1703 Apennine earthquakes

1703 Apennine earthquakes
14 January
16 January
2 February
Date 14 January 1703 (1703-01-14)
Magnitude 6.7-6.2-6.7 Magnitude Richter
Epicenter 42°42′N 13°04′E / 42.7°N 13.07°E / 42.7; 13.07
(first earthquake in sequence)
Areas affected Italy

The 1703 Apennine earthquakes were a sequence of three earthquakes of magnitude ≥6 that occurred in the central Apennines of Italy, over a period of 19 days. The epicenters were near Norcia (14 January), Montereale (16 January) and L'Aquila (2 February), showing a southwards progression over about 36 km. These events involved all of the known active faults between Norcia and L'Aquila.[1] A total of about 10,000 people are estimated to have died as a result of these earthquakes,[2] although because of the overlap in areas affected by the three events, casualty numbers remain highly uncertain.

Tectonic setting

The central part of the Apennines has been characterised by extensional tectonics since the Pliocene epoch (i.e. about the last 5 million years), with most of the active faults being normal in type and NW-SE trending.[3] The extension is due to the back-arc basin in the Tyrrhenian Sea opening faster than the African Plate is colliding with the Eurasian Plate.[4]

The Norcia earthquake

The earthquake occurred at 18:00 UTC on 14 January with an estimated magnitude of 6.7.[5] It was caused by movement on an en echelon set of three normal faults, known as the Norcia Fault System.[1]

Damage

There was extensive damage in the area around Norcia, with Spoleto and Rieti also affected.[6] Modern estimates give a maximum intensity of XI (Very Disastrous).[7] Ground rupture was observed at several locations and these have been confirmed by modern investigations.[1]

Casualties

Estimates of the death toll vary from 6,240[8] to 9,761.[5]

The Montereale earthquake

The earthquake occurred at 13:30 UTC on 16 January with an estimated magnitude of 6.2.[5] It is thought to have been caused by movement on the Montereale Fault.[1] Damage was recorded in Montereale, Cittareale, Accumoli and Amatrice. Although of lower magnitude than the other two events, this earthquake was still felt in Rome.[6] The estimated intensity for this event is VIII (Destructive).[7] No separate casualty figures are available for this event.

The L'Aquila earthquake

The earthquake occurred at 11:05 UTC on 2 February with an estimated magnitude of 6.7.[5] It was caused by movement on the Mt. Marine Fault.[1]

Damage

Most of the buildings in L’Aquila were badly damaged or completely destroyed. Damage was reported from as far away as Rome.[6] Modern estimates give a maximum intensity of X (Disastrous).[7] The earthquake caused a huge landslide on the Mt. Marine ridge, a large slope failure near Posta and liquefaction along the Aterno River.

Casualties

Estimates of the death toll vary from 2,500[7] to 5,000.[9]

Summary of earthquakes

Name Date Time Coordinates Magnitude Intensity
Norcia 14 January 18:00 42°42′N 13°04′E / 42.70°N 13.07°E / 42.70; 13.07Coordinates: 42°42′N 13°04′E / 42.70°N 13.07°E / 42.70; 13.07 6.7 XI
Montereale 16 January 13:30 42°37′N 13°06′E / 42.62°N 13.10°E / 42.62; 13.10 6.2 VIII
L'Aquila 2 February 11:05 42°26′N 13°18′E / 42.43°N 13.30°E / 42.43; 13.30 6.7 X

Relationship between the events

Some seismologists interpret these events as related. It has been suggested that the Norcia earthquake led directly to the Montereale event, which had the effect of further loading the fault at Aquila, thus triggering the final event.[1] Such sequential adjacent events are examples of Coulomb stress transfer.

See also

References

  1. 1 2 3 4 5 6 Galli, P., Galadini, F. & Calzoni, F. (2005). "Surface faulting in Norcia (central Italy): a "paleoseismological perspective". Tectonophysics 403: 117–130. doi:10.1016/j.tecto.2005.04.003.
  2. ↑ "Seismically Induced Ground Ruptures and Large Scale Mass Movements: Field Excursion and Meeting 21-27 september 2001" (PDF). Archived from the original on 27 September 2009. Retrieved 25 September 2009.
  3. ↑ "Effect of Time Dependence on Probabilistic Seismic-Hazard Maps and Deaggregation for the Central Apennines, Italy". Seismological Society of America. 6 April 2009. Archived from the original on 29 July 2009. Retrieved 6 April 2009.
  4. ↑ "Magnitude 6.3 - CENTRAL ITALY 2009 April 06 01:32:42 UTC". USGS. 6 April 2009. Archived from the original on 9 April 2009. Retrieved 6 April 2009.
  5. 1 2 3 4 "IISEENET (Information Network of Earthquake disaster Prevention Technologies) - Search Page". Archived from the original on 27 September 2009. Retrieved 25 September 2009.
  6. 1 2 3 "Description of the effects in Rome caused by the three earthquakes". Legacy.ingv.it. Retrieved 2012-05-21.
  7. 1 2 3 4 "Geological effects induced by the L’Aquila earthquake (6 April 2009, Ml = 5.8) on the natural environment: preliminary report" (PDF). Retrieved 2012-05-21.
  8. ↑ "Davison, C. 1912-1913. The death-rate of earthquakes, Science progress in the twentieth century, A quarterly journal of Scientific work & thought". Archive.org. Retrieved 2012-05-21.
  9. ↑ Buffon, Georges Louis Leclerc (1792). Buffon's Natural History 2. London: J.S. Barr. OCLC 316760617.
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