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DEVELOPMENT OF SEISMOLOGY IN SPAIN IN THE CONTEXT OF THE THREE LARGE EARTHQUAKES OF 1755, 1884 AND 1954

AGUSTÍN UDÍAS

Departamento de Geofísica y Meteorología

Facultad C. Físicas, Universidad Complutense de Madrid 28040 Madrid, Spain audiasva@fis.ucm.es

Earth Sciences History Vol. 32, No. 2, 2013

pp. 000–000

ABSTRACT The occurrence of large earthquakes is in many cases a catalyst for the advancement of seismology. This article examines the influence of the three large earthquakes of 1755, 1884 and 1954, felt in the Iberian peninsula, in the development of seismology in Spain. The 1755 earthquake was the occasion for the establishment of the study of earthquakes as natural phenomena outside of religious considerations and the introduction of modern ideas about the origin of earthquakes. The 1884 earthquake was the first earthquake in Spain subject to a serious and detailed scientific study by three commissions from Spain, France and Italy. This led to the introduction in Spain of modern ideas about the study of earthquakes and their tectonic origin. It showed also the need for installing seismographic stations. The 1954 deep earthquake was the occasion for a renewed interest in Spain for seismology, improvements in the seismographic stations and the beginning of international cooperation.

1. INTRODUCTION

It is an interesting fact that the study of the history of seismology is marked by the occurrence of large earthquakes. Their impact has provided new observations and has stimulated proposals of new ideas regarding their nature and consequences (Bolt 1993, pp. 1–23). In 1760 John Michell (1724–1788) proposed for the first time the fundamental idea that earthquake motion propagates through the Earth’s crust in the form of waves through. Michell’s proposal was motivated by the occurrence of the Lisbon earthquake of 1 November 1755. Seismology was subsequently established as a modern science at the end of the nineteenth century and the beginning of the twentieth century, with the development of the first instruments (seismographs) to detect, measure and record the ground motion produced by earthquakes and with the application of elasticity theory to the propagation of seismic waves (Davison 1927). Throughout seismology’s history important contributions have been made after the occurrence of large earthquakes. Robert Mallet’s (1810–1881) study of the 16 December 1857 Naples earthquake is considered as marking the beginning of modern seismology. For the first time, he joined the naturalistic description of phenomena with a rigorous physical–mathematical analysis, integrating geology, physics and mathematics in the study of an earthquake. Other examples are the presentation of the elastic rebound theory for the mechanism of earthquakes by Harry F. Reid (1859–1944) after the San Francisco earthquake of 1906 and the development of the theory of free oscillations of the Earth after the large earthquakes of Kamchatka in 1954 and Chile in 1960. In this article I try to follow the development of seismology in Spain in the context of the occurrence of three large earthquakes in 1755, 1884 and 1954 that affected the Iberian Peninsula. The occurrence of these earthquakes occasioned developments that influenced the history of seismology in Spain. As a consequence we can organize its early developments around these three shocks. The main interest in this article is the presentation of the specific developments of seismology in Spain. More general problems of the history of Earth sciences will not be examined.

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2. THE LISBON EARTHQUAKE AS IT AFFECTED SPAIN On 1 November 1755 at about 9.40 a.m. local time, an extraordinarily large earthquake, the largest felt in Europe in historical times, caused heavy damage to the city of Lisbon (for recent overviews see Fonseca 2004, Machete (ed.) 2005, and Mendez-Victor et al. (eds.) 2009). Its magnitude has been estimated as between 8 and 9 in the magnitude-moment scale. Half an hour after its occurrence, waves from the tsunami that it generated added to the destruction (see Figure 1). Estimates of casualties in Lisbon buried under the ruins or affected by the tsunami and by the subsequent fires vary between 10,000 and 20,000. The source of the earthquake has been located somewhere offshore from Cape San Vicente. The tectonic structures responsible for such a large earthquake are not yet fully understood and several proposals have been made (Baptista and Miranda 2009). The earthquake was felt over the entire Iberian Peninsula, producing damage in the nearby region of southwest Spain, especially in the cities of Huelva, Cadiz and Seville. It caused 1,276 deaths in Spain, mostly due to the tsunami in the coastal towns of the provinces of Cadiz and Huelva. About 200 people were drowned in the city of Cadiz and about 400 in Ayamonte (Huelva) (Martínez Solares 2001, Martínez Solares and Lopez Arroyo 2004). This extraordinary event produced an abundant literature published in Spain, especially in Seville (Udías and López Arroyo 2009).  Many of the publications were brief popular accounts (most of them anonymous and some were written in verse) about how the earthquake was felt in some particular localities, or presented religious considerations about the event. These anonymous publications were generally works of only a few pages of a popular character with exaggerated accounts of damage, or extraordinary and curious occurrences during the earthquake. Some assigned the earthquake to a punishment by God and asked for the pardon of sins or gave thanks for the deliverance from the effects of the earthquake. Other publications were extended treatises on the physical, philosophical and religious aspects of the event, written by scientists, philosophers and theologians. In these treatises two main topics were addressed which marked a preliminary approach to the study of earthquakes in Spain. The first was the consideration of the natural or supernatural character of the earthquake and the second the search for its natural causes in terms of the traditional Aristotelian doctrine or of modern ideas of explosive or electrical sources.

