The earthquake of ATARFE-ALBOLOTE
19th of April 1956
Introduction

As a phenomenon, earthquakes are as current and usual as any other natural phenomenon. The Earth’s tremors occur, albeit on a different timescale, in the same way as other phenomena such as rain, wind, snow hail, etc. If we analyze seismic activity globally, an earthquake occurs approximately every thirty seconds, which indicates a very high number of events during an entire year, and what is more, it is clear that not all of the regions of the Earth have the same number of tremors. Most of them, in spite of their great number, pass unnoticed by mankind but are recorded by modern instruments developed by researchers. Through these records we are able to compile data allowing the events to be studied, analyzed and investigated. Knowledge of these earthquakes has led to the development of the science of Seismology. Earthquakes which occurred a long time ago fall into the category of Historical Seismic activity since we lack the records necessary to study them and we have to use Archive documents and other printed sources. Studies using recorded information are relatively modern and few centres in the world have more than or come close to having a hundred years of operational experience.

The areas where earthquakes occur most commonly are the shores of the Mediterranean, the Pacific Rim, the Middle East, India, China and the Caribbean. Following an earthquake, we can observe the effects of the repeated earth tremors: epidemics, fires, the death of men and animals, economic losses especially of dwellings and the national heritage. Throughout the ages man has tried to explain these types of phenomena, and this has led to the creation of legends, rational explanations and the preparation of treatises. Pliny said that "where the Earth has trembled, it will tremble again". The Bible, Christianity and Islam attribute a divine explanation to earthquakes and link these kinds of event to the sins of mankind. This way of thinking lasted up to the nineteenth century during which rational and scientific explanations began to be attributed to earthquakes. One of the closest to us in terms of time and its importance was the earthquake we are studying here. Many people still remember those days when nature seemed to conspire against mankind.

The earthquake

The Albolote-Atarfe earthquake of 19 April 1956 is one of the most significant of the twentieth century in Spain, and it is in the destructive category together with the earthquake of 16 Jun 1910 in Adra, the Granada earthquakes of 1911 (Atarfe, Pinos Puente, el Jau, Láchar, Huetor Tajar and Granada), the earthquake of 5 July 1930 in Montilla, the earthquake of 5 March 1932 in Vícar (Almería), the earthquakes in the province of Jaén in 1951 –in Andújar, Bailén and Linares– and the earthquake of 9 June 1964 in Galera and Orce. The earthquake affected a wide area and its effects were studied by well-known researchers such as Father Antonio Due Rojo, Juan Sancho de San Román, Juan Bonelli Rubio, Luis Esteban Carrasco and most recently by Francisco Vidal Sánchez.

With slight differences between their accounts, all of them tell us that the tremor began at 18 h. 38 m. and 53 s. (GMT) and caused panic throughout the area located between Sierra Elvira and Granada causing alarm in almost all of the province. The next day the newspapers said that the villages of Atarfe and Albolote were ruined and that Santa Fe, Maracena and some districts in the capital were seriously affected. Help was sought from the Government. The coordinates of the epicentre were 37.26 N, 3.73 W, depth 6±3 Km, magnitude 5.0 and intensity VIII in Albolote and Atarfe. 7 people were killed directly and 5 by a landslide close to El Beiro in Granada due to the collapse of a cave situated next to the road to Casería de Montijo. As a consequence of the earthquake and the effects of the rain a huge crack was made in the hillside. At two o'clock in the afternoon of 20 April some 5.000 m3 of earth slipped. A couple with 3 children lived in the cave and all of them died. Another landslide at the same place in 1945 caused 4 deaths. Additionally, it is said that there were some 40 people injured, several hundreds of dwellings destroyed, many others rendered uninhabitable, serious interruptions to supplies and material damages to the tune of 20 million pesetas (of the day). One of the injured died on the 25th. Pastor gives us a higher number of deaths, putting the numbers at 13 deaths and 73 injured. This damage was increased by the numerous aftershocks which continued for several weeks. Father Due (director at the time of the mapCartuja Observatory) informs us that the epicentre was located between Albolote and Atarfe, an area without villages or cultivation and, as a result, the degree of damage was not further increased. level VII was reached in a radius of 10 km [image 1] meaning that it reached the capital and some twenty villages in the Vega area. It had a relatively shallow focal depth.

