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The 1968 Belice earthquake sequence took place in
Sicily Sicily (Italian language, Italian and ), officially the Sicilian Region (), is an island in the central Mediterranean Sea, south of the Italian Peninsula in continental Europe and is one of the 20 regions of Italy, regions of Italy. With 4. ...
between 14 and 15 January. The largest shock measured 5.5 on the
moment magnitude scale The moment magnitude scale (MMS; denoted explicitly with or Mwg, 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. was defined in a 1979 paper ...
, with five others of magnitude 5+. The maximum perceived intensity was X (''Extreme'') on the
Mercalli intensity scale The Modified Mercalli intensity scale (MM, MMI, or MCS) measures the effects of an earthquake at a given location. This is in contrast with the seismic magnitude usually reported for an earthquake. Magnitude scales measure the inherent force or ...
. The
earthquake An earthquakealso called a quake, tremor, or tembloris the shaking of the Earth's surface resulting from a sudden release of energy in the lithosphere that creates seismic waves. Earthquakes can range in intensity, from those so weak they ...
sequence, centred between the towns of Gibellina, Salaparuta and Poggioreale, killed at least 231 people, possibly more than 400, with between 632 and about 1,000 injured and left 100,000 homeless. It is known in Italy as Terremoto del Belice.


Tectonic setting

Sicily lies on the complex
convergent plate boundary A convergent boundary (also known as a destructive boundary) is an area on Earth where two or more lithospheric plates collide. One plate eventually slides beneath the other, a process known as subduction. The subduction zone can be defined by a ...
between the African plate and the Eurasian plate. The geology of the western part of the island is dominated by the Gela Nappe, a thin-skinned
fold and thrust belt A fold and thrust belt is a series of mountainous foothills adjacent to an orogenic belt, which forms due to contractional tectonics. Fold and thrust belts commonly form in the forelands adjacent to major orogens as deformation propagates outwards ...
. The Gela Nappe consists of
Pliocene The Pliocene ( ; also Pleiocene) is the epoch (geology), epoch in the geologic time scale that extends from 5.33 to 2.58Quaternary The Quaternary ( ) is the current and most recent of the three periods of the Cenozoic Era in the geologic time scale of the International Commission on Stratigraphy (ICS), as well as the current and most recent of the twelve periods of the ...
age sedimentary rocks deposited in the earlier foredeep, thrust up onto the thick carbonate sequence of the Pelagian-Hyblean Platform of the African plate.


Earthquake

There was a sequence of six M 5+ earthquakes, making this western Sicily's largest historical seismic event, beginning with a M 5.2 shock at 12:28 on the 14 January, followed by a M 5.1 event at 13:15 on the same day and a M 5.2 event at 01:33 on 15 January, the mainshock at 02:01, and two M 5.2 events at 16:42 on 16 January and at 09:56 on 25 January. The greatest perceived intensity on the Mercalli scale was X (''Extreme'') at Gibellina, Montevago and Salaparuta. Intensities at Poggioreale, Santa Margherita di Belice, Santa Ninfa, Partanna and Salemi reached IX (''Violent'') on the scale. The
focal mechanism The focal mechanism of an earthquake describes the Fault (geology)#Slip.2C heave.2C throw, deformation in the Hypocenter, source region that generates the seismic waves. In the case of a Fault (geology), fault-related event, it refers to the ori ...
s of the mainshock and the two magnitude 5+ aftershocks are consistent with thrusting on faults trending west–east, although an alternative solution has been proposed for the mainshock of right lateral
transpression In geology, transpression is a type of Strike-slip fault, strike-slip deformation that deviates from simple shear because of a simultaneous component of shortening perpendicular to the fault plane. This movement ends up resulting in oblique shear. ...
on a NNW-SSE trending fault.


Damage

The main area of damage was centred on the valley of the Belice, with worst affected towns being Santa Ninfa,
Partanna Partanna is a town and ''comune'' in province of Trapani, south-western Sicily, southern Italy. It is south-east of Trapani Trapani ( ; ; ) is a city and municipality (''comune'') with 54,887 inhabitants, on the west coast of Sicily, in I ...
,
Montevago Montevago ( Sicilian: ''Muntivau'') is a ''comune'' (municipality) in the Province of Agrigento in the Italian region Sicily, located about southwest of Palermo and about northwest of Agrigento. Montevago borders the following municipalities: ...
, Santa Margherita di Belice, Gibellina, Salaparuta, Poggioreale. Vita, Salemi, and Camporeale also suffered significant damage. The earthquakes on 14 January did little damage, but many of the inhabitants spent the following night sleeping outside, during which the most damaging of the shocks occurred, which probably greatly reduced the number of casualties. The official death toll was 231 with a further 623 injured. Other estimates give more than 400 dead with over 1,000 injured. An estimated 100,000 people were made homeless by the earthquakes. The worst affected buildings were of unreinforced masonry construction that used irregular stones with weak mortar and had roofs consisting of heavy tiles resting on wooden beams. Such buildings collapsed completely in many cases. Houses with load-bearing walls made of regular stone or concrete blocks and better quality mortar performed better, although some were badly damaged. The most modern buildings that used reinforced concrete frames generally suffered little damage.


Aftermath

The immediate relief effort was hampered by a lack of disaster relief planning at both local and provincial levels, excessive bureaucracy, a lack of supplies close to the affected areas and a tendency of refugees to treat outsiders with suspicion. One year after the earthquakes, many hundreds of people were still living in tents and many of the prefabricated housing units had yet to appear, despite having been paid for; no work had begun on providing permanent housing. Two-thirds of refugee families had still not received their government grant. Nine years after the earthquake, none of the refugees had been placed in new housing, leaving 60,000 still living in temporary accommodation. The towns of Poggioreale, Gibellina, Vita, Santa Margherita di Belice and Salaparuta were eventually rebuilt in new locations.


See also

* List of earthquakes in 1968 *
List of earthquakes in Italy This is a list of earthquakes in Italy that had epicentres in Italy, or significantly affected the country. On average every four years an earthquake with a magnitude equal to or greater than 5.5 occurs in Italy. Due to the particular geodynam ...


References


Further reading

*


External links

* * {{DEFAULTSORT:Belice Earthquake, 1968 1968 Belice 1968 earthquakes 1968 in Italy
1968 Events January–February * January 1968, January – The I'm Backing Britain, I'm Backing Britain campaign starts spontaneously. * January 5 – Prague Spring: Alexander Dubček is chosen as leader of the Communist Party of Cze ...
January 1968 in Europe Earthquake clusters, swarms, and sequences 1960s disasters in Italy 1968 disasters in Europe