Figure 1. German eighteenth-century engraving with an imagined representation of the damage produced in Lisbon by the 1755 Earthquake (marialynce.wordpress)

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3. NATURAL OR SUPERNATURAL EVENT? Although Medieval natural philosophers and theologians, such as Albertus Magnus and Thomas Aquinas in the thirteenth century, had already interpreted the natural causes of earthquakes according to Aristotelian doctrine, it was common in popular and religious accounts up to the eighteenth century to consider them as God’s punishment for the sins of the people (Chester and Duncan 2009, Udías 2009). Immediately after its occurrence the Lisbon earthquake brought this question in Spain to an explicit and intense focus. Many of the anonymous publications that appeared in Seville after the earthquake took it for granted that the earthquake has been God’s punishment for the sins of the people (e.g. Anonymous 1755, Anonymous 1756). Two sermons by Francisco Olazaval y Olayzola, Canon of the Cathedral of Seville, both of which were later published, strongly argued this interpretation (Olazaval y Olayzola 1755). He insisted that the many sins of the city of Seville were the cause of this punishment, which God’s mercy had prevented from being even greater. The strongest defender of the supernatural character of the earthquake was Miguel de San José (1682–1757), Bishop of Guadix and Baza (Granada), who in a short letter rejected the opinions of those who regarded it as a natural event. He affirmed: “to deny or doubt that earthquakes and other disasters are usually the effect of the wrath of God can be considered as an error in the faith” (San José 1756). He singled out José de Cevallos in his criticism. Similarly, Thomas del Valle (1703–1776), Bishop of Cadiz, expressed the view that God had punished the people of Cadiz for their sins and called for their repentance (Del Valle 1755). This was not only a Spanish Catholic position. In Protestant England the influential John Wesley (1703–1791), founder of the Methodist movement, argued in his sermons that the earthquake was only explicable if it were a divine punishment (Israel 2011, pp. 39–50).

On the other side of the debate, there was serious questioning about attributing the earthquake to a direct action by God. José de Cevallos (1714–1776), a theologian from Seville and later Rector of the University, was the strongest defender of the view that the earthquake was a natural event. He affirmed that: “the earthquake has been entirely natural, caused by natural and proportioned secondary causes in which God takes part as in any other natural effect” (Cevallos 1756). Among those who defended this position was Juan Luis Roche, a physician of Seville, who maintained that there was no relation between sins committed and the occurrence of earthquakes. He added that those are only the “pious opinions of theologians” and rhetorically asked: “Are Lisbon and Seville worse than other cities?” (Roche 1756). Both Cevallos and Roche supported their opinions with the authority of Benito Jerónimo Feijoo y Montenegro (1674–1764), a Benedictine professor of theology in the University of Oviedo and a key figure in the Spanish Enlightenment, influential in the introduction of modern scientific ideas, such as Newtonian physics, into Spain (Lafuente and Selles, 1980). Feijoo defended the natural character of the earthquake, but—already an old man—he did not enter the controversy. Of those defending the natural character of the earthquake there were some who considered that, although a natural event, God could have used it to punish or caution sinners. Among others, Miguel Cabrera, a theologian of Seville of the Order of Minims, and Francisco Buendía y Ponce (1721–1800), priest and physician of Seville, proposed this ‘mixed’ position (Udías 2009).

The Lisbon earthquake was, then, the occasion for the public defence in Spain of the view that earthquakes and other natural disasters are natural events and should be studied from a purely naturalistic point of view and staying away from theological considerations. This position was defended by Spanish authors who upheld the new ideas of the Enlightenment (called in Spain ilustrados). The Spanish debate was part of the general controversy in Europe provoked by the occurrence of the earthquake that has been called the ‘eighteen-century earthquake theology’ (Kendrick 1955; Israel 2011, pp. 39–50). The earthquake cast doubt on the optimism of the times, which held that the world was a good place in which everything that happens was viewed to be for the best. A special target of the attacks, such as those contained in François Marie Arouet’s (Voltaire) (1694–1778) popular novel Candide, was Gottfried Wilhem Leibniz’s (1646–1716) optimistic theodicy, which held that this was ‘the best of all possible worlds’. But in Spain, this question was not treated and the controversy centered instead on the natural or

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supernatural character of the earthquake. The position held by the ilustrados in Spain was that in the studies of the occurrence of earthquakes, only their natural causes must be considered and theological considerations must be excluded. This was an important step in the progress toward a purely natural approach to the study of earthquakes. This position was publicly defended in several lectures presented between 1755 and 1756 at the Academia de Buenas Letras in Seville, a learned society where enlightened ideas were discussed. Although ecclesiastics participated in these conferences, the Academia did not involve itself in formal theological discussions (Sánchez-Blanco 1999).

4. THE NATURE OF EARTHQUAKES: ARISTOTELIAN OR MODERN IDEAS? Interest in the investigation of the causes of earthquakes on purely rational grounds can be traced back to the early Greek natural philosophers of the fifth and fourth century BC, such as Anaxagoras, Empedocles and Democritus. In the fourth century BC, Aristotle proposed in the 2nd book of Meteorologica his explanation in terms of exhalations or winds trapped in cavities of the Earth’s interior, which in escaping caused its shaking (Wildorf and Schmidt, 1981). This theory was accepted in the West with few modifications through the Middle Ages till the end of the seventeenth century (Guidoboni 1998). With the rise of modern science, this theory was substituted by a theory of explosive sources, or chemical reactions, proposed in 1684 by Nicolas Lémery (1645–1715) in France and in 1700 by Martin Lister (1669–1712) in England. Isaac Newton (1642–1727) in his Opticks (Book 2, p. 1, q. 31) and George Louis de Buffon (1707–1788) in Histoire et théorie de la Terre (1704) also supported this kind of theory (Taylor 1975).