Father Due describes the earthquake recounting that he was on the second floor of the Faculty of Theology and that it lasted some four seconds, that it was a violent event, causing cracks in the joints of walls and windows and in plaster rendering, caused objects to fall, stopped clocks etc. Following his investigations he reports that in Albolote walls in an East-West orientation suffered most damage, there were cracks in the columns of the church, a rockslide in Sierra Elvira, chimneys and cornices were destroyed and fell down trees were moved, there was a general subterranean noise which was noted in villages which were quite far away. He reports strange phenomena described by people such as a draught of air, fire and rocks from the drover’s road known as Tajo Colorado which appeared to come from Raja Santa, although a group of speleologists from Granada denied this in the newspapers. Father Due carried out other inquiries on the occasion of the earthquake which occurred on 4 June 1955 affecting Atarfe and causing material damages. Some people say that they saw a brilliant reddish yellow globe in the early hours of the morning. He distinguishes between the buildings which were well and poorly constructed, and talks of European and non-European houses, cohesion or joints of their shared elements (beams, partition walls, ceiling fittings), materials used, joints of stones in masonry, bricks fixed with mortar, etc.

Pastor attributes the destruction to the poor quality of the building work and to the poor quality of the materials used. Having analysed the sites affected, he is of the opinion that the official statistics were exaggerated in claiming that 30% of the dwellings had been practically destroyed, that 60% in Albolote had significant damage, 5% were destroyed and that in the case of Atarfe 40% had significant damage. This author says that he had not performed an inventory but believes that the surveys and documents are somewhat exaggerated. He also speaks about the landslides which took place in the Tajo Colorado in the immediate vicinity of Sierra Elvira and attributes them to the poor drainage of the quarry and the instability of the blocks of stone.

The aftershocks were studied by Father Due beginning with the one which occurred at 20 h. 0 m. and 28 s. and, given its proximity to the Observatory, it was difficult to record since the speed of rotation of the cylinders was one cm per minute. The aftershocks came one after the other. the most significant ones were recorded between 19 and 30 April and the first 8 days of May. Several tremors of different degrees of strength occurred on some days. He studied and recorded 116 significant aftershocks.

Villages affected and description of damage

The studies carried out by D.J Sancho de San Román, J. Bonelli and L. Esteban mean that we have accurate knowledge about the impact of the earthquake on the most seriously affected villages. In summary, these were as follow:

photo1.- Atarfe. Village of 8,000 inhabitants and 1,500 houses. Loose objects fell as well as some furniture. Buildings in good condition were damaged and 600 were left with repairable cracks, 600 with significant damage, 200 were ruined and 10 destroyed. Some facades collapsed facing West, walls next to the railway station were ruined [image 2]. The effects of the earthquake can be seen clearly in a marble slab factory [image 3] "Mármoles photoPrieto-Moreno Ruiz, S. A." [image 4], situated in front of the village next to the Granada road. A transformer house received cracks in its four brick walls. At the epicentre, people said that they saw light-related phenomena including the lights.

2.- Albolote. Village of 5,000 inhabitants and between 850-900 houses. Objects fell to the floor at distances of up to one metre from their original position better constructed buildings had cracks which were in some cases significant. buildings of lower quality were rendered unusable and others were destroyed. 350 houses were left with repairable cracks, 300 with significant damage and uninhabitable,50 were ruined and 7 destroyed. The facade of the Town Hall lost a crest with the village’s coat of arms. The church lost part of the eaves and its tower had notable cracking. Many dwellings lost their roofs.

We know that there were 5 deaths in Albolote and Atarfe and more than 60 injured as well as huge economic losses arising from material damages. The information is sometimes contradictory since the articles by specialists and those which appeared in the newspapers did not completely agree with each other.

3.- Granada. The strong earthquake made an unforgettable impression on those who felt it; its intensity was clearly felt, shaking everyone who was in the street, and there was general panic. Fallen objects, destroyed crockery, pendulum clocks stopped, the stone cross fell in the Church of the Sagrado Corazón and a stone crest from the Audiencia (court building). Buildings in good condition only suffered cracks. More poorly constructed buildings such as those in the Albaicín were seriously affected. Generally, in this district of Granada, 10% of the houses were evacuated and 50% suffered cracking. Some dwellings were ruined. There were two deaths in the capital and several injured. The clocks in the Cartuja Observatory stopped, seismographs broke down and cracks appeared in the rotunda of the building. In the city are still many people today who remember this earthquake and talk of the effects on the tram tracks, of how the streets moved as if they were small waves, etc.

