an

accretionary wedge An accretionary wedge or accretionary prism forms from sediments accreted onto the non-subducting tectonic plate at a convergent plate boundary. Most of the material in the accretionary wedge consists of marine sediments scraped off from the do ...

, developed above the destructive plate boundary where the African Plate is being

subducted Subduction is a geological process in which the oceanic lithosphere is recycled into the Earth's mantle at convergent boundaries. Where the oceanic lithosphere of a tectonic plate converges with the less dense lithosphere of a second plate, the ...

beneath 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, ...

along the

Hellenic subduction zone The Hellenic subduction zone (HSZ) is the convergent boundary between the African Plate and the Aegean Sea Plate, where oceanic crust of the African is being subducted north–northeastwards beneath the Aegean. The southernmost and shallowest part ...

. The Cyrenaica promontory is thought to be undergoing incipient

collision In physics, a collision is any event in which two or more bodies exert forces on each other in a relatively short time. Although the most common use of the word ''collision'' refers to incidents in which two or more objects collide with great fo ...

as the

continental margin A continental margin is the outer edge of continental crust abutting oceanic crust under coastal waters. It is one of the three major zones of the ocean floor, the other two being deep-ocean basins and mid-ocean ridges. The continental margin ...

enters the subduction zone. The Cyrenaica region is characterised by relatively low magnitude earthquakes with

thrust fault A thrust fault is a break in the Earth's crust, across which older rocks are pushed above younger rocks. Thrust geometry and nomenclature Reverse faults A thrust fault is a type of reverse fault that has a dip of 45 degrees or less. If ...

focal mechanism The focal mechanism of an earthquake describes the deformation in the source region that generates the seismic waves. In the case of a fault-related event it refers to the orientation of the fault plane that slipped and the slip vector and is ...

s, developed in a area of NE–SW directed maximum horizontal

stress Stress may refer to: Science and medicine * Stress (biology), an organism's response to a stressor such as an environmental condition * Stress (linguistics), relative emphasis or prominence given to a syllable in a word, or to a word in a phrase ...

Earthquake

The earthquake's epicenter is located about 13 km to the north-northeast of the city of Marj in the

Marj District Marj ( ar, المرج ', en, The Meadows) is an administrative division (''shabiyah'' or district) of northeastern Libya, lying on the Mediterranean Sea coast. Its administrative seat is the city of Marj, which was formerly known as Barca. M ...

of Cyrenaica. It was felt as far away as

Benghazi Benghazi () , ; it, Bengasi; tr, Bingazi; ber, Bernîk, script=Latn; also: ''Bengasi'', ''Benghasi'', ''Banghāzī'', ''Binghāzī'', ''Bengazi''; grc, Βερενίκη (''Berenice'') and ''Hesperides''., group=note (''lit. Son of he Ghazi ...

, about 100 km from the epicenter. The magnitude has been calculated as 5.6 by the

ISC #REDIRECT ISC {{redirect category shell, {{R from other capitalisation{{R from ambiguous page ...

. It was followed later that day by two

aftershock In seismology, an aftershock is a smaller earthquake that follows a larger earthquake, in the same area of the main shock, caused as the displaced crust adjusts to the effects of the main shock. Large earthquakes can have hundreds to thousand ...

s of over 4.0.

Damage

The main area of damage was restricted to a 20 km long section of the

alluvial plain An alluvial plain is a largely flat landform created by the deposition of sediment over a long period of time by one or more rivers coming from highland regions, from which alluvial soil forms. A floodplain is part of the process, being the sma ...

around Marj, which is located between two escarpments, possibly fault-related. The maximum damage was observed at Maddalena, a village about 12 km from Marj and close to the epicenter, in which all the farmhouses collapsed. The effects of the shaking depended on the construction type of the buildings. Those built of

rubble masonry Rubble stone is rough, uneven building stone not laid in regular courses. It may fill the core of a wall which is faced with unit masonry such as brick or ashlar. Analogously, some medieval cathedral walls are outer shells of ashlar with an inn ...

were most affected, with many collapsing and causing most of the casualties. Buildings constructed from hollow concrete blocks were only moderately affected and those built with reinforced concrete were almost completely unaffected.

Aftermath

The Libyan authorities followed the recommendations of the UNESCO report and rebuilt Marj on firmer ground about 4 km away from its original location.

References

External links