But in Spain in the eighteenth century, Aristotelian natural philosophy was still widely accepted and modern science was only slowly introduced (Vernet-Ginés 1975, 135–152). Regarding the nature of earthquakes, in the seventeenth and eighteenth centuries, the Aristotelian ideas were mixed with organicist notions, in which the Earth was compared with a living organism (Due-Rojo 1945). In this respect there was an important influence on Spanish authors of the work Mundus subterraneus (1641) by Athanasius Kircher (1601–1680), a Jesuit professor of the Collegio Romano (Rome) (Glick 1971, Findlen 2004, Fletcher 2011). Kircher proposed the existence of conduits in the interior of the Earth, called by him, pyrophylacia, hydrophylacia and aerophylacia, through which fire, water and air circulated. The first were related to volcanoes and were supposedly connected with a central fire. Kircher thought earthquakes were related to the interaction between these three systems of conduits. Fire brought into contact with the air will cause it to expand and produce the shaking (Capel 1980; Godwin 2009, pp. 127–142). After the Lisbon earthquake, in Spain some authors such as Francisco Mariano Nifo y Cagigal (1719–1803), founder of the first newspaper in Madrid, still adhered to the Aristotelian ideas, though with some minor changes. Cabrera following Kircher, presented a different system consisting of a large cavity in the interior of the Earth, following its axis, with many branches, in which water and winds circulate (Cabrera 1756). He called this cavity the vena cava, by analogy with the main vein in the human body. In fact Cabrera thought that this cavity and its branches in the Earth functioned as do veins in animals and humans. All phenomena in the Earth (winds, fountains, earthquakes, etc.) were supposedly explained in terms of this system, in analogy with the functions of veins in living organisms. Thus, earthquakes were said to be ‘sicknesses of the Earth’. In the Lisbon earthquake, the ramifications of the vena cava explained how its effect was felt as far away as Germany. He rejected the opinions of Nifo, Cevallos and Feijoo and their attacks on Aristotle, and extended his criticisms to the modern ideas of René Descartes (1596–1650) and Newton.

In opposition to the Aristotelian doctrine, some authors used the Lisbon earthquake to present the modern theories of the explosive nature of earthquakes along the lines of Lister and Lémery. Antonio del Barco (1716–1784), who wrote in Huelva, where the earthquake was very strongly felt, compared the origin of the earthquake with an explosion in a mine (Del Barco 1756). For him, following Lister and Lémery, the accumulation of inflammable materials like sulfur, niter, coal and bitumen inside the Earth caused the explosions by the contact with rarified

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air and fire. Barco answered the question of where the Lisbon earthquake had its origin and located its ‘focus’ under the ocean nearer to the African coast than Portugal. This location is close to the modern estimates, which locate its epicenter near the Gorringe Bank (beneath the Atlantic Ocean southwest of Portugal). He also explained the occurrence of aftershocks as produced by the explosion of materials that had not exploded in the first shock. Roche likewise assigned the cause of the earthquake to the explosion of the mixture of inflammable materials within the Earth, and made reference to Lémery and Isidoro Ortiz Gallardo de Villarroel, who was author of the first book on earthquakes published in Spain and combined their explosive nature with Kircher’s theory, assigning their cause to the fire conduits that brought the fire in contact with accumulated inflammable material thereby causing explosions (Ortiz Gallardo de Villarroel 1755).

Feijoo y Montenegro presented the most ‘modern’ ideas about the origin of earthquakes in his five letters on the subject (Feijoo y Montenegro 1756, Glendinning 1966, Ordaz 1983). After refuting in the third letter the ideas commonly held at the time for the cause of earthquakes, especially the collapse of underground cavities and the explosion of inflammable material inside the Earth, he presented in his fourth letter his preferred theory according to which earthquakes are produced by electrical discharges (see Figure 2). He stated that just as lightning and thunder are produced in the atmosphere by the electricity of clouds earthquakes are caused by the electricity accumulated inside the Earth by vitreous materials. This was not an original idea, other authors having proposed it previously, among them William Stuckley (1687–1765) in England in 1750 and Giovanni Battista Beccaria (1716–1781) in Italy in 1753 (Taylor 1975). Feijoo did not mention these authors and probably did not know about their work as he claimed a originality for his theory. For him the electrical theory explained Lisbon earthquake well, as it was felt at almost the same time in distant places and electricity propagates at a very high velocity. However, he did not completely rule out an explosive nature as electricity could also have caused the explosion of the inflammable materials trapped inside the Earth.

Figure 2. Benito Gerónimo Feijoo’s publication of the electrical theory of earthquakes (1756) (Archivo Instituto Geográfico Nacional, Madrid).

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The acceptance of modern theories about the origin of earthquakes by, for example, Barco, Ortiz and Feijoo, was part of the process of the introduction of modern science into Spain and the abandonment of the Aristotelian ideas. But this was a long process beginning in the late seventeenth century, with a half-century delay relative to the scientific developments elsewhere in Europe (López-Piñero 1969). The eighteenth century in Spain was a period of assimilation and reflection about these developments trying to fill the gap created with respect to science in the rest of Europe and to incorporate the new advances of science (Romeu de Armas 1980, pp. 103–123). The Lisbon earthquake was the occasion for a step forward in this process in the particular field of the study of earthquakes.

