page_title: 1884 Andalusian earthquake
section_title: Investigations and theories
hierarchical_section_title: 1884 Andalusian earthquake / Investigations and theories
caption_attribution_description: English: Seismic intensity map for the 1884 Andalusian earthquake
context_page_description: The 1884 Andalusian earthquake occurred in Andalusia, in the south of Spain, and had an estimated magnitude of 6.7 Mw.
  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.
context_section_description: On 7 January 1884 the Spanish government appointed a commission to study the earthquake led by the mining engineer Manuel Fernández de Castro y Suero (1825–1895).
  They visited the region at once, circulated a 33-question survey, and on 12 March 1885 issued a report based in part on the survey results.
  They located the focus as 4 kilometres (2.5 mi) deep under the villages of Periana and Guarro.
  The preliminary report devoted seven pages to current theories of earthquake causes, volcanic and non-volcanic, including the internal heat of the earth, high pressure vapors and dissolution of rocks by underground waters. A further seven pages described the orography and hydrography of the provinces of Granada and  Malaga, followed by twenty-one pages on geology that described rock formations and the location and direction of the main fault line.
  The Spanish Commission estimated that 17,178 buildings were damaged, of which 4,899 were totally destroyed. 
  745 people had died and 1,485 had been wounded.
  They concluded that the earthquake was caused by the pressure of water vapor in deep underground strata, from water that had penetrated the permeable rocks above.
  The commission noted that atmospheric pressure had dropped markedly before the earthquake.
  The French Academy of Sciences sent another commission headed by Ferdinand André Fouqué (1828–1904), an Academy member, which prepared a long report with a map.
  The French commission said the atmospheric conditions were irrelevant and the earthquake was related to the region's geology.
  The Italian Government and the Accademia dei Lincei sent the seismologists Torquato Taramelli (1845–1922) and  Giuseppe Mercalli (1850–1912), who also provided a long report on the area's geology with a map of the intensity of the shaking.
  Mercalli thought the earthquake was produced by the build-up of pressure in magma in a region where the crust was too strong to allow a volcanic eruption.
  The Italian team, with access to more information than the Spanish and French commissions, estimated there were 750 deaths and 1,554 severely wounded.
  After careful enquiries, El Defensor de Granada estimated that 828 died and 1,164 were wounded in Granada alone.
  The pioneering geologist José Macpherson y Hemas (1839–1902) explained the earthquake as having been caused by movement along the faults that bound the Tejeda / Almijara massif to the north and south.
  He thought the movement was due to contraction of the earth.
  Others thought the cause might have been the collapse of underground cavities.
  In historical times the only earthquake in Spain that was larger than the 1884 earthquake was that of 1954, which also had an epicenter in Granada, although the destruction in 1954 was not as great.
caption: Seismic intensity map by Taramelli and Mercalli (1886)
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