Researchers of the UGR analyse historical earthquakes to design risk maps to prevent future damages
nächste Meldung
27.10.2006
Just a few months ago a tsunami devastated the coast of Indonesia and left more than 190,000 people dead.

The lack of prevention measures and the ignorance of the real risks in an area with such seismic activity were some of the factors that increased the effects of the seaquake. To avoid similar events in future in the South of Spain, a research team of the University of Granada, in collaboration with Italian scientists, has set a project that has analysed the epicentres of the earthquakes happened in the past to determine the risks they could cause in future.

Until the moment, nobody knew the exact point where the disasters started, like the earthquake of Alhama in 1884 or that of Malaga in 1680, as the seismic stations that record the earthquakes and send the signal to the observatories to determine their localization did not start to work all-out until the beginning of the 20th century. According to the geo-physicist and professor of the UGR [http://www.ugr.es] Jesús Ibáñez Godoy, “the only trace that remains of historical earthquakes is their capacity for destruction, but in most cases we do not know their epicentre, a very important data if we take into account that they could happen again in future with the same intensity and in the same place”.

In this sense, Ibañez points out that very often the epicentre of the earthquake was not in the devastated area –this is the case of Alhama and of the earthquake that destroyed Lisbon in 1755 whose centre was in Cape San Vicente- but in a nearby area that due to the absence of population did not suffer the effects so much. But, several centuries later, such areas, where there were movements of six degrees in the Richter scale, could be inhabited, and therefore it is so important to determine “where the earthquakes originated”.

Location

The method used by geophysicists of Granada to locate the epicentre of the seismic movements that took place several centuries ago has been the distribution by areas through a mathematical technique designed by them of the areas where the damages occurred to locate from there where the epicentre was.

The data extracted from this work are very useful to prepare risk maps. They will take into account not only the areas destroyed by the earthquake, but also the place where it originated and, therefore, the most liable to suffer damages in future. But this new contribution will not only be useful to get to know something more about the seismic past of the south of Spain but also to “carry out prevention measures that consider feasible construction formulas, edifications in compacted lands r the exact location of the areas that run higher risks in future to avoid major damage”, Ibáñez says.

Antonio Marín Ruiz | Quelle: alphagalileo
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Researchers of the UGR apply the method of acoustic emission to building diagnose, restoration and maintenance
nächste Meldung
27.10.2006
Although their voice is imperceptible, even stones scream when they are damaged. They emit an ultrasound that reveals the state of health of the building or construction they support and they can even tell where the damage is and what can happen in future if we do not deal with the problem.

A research team of the University School of Technical Architecture of the University of Granada [http://www.ugr.es], supervised by professor Antolino Gallego Molina is in charge since several years ago of listening to the laments of the materials using a technique, called acoustic emission, that auscultates the structural elements to get to know what happens inside from the emitted ultrasound.

This system can find out from an imperceptible fissure for the human eye to other damage by placing piezoelectric sensors that pick up the ultrasounds and send them afterwards to a computer system of information processing whose results can help to diagnose, restore and maintain any architectural collection.

The researchers, who are applying this technique in the field of Civil Engineering and construction, have only carried out laboratory tests until the moment, but their contacts with companies of construction materials will make their expansion to other problems of interest possible “before long”, according to professor Gallego, who adds that, although the acoustic emission technique can be used in diverse studies, his team will focus on two specific fields “fibre concrete quality control, especially used to supply uniform efforts with equal performance in all directions and avoid fragile fracture, such as in large elements, paving or tunnel or slope coating, and on the quality and functionality analysis of the mortars used to restore historical buildings”.

The professor of the Department of Applied Physics of the UGR [http://www.ugr.es], who works in collaboration with professors of materials and construction of the Department of Architectural Constructions and physicists of the University of Jaen, explains that, in the case of fibre concrete, (reinforced with steel or glass fibres, instead of the traditional steel bars) “is practically impossible” to do a fine quality control with the existing systems, as it is a material whose functionality can not be measured because it takes more or less time to brake after conventional tests with loading machines. Therefore, the use of the technique of acoustic emission would be advisable in these cases when ultrasound can reveal what is happening inside the material.

As regards quality analysis of mortars in restoration processes, Gallego says that in many cases, when new materials are added to restore a building, there are adhesion problems besides construction problems. It is very important considering that such adherence capacity guarantees the future maintenance of the recovered area. In this case, the technique of acoustic emission could also be promising to assess such adherence and, therefore, to determine if such adhesion will end up giving way or not.

Scarce presence in Spain

Despite the advantages of this method, its implementation in Spain is still very scarce. According to the physicist, only a private company located in Madrid is developing works with the technique of acoustic emission and the majority of them outside the country, specially set aside for corrosion detection in oil tanks and by-products. However, countries like the United States, Germany, England, France, Argentina, Brazil or Japan use that system in multiple areas from bridge vigilance to guarantee their security or the diagnose of historical buildings to earthquake prevention or the study of materials that compose oil and gas drums to prevent them from breaking, with the consequent problems for the economy and the environment.

In this sense, Gallego Molina points out that many of these applications should be developed here to guarantee the safety of all types of constructions such as bridges, port complexes or storage systems like the oil drums used in the oil mills of olive provinces like Granada, Jaen and Cordoba.

On the other hand, the supervisor of the research project also demands the organization of training courses, more attention on the part of the Spanish Association for Non-Destructive Tests, as there are not specialized experts in this field, and a major implication on the part of the Spanish System for Research, Development and Innovation.

Antonio Marín Ruiz | Quelle: alphagalileo
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