5. THE ANDALUSIAN EARTHQUAKE OF 1884 On 25 December 1884 at 8.45 p.m. a large earthquake with an estimated magnitude of 6.5 shook the region of Andalusia in southern Spain (Udías and Muñoz 1982). More than 100 villages situated between Granada and Malaga suffered very heavy damage. Arenas del Rey, Ventas de Zafarraya and Alhama de Granada received particularly severe damage and were practically destroyed so that they had to be completely rebuilt (see Figure 3). The number of casualties was 745 dead and 1,485 seriously injured. The total number of damaged buildings was about 17,000. Shaking was felt as far away as Madrid and Valencia. Aftershocks continued to be felt for more than a year.

Figure 3. Damage in Arenas del Rey (Granada) of the 1884 Andalusian Earthquake (Orueta y Duarte, 1885).

These numbers do not in themselves reflect the enormous commotion that this earthquake caused in Spain. Villages affected by the earthquake were, at that time, rather impoverished and with poor communications. A harsher than usual winter, with heavy snowfall on the affected area after the earthquake, added to the misery of those that had lost their homes. But aid to the victims was rapidly organized and a public collection raised three millions pesetas in Spain and a similar sum in other countries. The young King of Spain, Alfonso XII (1857–1885), already in

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poor health (he died at the end of the year) made an exhausting journey, visiting the damaged villages between 10 and 20 January (see Figure 4). He visited twenty-five villages riding on horseback, sometimes through heavy snowstorms. Some have thought that this journey may have hastened his death. In memory and gratitude for his visit a monument was erected in the town of Alhama de Granada with a statue of the King. The earthquake was extensively reported in the newspapers. For example, in its issues of 13, 22 and 30 January the Madrid illustrated weekly, La Ilustración Española y Americana, published details of the damage with nineteen illustrations from drawings and photographs of the damage and the King’s journey. The Seville poet, Carolina de Soto y Corro (1860–1904), wrote a long and heartfelt poem on the subject (de Soto y Corro 1885).

Figure 4. Visit of King Alfonso XII to victims affected by the 1884 earthquake (La Ilustración Española y Americana, 30 January 1885).

6. FIRST SCIENTIFIC STUDIES OF AN EARTHQUAKE IN SPAIN

The earthquake of 1884 was the first in Spain to be the subject of modern scientific study. Three official commissions were established: the first by the Spanish Government on 7 January 1884, headed by Manuel Fernandez de Castro (1825–1895), a mining engineer and Director of the Commission for the Geological Map of Spain (Comisión del Mapa Geológico de España). This Commission had been established in 1849 and reorganized in 1873 (Huerga 2000, Rabano and Aragón 2007). It was the first official institution dedicated to the sciences of the Earth in Spain and was mostly formed by mining engineers. The School of Mining Engineering (Escuela Superior de Ingenieros de Minas) had been established in Madrid in 1777 and from 1857 it awarded the title of Mining Engineer (Ingeniero de Minas) to its graduates. Most Spanish fieldwork in geology was carried out under the aegis of this institution. At that time there was a certain tension in Spain between geologists from the Academy and mining engineers who occupied official posts (Catalá-Gorgues and Carneiro 2012). The teaching of geology in the

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Spanish universities after the reforms of 1853 (Ley Moyano) was undertaken in the faculties of natural sciences (Facultades de Ciencias Naturales) (Peset and Peset 1974). The commission for the study of the earthquake was made up of Fernandez de Castro, three other mining engineers (Juan Pablo Lasala, Daniel de Cortázar and Joaquín Gonzalo y Tarín) and three assistants, all members of the Commission for the Geological Map of Spain. The commission immediately travelled to the affected region and distributed a detailed survey of thirty-three questions throughout the provinces where the earthquake had been felt. Their report was partly based on the answers to this survey. Of 105 pages, it was finished on 12 March 1885 and published on 30 March (Fernández de Castro et al. 1885). It contained a summary of the current seismic theories, the orography, hydrography and geology of the provinces of Granada and Malaga, the characteristics of the earthquake: origin time, extension, focus, depth, duration, damage and other phenomena. It concluded that the earthquake happened at 8h 55m 55s, Madrid time (the time was accurately determined by the stopping of a clock at the Naval Observatory of San Fernando in Cadiz), its focus was located in the Zafarraya Valley in Granada Province and the mountains of Tejeda, Marchamonas and Enmedio, in an area of 200 square kilometres. The investigators assigned the location of the focus to a point under the villages of Periana and Guarro at a depth of four kilometres but were unable to be more precise. The report gave the Rossi–Forel scale of intensities and described the area corresponding to each grade, assigning the maximum (Level 10) to the area containing the villages with greatest destruction (Alhama, Zafarraya, Jayena, etc). However, it did not summarize the intensities on a map. The report also proposed some simple norms for the reconstruction of the buildings so that damage could be minimized in future earthquakes.

