1930 Irpinia earthquake
Encyclopedia
The 1930 Irpinia earthquake occurred at 00:08 UTC on 23 July 1930. It had a magnitude
of 6.6 and caused 1,404 deaths. The epicenter
was close to the borders between the regions of Basilicata
, Puglia and Campania
.
has been characterised by extensional tectonics
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
. To the northeast of the Apennine chain, the foreland is in contrast affected by W-E trending strike-slip to oblique-slip faults.
, the Crathis
valley, and the Biferno
and Murgia
areas, including parts of high Irpinia
, the Vulture
, Sannio
, Salerno
, Naples
, the province of Matera
and high Puglia. In the most damaged areas, about 70% of the houses were completely destroyed, made worse by the poor quality of the buildings. The death toll was 1,404, with 75% of the victims being in the province of Avellino
. The death toll was low considering the level of damage, a fact explained by the number of villagers who were sleeping in the fields during the wheat harvest.
The greatest intensity of X (very destructive) on the European Macroseismic Scale
was recorded at Aquilonia Vecchia
, Lacedonia
and Villanova del Battista
. Intensities of IX (destructive) were recorded at Anzano degli Irpini
, Scampitella
, Castel Baronia
, Melfi
, Montecalvo Sant'Antonio and Trevico
.
The area of maximum intensity is elongated in a roughly W-E direction. Analysis of historical seismograph recordings suggest that the earthquake originated from a north-dipping fault plane striking N100°E.
Surface wave magnitude
The surface wave magnitude scale is one of the magnitude scales used in seismology to describe the size of an earthquake. It is based on measurements in Rayleigh surface waves that travel primarily along the uppermost layers of the earth...
of 6.6 and caused 1,404 deaths. 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...
was close to the borders between the regions of Basilicata
Basilicata
Basilicata , also known as Lucania, is a region in the south of Italy, bordering on Campania to the west, Apulia to the north and east, and Calabria to the south, having one short southwestern coastline on the Tyrrhenian Sea between Campania in the northwest and Calabria in the southwest, and a...
, Puglia and Campania
Campania
Campania is a region in southern Italy. The region has a population of around 5.8 million people, making it the second-most-populous region of Italy; its total area of 13,590 km² makes it the most densely populated region in the country...
.
Tectonic setting
The central and southern part of the ApenninesApennine mountains
The Apennines or Apennine Mountains or Greek oros but just as often used alone as a noun. The ancient Greeks and Romans typically but not always used "mountain" in the singular to mean one or a range; thus, "the Apennine mountain" refers to the entire chain and is translated "the Apennine...
has been characterised by extensional tectonics
Extensional 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...
. To the northeast of the Apennine chain, the foreland is in contrast affected by W-E trending strike-slip to oblique-slip faults.
Damage
The area affected was about 6,300 km2, between the Garigliano RiverGarigliano River
The Garigliano is a river in central Italy.It forms at the confluence of the rivers Gari and Liri. Garigliano is actually a deformation of "Gari-Lirano"...
, the Crathis
Crathis
The Crathis or Crater is a river in Calabria, southern Italy. It rises in the central the Sila Mountains, a few kilometers south of Cosenza, flows below the walls of that city, where it is joined by the smaller stream of the Busento, and has a course nearly due north through the center of the...
valley, and the Biferno
Biferno
The Biferno is a river of Molise, in southern Italy. Its source is in the comune of Bojano and during the first few kilometres of its course it receives the waters of numerous streams which flow from the Matese mountains...
and Murgia
Murgia
Murgia is a sub-region of Apulia in southern Italy, corresponding to a karst topographic plateau of rectangular shape, occupying the central area of the region. The name stems from the Latin murex, meaning "sharp stone"....
areas, including parts of high Irpinia
Irpinia
Irpinia is a region of the Apennine Mountains around Avellino, a town in Campania, South Italy about 40 km east of Naples...
