1703 Apennine earthquakes
Encyclopedia
The 1703 Apennine earthquakes were a sequence of three earthquake
s of magnitude
≥6 that occurred in the central Apennines of Italy, over a period of 19 days. The epicenter
s 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. 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.
since the Pliocene
epoch
(i.e. about the last 5 million years), with most of the active fault
s being normal in type and NW-SE trending. 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
.
and Rieti
also affected. Modern estimates give a maximum intensity
of XI (Very Disastrous). Ground rupture was observed at several locations and these have been confirmed by modern investigations.
, Accumoli
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 (Destructive). No separate casualty figures are available for this event.
and liquefaction
along the Aterno
River.
! Name!! Date!! Time!! Coordinates!! Magnitude!! Intensity
|-
| Norcia
| 14 January
| 18:00
| 42.70°N 13.07°W
| 6.7
| XI
|-
| Montereale
| 16 January
| 13:30
| 42.62°N 13.10°W
| 6.2
| VIII
|-
| L'Aquila
| 2 February
| 11:05
| 42.43°N 13.30°W
| 6.7
| X
|-
|}
Earthquake
An earthquake is the result of a sudden release of energy in the Earth's crust that creates seismic waves. The seismicity, seismism or seismic activity of an area refers to the frequency, type and size of earthquakes experienced over a period of time...
s of magnitude
Richter magnitude scale
The expression Richter magnitude scale refers to a number of ways to assign a single number to quantify the energy contained in an earthquake....
≥6 that occurred in the central Apennines of Italy, over a period of 19 days. The epicenter
Epicenter
The epicenter or epicentre is the point on the Earth's surface that is directly above the hypocenter or focus, the point where an earthquake or underground explosion originates...
s were near Norcia
Norcia
Norcia is a town and comune in the province of Perugia in southeastern Umbria, located in a wide plain abutting the Monti Sibillini, a subrange of the Apennines with some of its highest peaks, near the Sordo River, a small stream that eventually flows into the Nera...
(14 January), Montereale
Montereale (AQ)
Montereale is a comune and town in the province of L'Aquila, in the Abruzzo region of Italy. It is located in the natural park known as the "Gran Sasso e Monti della Laga National Park".-See also:*1703 Apennine earthquakes...
(16 January) and L'Aquila
L'Aquila
L'Aquila is a city and comune in central Italy, both the capital city of the Abruzzo region and of the Province of L'Aquila. , it has a population of 73,150 inhabitants, but has a daily presence in the territory of 100,000 people for study, tertiary activities, jobs and tourism...
(2 February), showing a southwards progression over about 36 km. 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 tectonicsExtensional tectonics
Extensional tectonics is concerned with the structures formed, and the tectonic processes associated with, the stretching of the crust or lithosphere.-Deformation styles:...
since the Pliocene
Pliocene
The Pliocene Epoch is the period in the geologic timescale that extends from 5.332 million to 2.588 million years before present. It is the second and youngest epoch of the Neogene Period in the Cenozoic Era. The Pliocene follows the Miocene Epoch and is followed by the Pleistocene Epoch...
epoch
Epoch (geology)
An epoch is a subdivision of the geologic timescale based on rock layering. In order, the higher subdivisions are periods, eras and eons. We are currently living in the Holocene epoch...
(i.e. about the last 5 million years), with most of the active fault
Active fault
An active fault is a fault that is likely to have another earthquake sometime in the future. Faults are commonly considered to be active if there has been movement observed or evidence of seismic activity during the last 10,000 years....
s being normal in type and NW-SE trending. The extension is due to the back-arc basin
Back-arc basin
Back-arc basins are geologic features, submarine basins associated with island arcs and subduction zones.They are found at some convergent plate boundaries, presently concentrated in the Western Pacific ocean. Most of them result from tensional forces caused by oceanic trench rollback and the...
in the Tyrrhenian Sea
Tyrrhenian Sea
The Tyrrhenian Sea is part of the Mediterranean Sea off the western coast of Italy.-Geography:The sea is bounded by Corsica and Sardinia , Tuscany, Lazio, Campania, Basilicata and Calabria and Sicily ....
opening faster than the African Plate
African Plate
The African Plate is a tectonic plate which includes the continent of Africa, as well as oceanic crust which lies between the continent and various surrounding ocean ridges.-Boundaries:...
is colliding
Continental collision
Continental collision is a phenomenon of the plate tectonics of Earth that occurs at convergent boundaries. Continental collision is a variation on the fundamental process of subduction, whereby the subduction zone is destroyed, mountains produced, and two continents sutured together...
with the Eurasian Plate
Eurasian Plate
The Eurasian Plate is a tectonic plate which includes most of the continent of Eurasia , with the notable exceptions of the Indian subcontinent, the Arabian subcontinent, and the area east of the Chersky Range in East Siberia...
.
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 SpoletoSpoleto
Spoleto 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:...
and Rieti
Rieti
Rieti is a city and comune in Lazio, central Italy, with a population of c. 47,700. It is the capital of province of Rieti.The town centre rests on a small hilltop, commanding a wide plain at the southern edge of an ancient lake. The area is now the fertile basin of the Velino River...
also affected. Modern estimates give a maximum intensity
Mercalli intensity scale
The Mercalli intensity scale is a seismic scale used for measuring the intensity of an earthquake. It measures the effects of an earthquake, and is distinct from the moment magnitude M_w usually reported for an earthquake , which is a measure of the energy released...
of XI (Very Disastrous). Ground rupture was observed at several locations and these have been confirmed by modern investigations.
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, CittarealeCittareale
Cittareale is a comune in the Province of Rieti in the Italian region Latium. It is located about 100 km northeast of Rome and 35 km northeast of Rieti....
, Accumoli
Accumoli
Accumoli is a comune in the Province of Rieti in the Italian region Latium, located about 110 km northeast of Rome and about 45 km northeast of Rieti...
and Amatrice
Amatrice
Amatrice is a town and comune in the province of Rieti, in northern Lazio . The city is seat of the food-agricultural base of "Gran Sasso e Monti della Laga National Park".-History:...
. Although of lower magnitude than the other two events, this earthquake was still felt in Rome. The estimated intensity for this event is VIII (Destructive). 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 (Disastrous). The earthquake caused a huge landslide on the Mt. Marine ridge, a large slope failure near PostaPosta (RI)
Posta is a comune in the Province of Rieti in the Italian region Latium, located about 80 km northeast of Rome and about 25 km northeast of Rieti...
and liquefaction
Soil liquefaction
Soil liquefaction describes a phenomenon whereby a saturated soil substantially loses strength and stiffness in response to an applied stress, usually earthquake shaking or other sudden change in stress condition, causing it to behave like a liquid....
along the Aterno
Aterno
The Aterno-Pescara is a river system in Abruzzo, eastern Italy. The river is known as the Aterno near its source in the mountains, but takes the name Pescara, actually a tributary, nearer the city of Pescara and the Adriatic sea.Having the greatest discharge basin of the rivers flowing into the...
River.
Summary of earthquakes
{| class=wikitable! Name!! Date!! Time!! Coordinates!! Magnitude!! Intensity
|-
| Norcia
| 14 January
| 18:00
| 42.70°N 13.07°W
| 6.7
| XI
|-
| Montereale
| 16 January
| 13:30
| 42.62°N 13.10°W
| 6.2
| VIII
|-
| L'Aquila
| 2 February
| 11:05
| 42.43°N 13.30°W
| 6.7
| X
|-
|}