The second commission was established by the French Académie de Sciences under the direction of Ferdinand André Fouqué (1828–1904), Professor at the Collége de France and a member of the Academy. Its members were Professor Charles Barrois (1851–1939) of the University of Lille, the mining engineers Michel Levy and Marcel Bertrand, and four assistants. They left Paris on February and visited the effected region during the month of March. They dedicated most of their effort to the study of the geology of the area. Their results were presented in a long report published in 1890 (Fouqué 1890). It included a map, which according to the intensities of shaking, divided the region into three areas: epicentral, mean, and external. The map also showed the direction of shaking at various places. The report included eight photographs of the damage and ground effects. It was translated into Spanish and published by the Commission of the Geological Map with a long commentary of sixty-one notes where its members disagreed from the French commission (Comisión del Mapa Geológico 1890/1893). The notes made clear the rivalry between the two commissions and the Spaniards’ resentment of the superiority manifested by the behaviour of the Frenchmen. Fouqué had published two studies about the earthquake before the publication of the report of the Commission (Fouqué 1886, 1888).

The third commission was established by the Real Accademia dei Lincei and the Italian Government. It consisted of the renowned seismologists Torquato Taramelli (1845–1922) and Giuseppe Mercalli (1850–1912). They left Italy in April. Their long report was presented to the Academy in June 1885 and published the following year (Taramelli and Mercalli 1886). The authors presented a detailed study of the geology of the region and the damage produced by the earthquake, adding a catalogue of earthquakes in Andalusia back to 1,000 AD. It was one of the earliest catalogues of earthquakes in southern Spain. Taramelli and Mercalli presented a map dividing the region according to the strength of the shaking in three areas named: disastroso, rovinoso and fortissimo (see Figure 5). This can be considered an early precursor of the present intensity, or isoseismal, maps. In 1902, Mercalli established his famous seismic intensity scale, which, with some modifications, is still widely used today (the Modified Mercalli Scale). From the seismological point of view this can be considered as the most complete of the three studies. The Italians determined the epicentre more precisely at the northern side of the mountains of Sierra Tejeda near Ventas de Zafarraya and the focus at a depth of 12,300 metres. They

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compared the intensity of this earthquake with that of the great Naples earthquake of 1857 (studied by Mallet), finding the latter to be three times larger.

Figure 5. Seismic intensity map for the 1884 earthquake by Taramelli and Mercalli (1886) (Archivo Instituto Geográfico Nacional, Madrid) .

Domingo Orueta y Duarte (1862–1926), a student of the Mining Engineering School in

Madrid and later Professor of Geology in the Mining School of Mieres (Asturias), also carried out an interesting field study of this earthquake (Orueta y Duarte 1885). He was in Malaga at the time of the earthquake and with the permission of his professors he took the time to carry out a field survey of the damage and was excused from attending lectures. He produced a detailed map of the distribution of the intensity of the motion over the region according to four categories, numbered 1–4 from more to less intense, described the damage and discussed the geology. The report contained the best photographic collection that was made of the damage and ground effects produced by the earthquake, with twenty-two photographs.

Cesáreo Martínez y Aguirre (1853–1923), a teacher at the secondary school of Malaga, published a book on the earthquake, collecting the articles published in the Malaga newspaper El Mediterráneo from 7 to 20 January (Martínez y Aguirre 1885). After describing the damage at different towns and villages, he dedicated considerable space to explaining the nature of earthquakes according to recent theories. He presented the Rossi–Forel scale of intensities and gave a table of the intensities, together with the time and duration of shaking, at thirty-six places in Malaga Province and fifty-four in Granada Province. However, he did not depict them on a map, which, had he done so, would have been the most up to date intensity map for this earthquake. Martínez y Aguirre seems not to have known of the existence of the Spanish Commission, since he criticized the administration for failing to organize the study of the earthquake. He commented on the “shameful backward state of science we found in Spain” (Martínez y Aguirre 1885, p. 156). This was a common view of the state of science in Spain by

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Spanish scientists in the nineteenth century and early twentieth century (Rodríguez Carracido 1917), but in this case the criticism was not altogether warranted.

7. FROM THE EXPLOSIVE TO THE TECTONIC SOURCE OF EARTHQUAKES As in the case of the Lisbon earthquake, the study of the Andalusian earthquake was also the occasion for the discussion in Spain about the causes of earthquakes (Delgado-Marchal, 1999). Following ideas proposed by Charles Lyell (1797–1875) in his Principles of Geology (1830–1833), earthquakes began to be related to tectonic processes in the Earth’s crust, thereby abandoning the explosive theory during the nineteenth century (Oldroyd et al. 2007). This idea was present in the study of the Naples Earthquake of 1857 by Mallet, connecting the occurrence of earthquakes with changes in the Earth’s crust that result in dislocations and fractures, though still maintaining the idea of a volcanic explosive source. In 1875, Eduard Suess (1831–1914) also proposed that earthquakes occur along lines representing fractures or faults in the Earth’s crust. The term tectonic earthquake (tektonische Beben) began to be used in Germany around 1870. The idea that earthquakes are caused by movements on the Earth’s faults was further developed in the late nineteenth century by Josiah D. Whitney (1819–1896) and Grove K Gilbert (1843–1918), studying Californian earthquakes, and by Bunjiro Koto (1856–1935) studying earthquakes in Japan (Davison 1924, 1927; Howell 1990; Bolt 1993; Valone 1998). In Spain modern approach to the study of earthquakes began among naturalists in the nineteenth century. Josef Ponce de Leon (1753–1819), with the occasion of an earthquake in 1806 in the province of Granada, wrote a short work on the nature of earthquakes (Ponce de Leon 1806, Martín-Marfil et al. 1999, Delgado-Marchal 1999). He assigned the cause of earthquakes to the explosion of accumulated inflammable material within the Earth caused by an electrical discharge. He thus linked the explosive and the electrical theories. As a professor of chemistry, he thought that only chemistry “could illuminate this hidden phenomenon”. The earthquake of 1 July 1829, which practically destroyed the towns of Torrevieja and Guardamar in the province of Alicante, presented another opportunity for the presentation of studies about the nature of earthquakes. Lorenzo Arrazola (1795–1873), professor in the Universities of Valladolid and Madrid and later a Minister in the Spanish Government, published a work on the nature and effects of volcanoes and earthquakes (Arrazola 1829, Canales Martínez 1999). He tried to explain the cause of earthquakes by the joined effect of subterranean water, air and fire together with the action of electricity. José Antonio Ponzoa (1791–1865), professor of mathematics at Murcia and later also a minister, published after the earthquake of 1829 a lecture he had given in 1815 about the nature of earthquakes. He also presented an eclectic position of the explosive and electrical theories (Ponzoa 1829, Canales Martinez 1999).