, the Vulture
Vulture area
The Vulture is a geographical and historical subregion of Italy that lies in the Province of Potenza, Basilicata region.-Overview:...
, Sannio
Sannio Hills
The Sannio Hills are a chain of hills located in the province of Benevento, Campania, southern Italy.The Sannio hills have long been considered a particularly fertile zone of Italy. The ancient Greeks knew this region as a land for growing olives. Today a variety of crops are grown besides olives...
, Salerno
Salerno
Salerno is a city and comune in Campania and is the capital of the province of the same name. It is located on the Gulf of Salerno on the Tyrrhenian Sea....
, Naples
Naples
Naples is a city in Southern Italy, situated on the country's west coast by the Gulf of Naples. Lying between two notable volcanic regions, Mount Vesuvius and the Phlegraean Fields, it is the capital of the region of Campania and of the province of Naples...
, the province of Matera
Province of Matera
The Province of Matera is a province in the Basilicata region of Italy. Its capital is the city of Matera.It has an area of 3,447 km², and a total population of 203,837 . There are 31 comunes in the province . The main comunes by population are:- External links :* **...
and high Puglia. In the most damaged areas, about 70% of the houses were completely destroyed, made worse by the poor quality of the buildings. The death toll was 1,404, with 75% of the victims being in the province of Avellino
Province of Avellino
The Province of Avellino is a province in the Campania region of Italy. The area is typified by many small towns and villages scattered across the province; in fact only two towns have a population over 20,000; its capital city Avellino and Ariano Irpino....
. The death toll was low considering the level of damage, a fact explained by the number of villagers who were sleeping in the fields during the wheat harvest.
Characteristics
The main shock was preceded by two foreshocks a few hours earlier and followed by 16 aftershocks within the first 24 hours.The greatest intensity of X (very destructive) on the European Macroseismic Scale
European Macroseismic Scale
The European Macroseismic Scale is the basis for evaluation of seismic intensity in European countries and is also used in a number of countries outside Europe...
was recorded at Aquilonia Vecchia
Aquilonia
Aquilonia is a town and comune in the province of Avellino, part of the Campania region of southern Italy. It is situated in mountainous terrain in the eastern part of Avellino, at an elevation of 750 m...
, Lacedonia
Lacedonia
Lacedonia is a comune of 3,010 people in the province of Avellino, Italy, overlooking the Osento River, which flows into the Lago di San Pietro , an artificial lake.-History:...
and Villanova del Battista
Villanova del Battista
Villanova del Battista is a town and comune in the province of Avellino, Campania, Italy....
. Intensities of IX (destructive) were recorded at Anzano degli Irpini
Anzano di Puglia
Anzano di Puglia is a town and comune in the province of Foggia in the Apulia region of southeast Italy.According to the results of the national census made in 1991 Anzano di Puglia has a population of 2,239 inhabitants , a surface of 11.12 square kilometers and a population density of 201.3...
, Scampitella
Scampitella
Scampitella is a town and comune in the province of Avellino, Campania, Italy....
, Castel Baronia
Castel Baronia
Castel Baronia is a town and comune in the province of Avellino, Campania, Italy.Castel Baronia has a population of 1,233 inhabitants and a surface of 15.3 square kilometers thus showing a population density of 80.59 inhabitants per square kilometer. It rises 639 metres above the sea level...
, Melfi
Melfi
Melfi is a town and comune in the Vulture area of the province of Potenza, in the Southern Italian region of Basilicata.-Geography:On a hill at the foot of Mount Vulture, Melfi is the most important town in Basilicata's Vulture, both as a tourist resort and economic centre.-Early history:Inhabited...
, Montecalvo Sant'Antonio and Trevico
Trevico
Trevico is a town and comune in the province of Avellino, Campania, Italy....
.
The area of maximum intensity is elongated in a roughly W-E direction. Analysis of historical seismograph recordings suggest that the earthquake originated from a north-dipping fault plane striking N100°E.