The 1884 Granadan earthquake () occurred on 25 December 1884 at 9:08 p.m in the south of Spain, and had an estimated magnitude of 6.7 . It shook a poor region where many of the houses were built without foundations, with lime or mud mortar, and with weak joints. 10,715 buildings were badly damaged, of which 4,399 were completely destroyed. Fortunately, many people were in the streets celebrating Christmas, or casualties would have been higher, but there were over 1,200 deaths and 1,500 serious injuries. The heavy snow that followed the earthquake caused further suffering and deaths. Help was slow to arrive at first, but as the news spread food and blankets arrived, then tents, and then donations from around the world helped with reconstruction.
Background
The Bética region in the south and southeast of Spain experiences seismic activity caused by the collision of the African Plate and the Eurasian Plate. Within this region, Granada is a zone of moderate seismic activity by world standards, but is a dangerous seismic zone under the Spanish building code. Most earthquakes are of magnitude less than 5.5, but large earthquakes with magnitude greater than 6.5 do occur occasionally. Many of the earthquakes are shallow, at depths of less than , but there are a significant number with hypocenters at depths from . Some rare events have been detected at depths of around .
The slippage rate in the Ventas de Zafarraya fault is about per century. At least two other earthquakes of magnitude 6.5 have occurred along this fault in the last 10,000 years. There are records of earthquakes with epicenters in the region in 1431, 1504, 1518, 1522, 1531, 1645, 1674, 1680, 1748, 1804 and 1829. Historical records show that destructive earthquakes in the Málaga/Granada region occur every 200 years or so.
Destructive earthquakes in the Depression of Granada occurred on 24 April and 27 June 1431 and on 27 October 1806 with epicenters in Santa Elvira near Granada. There were destructive shocks in the Province of Almería in 1804, 1860 and 1863, and in the Region of Murcia in 1828–29 and 1864. A few very weak tremors were felt a day or two before the 25 December 1884 earthquake. Minor shocks were noted at Colmenar and Zafarraya during the night of 24–25 December, and later on 25 December small movements were felt in Málaga and Periana.
Earthquake
The clock at the Real Instituto y Observatorio de la Armada stopped at 9:08 p.m. GMT, or 9:18 p.m. Paris time on 25 December 1884. Magnetographs at Lisbon, Parc de Saint-Maur near Paris, Greenwich and Wilhelmshaven recorded disturbances at 9:09, 9:14, 9:15 and 9:29 respectively. Two observatories near Rome detected slight tremors at or just after 10:00 p.m.
The earthquake caused damage in a zone in the provinces of Granada and Malaga. It was felt as far away as Madrid and Valencia. Later, the French commission estimated that were disturbed by the earthquake, and the Italian commission put the area at . Even the larger estimate must be too small, since the shock was sufficient to ring bells and stop clocks in Madrid. The fracture zone was long, which indicates a moment magnitude of about 6.5 to 6.9. The epicenter was between and . This is between Arenas del Rey and Ventas de Zafarraya. It is on the northern side of the Sierra de Tejeda, nearest to Ventas de Zafarraya.
The shaking was generally thought to have lasted for 15 to 20 seconds, with a noise "like cannon shots" in Arenas del Rey and Jayena, or like loud thunder in Ventas de Zafarraya, Alhama de Granada, Alcaucín, Canillas de Aceituno and Colmenar. In Ventas de Zafarraya and Alhama almost vertical longitudinal waves were followed one or two seconds later by transverse waves. This indicates a depth of focus that was probably less than .
Aftershocks were felt during the night that followed, with one at 2:30 causing the collapse of some of the buildings damaged by the main earthquake. That night aftershocks were also felt in Jayena, Alcaucin, Ventas de Huelma, Motril, Cacín, Dúrcal, and further away in Vélez-Málaga. There were almost daily aftershocks until May, causing further damage in the epicentral area. Significant shocks were felt on 30 December 1884 and in 1885 on 3/5/21 January, 19/27 February, 25 March, 11 April and 13 October.