4.- Maracena. Village of 4,000 inhabitants and 900 houses. Loose objects fell and many buildings were affected, one made from mud walls was destroyed. in summary, there were 700 houses with slight damage, 150 with significant damage and 10 ruined. The upper floor of some buildings collapsed.

5.- Santa Fe. Village of 11,000 inhabitants and 2,000 houses. All loose objects fell and many chimney parts. Generally, 50% of the buildings experienced cracking and slight damage. The damage was reported by the Town Council as being 70 dwellings with significant damage and 15 ruined. The Church had significant damage, the portico was cracked as was a significant part of the central nave.

6.- At the Cubillas reservoir, workers on the dam staggered. The flagpole of a tower which submerged beneath a depth of 17 metres and with 15 cm above the water oscillated, causing concentric waves to appear on the water. A worker recounts how, before the earthquake, he heard a boom which came from the South. in a small village next to the reservoir everybody went out onto the streets and cracks appeared on the dwellings.

7.- Peligros. there was general alarm, objects fell and some 400 dwellings were affected although only slightly since only 50 of them had significant cracks and it was necessary to evacuate another 7 houses which were in danger of collapse.

8.- Pinos Puente. 2,000 houses, everybody went out onto the street. The Town Council recorded 12 houses with significant damage and the majority of these had slight cracking, parts of some chimneys fell. The aftershocks of the earthquake were not felt by everyone.

9.- Melicena. Village of 1,100 inhabitants and some 200 houses. objects fell, many buildings experienced slight cracking and 4 of these had significant damage while another was ruined. Here, all of the aftershocks were felt.

10.- Purchil. Village of 1,600 inhabitants and 220 houses. Very similar to Melicena.

11.- Churriana de la Vega. General alarm, poor quality buildings were affected and 5 of these experienced significant damage. The most significant aftershocks were also felt.

12.- Armilla. Everybody was shocked and went out onto the street, objects fell, many buildings were cracked and some mud corrals were affected with pieces of mud walls falling. The aftershocks were felt.

13.- Pulianas. Village of 1,600 inhabitants and some 400 houses. Everyone went out onto the street and many buildings suffered slight cracking although considerable damage to 12 houses was noted and 7 were left half-ruined. The aftershocks were also felt.

14.- Güevéjar. Village of 1,100 inhabitants and some 250 houses. General alarm, many buildings with slight cracking and 5 of these had significant damage.The aftershocks were felt.

The Cartuja Observatory recorded the aftershocks which occurred as a result of the main earthquake. on the 19th itself, three aftershocks were felt. these were level V in Albolote and level III in Granada. On the 20th, 15 aftershocks were felt which reached level III in Granada. On the 21st, 7 aftershocks were felt and 24 were felt on the 22nd which were rated level IV in Granada. Father Due informs us that many of these were felt only slightly but that the people, who were highly sensitised to them, were alarmed. Aftershocks continued with 8 on the 23rd and 9 on the 24th 3 on the 25th, 1 on the 26th giving a total number of 58 level I, 7 level II, 4 level III, 1 level IV, 1 level V and 1 level VII. There were 2 more on the 28th, 13 on the 29th and 3 on the 30th. Some of these reached level IV. The aftershocks continued until the end of June during which small earthquake swarms were recorded.

In order to locate the epicentre, magnitude and energy, an analytical study was performed using data from the Cartuja, Málaga, Toledo, Alicante, Lisbon and Tortosa observatories. After careful examination of the data the epicentre was identified as right next to Atarfe. The area is well-known and belongs to the Granada seismic area whose plain is crossed by the Genil river. The huge seismic activity in the area is due to a contact zone between the Subettic and Penibetic mountain ranges (according to Due and others). This earthquake was felt in a wide area as can be appreciated from the map of isosists prepared by J.Bonelli and L. Esteban Carrasco, which appears next to some photographs from the time.

Finally, we can indicate that this earthquake had a moderate magnitude, and produced greater effects than those expected from this type of event. The reason for this greater amount of damage may be due to several factors which have already been mentioned: the poor quality of construction and amplification effects from the type of ground found in the Granada plain. This earthquake ought to serve to warn us about future harmful events, because many of the effects of earthquakes today can be avoided.

©2003 Instituto Andaluz de Geofísica || design ©2003 M.B. van Roode