In the report about the 1884 earthquake the Spanish Commission, after presenting different theories about the causes of earthquakes, attributed the earthquake to “an accidental expansion of gases and vapors accumulated in the Earth’s interior” (Fernández de Castro et al. 1885, p. 104). The Commission also noted the influence of subterranean water and a possible connection between earthquakes and atmospheric conditions. There had been a considerable fall in the atmospheric pressure prior to the earthquake. The Commission’s thinking was, in fact, still nearer to the explosive theory and old Aristotelian ideas than to the new tectonic theories. This was one of the points of friction with the French Commission, which upheld the tectonic theory and proposed that earthquakes are caused by dislocations in the layers that form the Earth. This was the reason for the French emphasis on the geology of the region in order to find the cause of the earthquake. Also the French Commission rejected any connection between the earthquake and atmospheric conditions. In its conclusions, the French Commission affirmed the relation between the earthquakes and the geological constitution of the region. Taramelli and Mercalli proposed that the earthquakes of southern Spain, like those in southern Italy and central Greece, were perimetrici earthquakes—that is, those surrounding a volcanic region. Mercalli had divided earthquakes into vulcanici, perimetrici, and tellurici (Davison 1924). He explained the causes of

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these perimetrici earthquakes as produced by the force of the internal magma in a region where the static conditions of the crust makes it impossible for an eruption to occur.

José Macpherson (1839–1902), one of the founders of modern geology in Spain, took the opportunity of this earthquake to expound the tectonic theory of earthquakes in a public lecture given in the Ateneo of Madrid in February 1885 (Macpherson 1885). He began by stating that the general causes of all phenomena on the Earth’s surface, such as orogenic and volcanic processes, are derived from the secular cooling and contracting of the Earth. The contracting Earth hypothesis, popular in the nineteenth century, was defended, among others, by Élie de Beaumont, James D. Dana (1813–1895) and Suess. According to this theory the contraction of the Earth produces the accommodation by the folding and faulting of the layered materials of the rigid crust, which can be continuous or sudden, as when earthquakes take place. According to Macpherson (1885), earthquakes occur when the stresses on the layers of the crust exceed a certain limit, causing them to break and their fragments to slip over each other, going either downward or upward. He then explained the Andalusian earthquake as being due to movement along the system of faults that bound the northern and southern limits of the mountains of Sierra Tejeda and Almijara. Martínez y Aguirre and his colleague Rafael García Álvarez (1828–1894), of the secondary School of Granada and one amongst the first to introduce Darwin’s theory of evolution in Spain, presented a similar explanation in terms of the contracting hypothesis, adding also the notion of the collapse of underground cavities (Martínez y Aguirre 1885, p. 159). Taramelli and Mercalli quoted the opinions of Macpherson, Martínez y Aguirre and García Álvarez and showed their disagreement with them. In their opinion the contraction hypothesis, even if correct, could not explain the occurrence of a large localized earthquake like the Andalusian one (Taramelli and Mercalli 1886, pp. 216–219).

8. THE FIRST SEISMOGRAPHIC STATIONS IN SPAIN

At the time of the Andalusian earthquake there were no seismological instruments installed in Spain. But shortly thereafter Mario Jona, an Austrian engineer working at the port of Malaga, installed three pendulums, which made possible the determination of the time of a quake by means of an electric contact. With these primitive instruments he was able to establish the time of a great number of aftershocks. Father Eusebio Caballero, of the Jesuit school in Malaga, also used similar pendulums to detect and time the occurrence of aftershocks. In its report the Spanish Commission regretted this backward situation, in contrast to the seismographic stations already in operation in Italy. In its opinion the lack of instrumentation had prevented the detection of foreshocks previous to the main earthquake, which could have given warning of its impending occurrence. The Commission therefore proposed the installation of at least eleven seismological observatories near the Mediterranean coast where earthquakes are frequent, at Huelva, Cadiz, Seville, Malaga, Almeria, Murcia, Cartagena, Alicante, Valencia, Barcelona and Gerona, linked to a central observatory in Madrid. The Commission claimed that the cost would not be large and that the Corp of Mining Engineers could be put in charge of them (Fernandez de Castro et al. 1885, p. 99).

