1169 Sicily earthquake

1169 Sicily earthquake
Date February 4, 1169 (1169-02-04)
Origin time 07:00
Magnitude 7.3 Ms[1]
Epicenter 37°13′01″N 14°57′00″E / 37.217°N 14.95°E / 37.217; 14.95Coordinates: 37°13′01″N 14°57′00″E / 37.217°N 14.95°E / 37.217; 14.95[2]
Areas affected Eastern Sicily
Max. intensity X (Extreme)
Tsunami Yes
Casualties 15,000–25,000 deaths

The 1169 Sicily earthquake occurred on 4 February, in the year 1169, at 07:00 on the eve of the feast of St. Agatha of Sicily (in southern Italy). It had an estimated magnitude of between 6.4 and 7.3 and an estimated maximum perceived intensity of X (Extreme) on the Mercalli intensity scale. Catania, Lentini and Modica were severely damaged. It triggered a tsunami. Overall, the earthquake is estimated to have caused the deaths of at least 15,000 people.

Tectonic setting

Main faults of the Siculo-Calabrian rift zone

Sicily's considerable seismic activity is a product of plate tectonics: the island lies on part of the complex convergent boundary where the African Plate is subducting beneath the Eurasian Plate. This subduction zone is responsible for the formation of the stratovolcano Mount Etna. Most of the damaging earthquakes occur on the Siculo-Calabrian rift zone, a zone of extensional faulting which runs for about 370 kilometres (230 mi), forming three main segments through Calabria, along the east coast of Sicily and immediately offshore, and finally forming the southeastern margin of the Hyblean Plateau. Faults in the Calabrian segment were responsible for the 1783 Calabrian earthquakes sequence.[3]

In the southern part of the eastern coast of Sicily, investigations have identified a series of active normal dip-slip faults, dipping to the east. Most of these lie offshore, and some control basins that contain large thicknesses of Quaternary sediments. The two largest faults, known as the western and eastern master faults, border half-grabens, with fill of up to 700 metres (2,297 ft) and 800 metres (2,625 ft) respectively. Onshore, two ages of faulting have been recognised, an earlier phase trending NW-SE and a later phase trending SSW-NNE that clearly offsets the first group, including the Avola fault and the Rosolini-Ispica fault system.[4]

Earthquake

The location of the earthquake's epicentre is quite uncertain, with different seismologists giving locations offshore and onshore; there is similar uncertainty regarding the 1693 Sicily earthquake. The damaged area is similar to that for the 1693 earthquake, suggesting that both the location and magnitude were similar.[1] Intensities of X (Extreme) have been estimated for Catania, Lentini and Modica, IX (Violent) at Syracuse and Piazza Armerina and VIII (Severe) at Santi Pietro e Paolo and Messina. The earthquake was also felt in Calabria with a maximum intensity of VI (Strong) in Reggio Calabria.[2]

The magnitude of the earthquake has been estimated from intensity information and these estimates vary from 6.4 on the Me (Energy magnitude scale)[2] to 7.3 on the surface wave magnitude scale.[1]

Tsunami

The tsunami affected most of the Ionian coast of Sicily and caused inundation from Messina in the north to the mouth of the Simeto River in the south.[5]

Tsunami deposits correlated with this earthquake have been found both onshore[6] and offshore.[7] The tsunami is also thought to be responsible for moving several large boulders from the middle of the sublittoral zone onto the coast between Augusta and Syracuse.[8]

Eruption of Etna

Some accounts of this earthquake refer to a major eruption from Etna at the time of the earthquake, blaming most of the deaths in Catania and the tsunami on the eruption. However, most later workers believe that the tsunami was triggered by the earthquake and that the only effect on Etna was the collapse of part of the cone above Taormina, with no significant eruption.[9] As with the 1693 earthquake the 1169 event seems to have followed after a major period of eruptive activity.[10] Calculations have shown that a major eruption may significantly increase the stress on the normal faults to the south-east of the volcano.[11]

Damage

Catania was almost completely destroyed. The Cathedral collapsed killing the Bishop John of Ajello, 44 of the Benedictine monks, and many others who were crowded into the building for the feast of St. Agatha.[12] Great damage was also caused to Lentini, Modica, Aci Castello, Sortino and Syracuse.[1]

In a contemporary account Hugo Falcandus described the effects on the Arethusa spring in Syracuse, which increased its rate of flow greatly and became salty. Near Casale Saraceno the flow of another spring, known as Tais, stopped after the earthquake. Two hours later it returned with much greater force than before and had the colour of blood.[13]

Estimates of the death toll in the earthquake vary, with 15,000 being often quoted, sometimes for the overall total[14] and sometimes just for Catania.[13] A few sources give the higher estimate of 25,000.[15]

Aftermath

In the chaos that followed the earthquake, there was concern that exiles like Tancred of Lecce and Robert of Loritello would take part in a Byzantine invasion of the island. However, these disaffected exiles were soon allowed to return and there was no invasion, nor the rebellion that it might have triggered.[16]

Peter of Blois saw the earthquake as God's punishment on the Sicilians for the exile of Stephen du Perche and the appointment of Bishop John of Ajello, through bribery, to the see of Catania, replacing his brother William of Blois in the post.[17]

