The 1703 Apennine earthquakes were a sequence of three

earthquake An earthquake (also known as a quake, tremor or temblor) is the shaking of the surface of the Earth resulting from a sudden release of energy in the Earth's lithosphere that creates seismic waves. Earthquakes can range in intensity, from ...

s of

magnitude Magnitude may refer to: Mathematics *Euclidean vector, a quantity defined by both its magnitude and its direction *Magnitude (mathematics), the relative size of an object *Norm (mathematics), a term for the size or length of a vector *Order of ...

≥6 that occurred in the central

Apennines The Apennines or Apennine Mountains (; grc-gre, links=no, Ἀπέννινα ὄρη or Ἀπέννινον ὄρος; la, Appenninus or – a singular with plural meaning;''Apenninus'' (Greek or ) has the form of an adjective, which wou ...

of Italy, over a period of 19 days. The

epicenter The epicenter, epicentre () or epicentrum in seismology is the point on the Earth's surface directly above a hypocenter or focus, the point where an earthquake or an underground explosion originates. Surface damage Before the instrumental pe ...

s were near

Norcia Norcia (), traditionally known in English by its Latin name of Nursia (), is a town and comune in the province of Perugia (Italy) in southeastern Umbria. Unlike many ancient towns, it is located in a wide plain abutting the Monti Sibillini, a su ...

(14 January), Montereale (16 January) and

L'Aquila L'Aquila ( , ) is a city and ''comune'' in central Italy. It is the capital city of both the Abruzzo region and of the Province of L'Aquila. , it has a population of 70,967 inhabitants. Laid out within medieval walls on a hill in the wide valle ...

(2 February), showing a southwards progression over about . These events involved all of the known active faults between Norcia and L'Aquila. A total of about 10,000 people are estimated to have died as a result of these earthquakes, 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 Extensional tectonics is concerned with the structures formed by, and the tectonic processes associated with, the stretching of a planetary body's crust or lithosphere. Deformation styles The types of structure and the geometries formed depend on ...

since the

Pliocene The Pliocene ( ; also Pleiocene) is the epoch in the geologic time scale that extends from 5.333 million to 2.58epoch In chronology and periodization, an epoch or reference epoch is an instant in time chosen as the origin of a particular calendar era. The "epoch" serves as a reference point from which time is measured. The moment of epoch is usually decided by ...

(i.e. about the last 5 million years), with most of the

active fault An active fault is a fault that is likely to become the source of another earthquake sometime in the future. Geologists commonly consider faults to be active if there has been movement observed or evidence of seismic activity during the last 10,0 ...

s being normal in type and NW-SE trending. The extension is due to the

back-arc basin A back-arc basin is a type of geologic basin, found at some convergent plate boundaries. Presently all back-arc basins are submarine features associated with island arcs and subduction zones, with many found in the western Pacific Ocean. Most of ...

in the

Tyrrhenian Sea The Tyrrhenian Sea (; it, Mar Tirreno , french: Mer Tyrrhénienne , sc, Mare Tirrenu, co, Mari Tirrenu, scn, Mari Tirrenu, nap, Mare Tirreno) is part of the Mediterranean Sea off the western coast of Italy. It is named for the Tyrrhenian pe ...

opening faster than 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 ...

is colliding with 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 ...

The Norcia earthquake

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

Damage

There was extensive damage in the area around Norcia, with

Spoleto Spoleto (, also , , ; la, Spoletum) is an ancient city in the Italian province of Perugia in east-central Umbria on a foothill of the Apennines. It is S. of Trevi, N. of Terni, SE of Perugia; SE of Florence; and N of Rome. History Spolet ...

and

Rieti Rieti (; lat, Reate, Sabino: ) is a town and ''comune'' in Lazio, central Italy, with a population of 47,700. It is the administrative seat of the province of Rieti and see of the diocese of Rieti, as well as the modern capital of the Sabina re ...

also affected. Modern estimates give a maximum

Mercalli intensity 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 ...

of XI (''Extreme'').

Ground rupture In seismology, surface rupture (or ground rupture, or ground displacement) is the visible offset of the ground surface when an earthquake rupture along a fault affects the Earth's surface. Surface rupture is opposed by buried rupture, where the ...

was observed at several locations and these have been confirmed by modern investigations.

Casualties

Estimates of the death toll vary from 6,240 to 9,761.

The Montereale earthquake

The earthquake occurred at 13:30 UTC on 16 January with an estimated magnitude of 6.2. It is thought to have been caused by movement on the Montereale Fault. Damage was recorded in Montereale,

Cittareale Cittareale is a ''comune'' (municipality) in the Province of Rieti in the Italian region Latium. It is located about northeast of Rome and northeast of Rieti. Cittareale borders the following municipalities: Accumoli, Amatrice, Borbona, Casci ...

Accumoli Accumoli is a ''comune'' (municipality) in the Province of Rieti in the Italian region Lazio, located about northeast of Rome and about northeast of Rieti. It is located in the natural park known as the " Gran Sasso e Monti della Laga National P ...

and Amatrice. Although of lower magnitude than the other two events, this earthquake was still felt in Rome. The estimated intensity for this event is VIII (''Severe''). 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. It was caused by movement on the Mt. Marine Fault.

Damage

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

liquefaction In materials science, liquefaction is a process that generates a liquid from a solid or a gas or that generates a non-liquid phase which behaves in accordance with fluid dynamics. It occurs both naturally and artificially. As an example of the ...

along the

Aterno The Aterno-Pescara (ancient ''Aternus'' from the Greek ''Aternos'', ''Άτερνος'') is a river system in Abruzzo, eastern central Italy. The river is known as the Aterno near its source in the mountains, but takes the name Pescara, actually a ...

River.

Casualties

Estimates of the death toll vary from 2,500 to 5,000.

Summary of earthquakes

Details taken from Catalogue of Strong Earthquakes in Italy (461 BC – 1997) and Mediterranean Area (760 B.C. – 1500)

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. Such sequential adjacent events are examples of

coulomb stress transfer Coulomb stress transfer is a seismic-related geological process of stress changes to surrounding material caused by local discrete deformation events. Using mapped displacements of the Earth's surface during earthquakes, the computed Coulomb stress ...

References

{{DEFAULTSORT:1703 Apennine Earthquakes Earthquakes in Italy Apennine Earthquakes, 1703 Apennine earthquakes Earthquake 1703 History of Abruzzo Earthquake clusters, swarms, and sequences Disasters in Abruzzo

Tectonic setting

The Norcia earthquake

Damage

Casualties

The Montereale earthquake

The L'Aquila earthquake

Damage

Casualties

Summary of earthquakes

Relationship between the events

See also

References