The 1805 Molise earthquake occurred on 26 July at 21:01

UTC Coordinated Universal Time (UTC) is the primary time standard globally used to regulate clocks and time. It establishes a reference for the current time, forming the basis for civil time and time zones. UTC facilitates international communica ...

. It has an estimated magnitude of 6.6 on the equivalent magnitude scale (M_e) (calculated from seismic intensity data) and a maximum perceived intensity of X on the

Mercalli intensity scale The Modified Mercalli intensity scale (MM, MMI, or MCS) measures the effects of an earthquake at a given location. This is in contrast with the seismic magnitude usually reported for an earthquake. Magnitude scales measure the inherent force or ...

. The area of greatest damage was between the towns of

Isernia Isernia () is a town and ''comune'' in the southern Italian region of Molise, and the capital of the province of Isernia. Geography Situated on a rocky crest rising from between the Carpino and the Sordo rivers, the plan of Isernia still refl ...

and

Campobasso Campobasso (, ; ) is a city and ''comune'' in southern Italy, the capital of the region of Molise and of the province of Campobasso. It is located in the high basin of the Biferno river, surrounded by Sannio and Matese mountains. Campobas ...

, while the area of intense damage extended over about 2,000 square kilometres. There were an estimated 5,573 deaths resulting from this earthquake and two of the

aftershock In seismology, an aftershock is a smaller earthquake that follows a larger earthquake, in Epicenter, the same area of the Mainshock, main shock, caused as the displaced Crust (geology), crust adjusts to the effects of the main shock. Large earthq ...

Tectonic setting

The Southern

Apennines The Apennines or Apennine Mountains ( ; or Ἀπέννινον ὄρος; or – a singular with plural meaning; )Latin ''Apenninus'' (Greek or ) has the form of an adjective, which would be segmented ''Apenn-inus'', often used with nouns s ...

originated as northeast moving

fold and thrust belt A fold and thrust belt is a series of mountainous foothills adjacent to an orogenic belt, which forms due to contractional tectonics. Fold and thrust belts commonly form in the forelands adjacent to major orogens as deformation propagates outwards ...

. Since the Middle

Pleistocene The Pleistocene ( ; referred to colloquially as the ''ice age, Ice Age'') is the geological epoch (geology), epoch that lasted from to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was fin ...

, the tectonics has been dominated by

extension Extension, extend or extended may refer to: Mathematics Logic or set theory * Axiom of extensionality * Extensible cardinal * Extension (model theory) * Extension (proof theory) * Extension (predicate logic), the set of tuples of values that ...

. The axial part of the Apennines is the most seismically active, with a series of damaging historical earthquakes up to about 7 in magnitude. The major

normal fault In geology, a fault is a planar fracture or discontinuity in a volume of rock across which there has been significant displacement as a result of rock-mass movements. Large faults within Earth's crust result from the action of plate tectonic ...

in the epicentral area of the 1805 event is the Bojano fault system.

Earthquake

The earthquake was a result of movement on the NW–SE trending Bojano fault system. A

surface 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 (geology), fault affects the Earth's surface. Surface rupture is opposed by buried rup ...

of 40 km has been attributed to this event, with a maximum displacement of 150 cm. The mainshock was preceded by a series of low intensity

foreshock A foreshock is an earthquake that occurs before a larger seismic eventthe mainshockand is related to it in both time and space. The designation of an earthquake as ''foreshock'', ''mainshock'' or aftershock is only possible after the full sequenc ...

s throughout the previous day. The aftershock sequence continued until the following June.

Damage

The damage was particularly intense in the foothills of the

Matese The Matese (Italian: Monti del Matese or Massiccio del Matese) is a chain of mountains in southern Apennines, southern Italy. Geography The Matese mountains straddle two regions (Molise and Campania) and four provinces (Campobasso, Isernia, Ben ...

massif and the Bojano plain, with 30 towns and villages being severely affected. Damage was recorded as far away as

Naples Naples ( ; ; ) is the Regions of Italy, regional capital of Campania and the third-largest city of Italy, after Rome and Milan, with a population of 908,082 within the city's administrative limits as of 2025, while its Metropolitan City of N ...

and

Salerno Salerno (, ; ; ) is an ancient city and ''comune'' (municipality) in Campania, southwestern Italy, and is the capital of the namesake province, being the second largest city in the region by number of inhabitants, after Naples. It is located ...

. Landslides and other slope failures were seen over an area of about 5,300 square kilometres. The official number of recorded deaths is given as 5,573, representing nearly 3% of the area's inhabitants, with a further 1,583 injured. Other estimates of the death toll are in the range 4,000 to 6,000.

Aftermath

Response

The most affected area lay within the then

Kingdom of Naples The Kingdom of Naples (; ; ), officially the Kingdom of Sicily, was a state that ruled the part of the Italian Peninsula south of the Papal States between 1282 and 1816. It was established by the War of the Sicilian Vespers (1282–1302). Until ...

. The king, Ferdinand IV, took control of the response to this disaster. He sent Gabriele Giannocoli, a tax lawyer, to visit those areas of the countryside that has suffered the most, to evaluate the situation and to do what needed to be done. He was given considerable powers, together with the financial means, to allow him to carry out his task. He concentrated on visiting the most damaged areas, relying on reports from other officials in less affected parts. At his request, soldiers were sent to restore order and to prevent looting in some areas. Only properties in a dangerous state were repaired or demolished. Temporary shelters were provided for the homeless and huts for use as hospitals. Taxes were suspended by the king for all of the countryside around Molise in August.

References