The recommendation by the Spanish Commission for the installation of seismographic stations in Spain was not, however, very effective and the first seismograph was only installed by the Englishman John Milne (1850–1913) in 1897, at the Naval Observatory at San Fernando (Cadiz), as part of his world-wide network of stations with the support of the British Association for the Advancement of Science. Under the same programme, a second instrument was installed in the mines of Rio Tinto (Huelva) in 1898. In spite of the Commission’s recommendation, the Spanish Government did nothing at an official level. Thus it was the Jesuits who in 1902 installed a seismographic station in Granada, as part of the Observatory of Cartuja, founded in their Faculty of Philosophy and Theology, which had astronomical, meteorological, and geodynamic sections. Two years later, they installed a second seismographic station in Catalonia in the Ebro Observatory (at Roquetas, Tarragona in northeast Spain), mainly dedicated to solar–terrestrial interactions. By the beginning of the twentieth century the Jesuits had established

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forty-five seismographic stations in different parts of the world, as part of their network of some seventy-five observatories managed by them between 1825 and 1980 (Udías and Stauder 1996, Udías, 2003). A third seismographic station was installed in Spain in 1906 at the Fabra Astronomical Observatory, a private institution, near Barcelona. At that time nothing was yet done in Spain at an official level in the field of seismology.

The first proposal for the establishment an official seismological network (Servicio Sismológico Español) was put forward in 1906 by Eduardo Mier y Miura (1858–1917) of the Geographical Institute (Instituto Geográfico y Estadístico, IGE), after attending the third International Conference of Seismology in Berlin in 1905 (Anduaga 2010, pp. 45–55). The IGE had been founded in 1873. It changed its name to Instituto Geográfico Catastral (IGC) in 1925 and to the present name Instituto Geográfico Nacional (IGN) in 1977. This institution, mainly in charge of geodetic and cartographic work in Spain, also has sections of geophysics and astronomy. Its members are Geographical Engineers (Ingenieros Geógrafos). The plan proposed by the IGE in 1906 for the seismological network called for a central station in Toledo and five secondary stations near the coast. Three years passed before the first station of Toledo was inaugurated in 1909, twenty-five years after the occurrence of the earthquake that had motivated its installation (Payo and Gómez-Menor 1998). Three other stations of the network followed in Almeria (1911), Malaga (1913), and Alicante (1914). With only four stations the official seismological network was far from the original proposal of eleven stations and a central observatory, as advocated by the Spanish Commission in 1885.

From the work at the new seismographic stations there emerged the first generation of Spanish seismologists. Manuel M. Sanchez Navarro-Neumann (1867–1941), the Jesuit Director of the Cartuja Observatory, compiled the first modern catalogue of earthquakes of the Iberian peninsula and was the author of the first book about seismology in Spanish: Terremotos, sismógrafos y edificios (Earthquakes, Seismographs and Buildings) (1916). Vicente Inglada Ors (1879–1949), Director of the Toledo Station, introduced the developments of German theoretical seismology to Spain. He proposed (1927) an early method for the numerical determination of the hypocentres of nearby earthquakes and was the author of a number of studies about earthquakes in southern Spain. Alfonso Rey Pastor (1890–1959), Director of the Toledo and Alicante stations, was the first to publish a seismotectonic map of the Iberian Peninsula (Traits sismique de la peninsula Ibérique, 1927).

9. THE SPANISH DEEP EARTHQUAKE OF 1954 Early in the morning of the 29 March 1954, the recording needles of the Wiechert seismograph at Toledo were thrown off the scale, indicating the occurrence of a large earthquake in southern Spain, and it was thought it might have caused serious damage in the region (see Figure 6). News from the south, however, reported that only very moderate shaking had been felt and there was no appreciable damage. The earthquake of Magnitude 7.5 was felt over a large area of southern Spain and northern Africa, but intensities nowhere exceeded Grade V in the Mercalli scale (shaking felt by most people, light damage to some structures). Although a large magnitude earthquake it was hardly noticed by the public opinion. Local newspapers showed little interest in the earthquake (see Figure 7). It was only when information came in from the Bureau Central de Séismologie of Strasbourg and the U.S. Coast and Geodetic Survey of Washington that Spanish seismologists became aware of the extraordinary nature of the earthquake (Bonelli and Esteban-Carrasco 1957). When seismologists studied the seismograms of this quake, they were surprised to discover that its focus was located at a depth of 630 km (Frohlich 2006, pp. 21–25). This was unusual, since at that time no earthquakes were known to have taken place in Europe at such a large depth. The deepest ones at the Sicily–Calabrian arc only have depths of about 350 km. Seismologists around the world were interested in the occurrence of this event, and it also stimulated interest in seismology in Spain. At the time the occurrence of this unusually deep earthquake had no explanation. Later in the context of plate tectonics the earthquake pointed to a very deep and complex structure of the boundary between

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the Iberian block and the African plate. A detached lithospheric block, sunk to a depth of 630 km, has been proposed for the source of the shock, but even today the cause of this deep seismic activity remains an open question (Chung and Kanamori 1976, Buforn et al. 2011).

In Spain, the situation of the seismological stations at that time was practically the same as in 1914, except for the installation, about 1930, of new instruments of the Wiechert and Galitzin types. The national seismological network run by the IGC had added only one new station in 1951 in Logroño. The deep earthquake of 1954 brought attention to the need to modernize the instrumentation of the stations and establish better international relations. The IGC acquired new Askania–Hiller seismographs for its stations, which were installed between 1959 and 1962 in Alicante, Almeria, Malaga and Logroño. This proved to be a poor choice of instruments since their performance was not up to expectations.