References

  1. 1 2 3 4 Azzaro, R.; Barbano M.S. (2000). "Analysis of the seismicity of Southeastern Sicily: a proposed tectonic interpretation". Annali di Geofisica 43 (1): 171–188. Viewed 25 June 2012.
  2. 1 2 3 Guidoboni, E.; Ferrari G., Mariotti D., Comastri A., Tarabusi G. and Valensise G. "Catalogue of Strong Earthquakes in Italy (461 BC – 1997) and Mediterranean Area (760 B.C. – 1500)". INGV-SGA. Retrieved 24 June 2012.
  3. ↑ Catalano, S.; De Guidi G., Monaco C., Tortorici G. & Tortorici L. (2008). "Active faulting and seismicity along the Siculo–Calabrian Rift Zone (Southern Italy)". Tectonophysics (Elsevier) 453 (1-4): 177–192. Bibcode:2008Tectp.453..177C. doi:10.1016/j.tecto.2007.05.008. Retrieved 24 June 2012.
  4. ↑ Bianca, M.; Monaco C., Tortorici L. & Cernobori L. (1999). "Quaternary normal faulting in southeastern Sicily (Italy): a seismic source for the 1693 large earthquake" (PDF). Geophysical Journal International (London: Royal Astronomical Society) 139: 370–394. Bibcode:1999GeoJI.139..370B. doi:10.1046/j.1365-246X.1999.00942.x. Retrieved 24 June 2012.
  5. ↑ De Martini, P.M.; Barbano M.S., Smedile A., Gerardi F., Pantosti D., Del Carlo P. & Pirrotta C. (2010). "A unique 4000 yrs long geological record of multiple tsunami inundations in the Augusta Bay (eastern Sicily, Italy)" (PDF). Marine Geology (Elsevier) 276 (1-4): 42–57. doi:10.1016/j.margeo.2010.07.005. Retrieved 24 June 2012.
  6. ↑ Scicchitano, G.; Costa B., Di Stefano A., Longhitano S. & Monaco C. (2008). "Tsunami deposits in the Siracusa coastal area (south-eastern Sicily)" (PDF). Rend. online SGI Note Brevi (Società Geologica Italiana) 1: 159–162. Retrieved 24 June 2012.
  7. ↑ Smedile, A.; De Martini P.M., Pantosti D., Bellucci L., Del Carlo P., Gasperini L., Pirrotta C., Polonia A. & Boschi E. (2011). "Possible tsunami signatures from an integrated study in the Augusta Bay offshore (Eastern Sicily—Italy)". Marine Geology (Elsevier) 281 (1-4): 1–13. doi:10.1016/j.margeo.2011.01.002. Retrieved 24 June 2012.
  8. ↑ Scicchitano, G.; Monaco C. & Tortorici L. (2007). "Large boulder deposits by tsunami waves along the Ionian coast of south-eastern Sicily (Italy)". Marine Geology (Elsevier) 238 (1-4): 75–91. doi:10.1016/j.margeo.2006.12.005. Retrieved 24 June 2012.
  9. ↑ Tinti, S. (1993). Tsunamis in the World. Advances in Natural and Technological Hazards Research 1. Springer. p. 57. ISBN 9780792323167.
  10. ↑ Hirn, A.; Nicolich R., Gallart J., Laigle M., Cernobori L. & ETNASEIS Scientific Group (1997). "Roots of Etna volcano in faults of great earthquakes" (PDF). Earth and Planetary Science Letters (Elsevier) 148: 171–191. Bibcode:1997E&PSL.148..171H. doi:10.1016/S0012-821X(97)00023-X. Retrieved 24 June 2012.
  11. ↑ Feuillet, N.; Cocco M., Musumeci C. & Nostro C. (2006). "Stress interaction between seismic and volcanic activity at Mt Etna" (PDF). Geophysical Journal International (London: Royal Astronomical Society) 164: 697–718. Bibcode:2006GeoJI.164..697F. doi:10.1111/j.1365-246X.2005.02824.x. Retrieved 24 June 2012.
  12. ↑ White, L.T. (1938). Latin Monasticism in Norman Sicily. The Mediaeval academy of America 31. Mediaeval Academy of America. p. 115.
  13. 1 2 Falcando, Ugo (1998). Loud G.A. & Wiedmann T.E.J., ed. The History of the Tyrants of Sicily by "Hugo Falcandus," 1154-69. Manchester University Press. pp. 216–217. ISBN 9780719054358. Retrieved 25 June 2012.
  14. ↑ Solov'ev, S.L. (2000). Tsunamis in the Mediterranean Sea, 2000 B.C.-2000 A.D. Advances in Natural and Technological Hazards Research 13. Springer. p. 36. Retrieved 25 June 2012.
  15. ↑ Barbano, M.S.; De Martini P.M., Pantosti D., Smedile A., Del Carlo P., Gerardi F., Guarnieri P. & Pirrotta C. (2011). "In search of Tsunami deposits along the eastern coast of Sicily (Italy): state of the art". In Guarnieri P. Recent Progress on Earthquake Geology (PDF). Nova. pp. 109–146. ISBN 978-1-60876-147-0. Retrieved 25 June 2012.
  16. ↑ Metcalfe, A. (2009). The Muslims of Medieval Italy. Edinburgh University Press. p. 205. ISBN 9780748620081. Retrieved 25 June 2012.
  17. ↑ Peter of Blois; Loud G.A. (translator). "Some Letters of Peter of Blois concerning Sicily" (PDF). pp. 4–6. Retrieved 25 June 2012.
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