The Spanish Civil War (1936–1939) caused a serious break in the work of Spain’s scientific institutions (Sánchez-Ron 1999, pp. 301–328) and the Second World War and the difficult post-War years made recovery difficult. This affected work in seismology as well as other branches of science (Anduaga 2009, pp. 231–247). At that time, work in seismology was limited to the IGC and the Jesuit seismological station of Cartuja. The IGC realized the need to open up seismological collaboration and training of its personnel at seismological centres outside Spain. In 1955, Alfonso López Arroyo (b. 1926), later Director of the Malaga Observatory, went to Saint Louis University (Missouri) to work on seismology under James B. Macelwane (1883–1956) and in 1960 and 1963 to the University of Uppsala (Sweden) with Marcus Båth (1916–2000). He was the first Spanish seismologist to be trained outside Spain. Gonzalo Payo (1931–2002), who in 1965 became Director of the Observatory of Toledo, also spent a year working with Båth at Uppsala. He later contributed some important work on the propagation of surface waves across the Iberian Peninsula (Payo 1965). José María Munuera (1909–1999), chief of the Spanish Seismological Service, established a fruitful collaboration with the United States, which helped the development of seismology in Spain. The American Government was interested in installing some seismographic stations in Spain as part of a 1960s worldwide cold-war programme of deploying stations with newly developed instrumentation with the purpose of monitoring underground nuclear explosions. The network consisted of 125 stations known as the World Wide Standard Seismographic Network (WWSSN). In Spain two stations were installed in Toledo and Malaga in 1962. Seismographs of similar type were also installed in the Ebro Observatory. Collaboration with American seismologists opened a new period in Spanish seismology.

The 1970s marked the beginning of a new period of seismological research in Spain. Universities, starting with Madrid, Barcelona and Granada, established research programmes in seismology. Other scientific institutions, like the Higher Council of Scientific Research (Consejo Superior de Investigaciones Científicas), the Geological Institute of Catalonia (Institut Geòlogic de Catalunya) and the Andalusian Geophysical Institute (Instituto Andaluz de Geofísica) also undertook seismological research. This constitutes a new chapter in the history of seismology in Spain.

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Figure 6. Recording of the 1954 deep earthquake at the station in Almería (Z Mainka) (Archivo Instituto Geográfico Nacional, Madrid).

Figure 7. The 1954 earthquake in the ABC newspaper of Seville of 25 March 1954 (“Yesterday an earthquake was recorded in several points of the peninsula and Africa. It was also felt in Seville”). There was no mention of damage in the news (Hemeroteca de ABC de Sevilla).

10. SUMMARY

As was the case in the general development of the science of seismology, the occurrence of large earthquakes was a catalyst for the progress of this science in Spain. We have selected the large earthquakes of 1755, 1884, and 1954 to exhibit the main lines of the early development of seismology in Spain—a chapter of the history of science in that country that has hitherto received little attention. As in other fields of science the development of seismology in Spain was behind the progress in Europe, North America, and Japan. The debate about the natural or supernatural character of the 1755 earthquake led to the consideration of its occurrence on purely rational grounds, opening the way to the scientific study of earthquakes. This marked the process of the progress of the Enlightenment ideas in Spain, which favoured the introduction of modern science. It was also the occasion for the introduction of modern ideas about the causes

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of earthquakes and the abandonment of the traditional Aristotelian doctrine still taught at Spanish universities. The explosive theory of the nature of earthquakes favoured by Newton and Buffon gained grounds among Spanish authors. Feijoo took the bold step of proposing an original electrical theory of earthquakes, although unknown to him, it had been already proposed, a few years before, by other authors outside Spain. During the nineteenth century Spanish naturalists made a synthesis of the explosive and electrical theories to account for the origin of earthquakes. The 1884 Andalusian earthquake was the subject of the first scientific study of a Spanish earthquake by international cooperation. The three commissions from Spain, France and Italy that were established to study it and assess the damage published lengthy reports. France and Italy were then at the front of seismological research. The visit of the two renowned seismologists, Mercalli and Fouqué, was an important factor in the introduction of modern seismology in Spain. Their studies contributed to the knowledge of the geology and seismicity of southern Spain and introduced the new ideas about the tectonic origin of earthquakes and the quantification of their effects. This earthquake revealed the need for the installation of seismographic stations, though it took years before it was implemented. Finally, the Spanish deep earthquake of 1954 generated a renewed interest in seismology in Spain in the difficult times after the Civil War. It marked the beginning of a renewed international collaboration of Spanish seismologists and helped the development of seismological research. Seismology certainly progressed in Spain during the 200 years between 1755 and 1954, but it was behind the developments of this science in other parts of the world.

ACKNOWLEDGEMENTS The author thanks Professor Greg McIntosh, who revised the English text and Professor Jesús I. Catalá Gorgues of the Universidad Cardenal Herrera CEU, Valencia, for valuable suggestions. The work was partly supported by the Ministerio de Ciencia y Tecnología (Spain), project CGL2010–19803–C03–01, and partly by the Universidad Complutense de Madrid, project BSCH–UCM, GR58–08, 910399.  

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