Spanish building sector professionals are not still aware of the fact that Spain is a seismic country. Urban regulations determine a building’s volume enclosure without any seismic resistant design planning. They consider earthquakes as acting on single pieces of the system: buildings, rather than on the real seismic scenery: the city.
Worldwide, seismic building codes are written for engineering application, rarely accompanied by guidelines related to architectural or urban features, even modern cities enforce the use of certain irregular building configurations such as set-backs, soft first stories, adjacencies, etc (1).
Our modern lifestyle also means an increase of movement and speed; maybe we are now living on a non seismic area, but sooner or later, be it working, visiting, enjoying holidays, or otherwise, we will put our feet down on a seismic location. Are we really ready to do it? The answer is NO! L'Aquila and Lorca are witnesses to it.
Urban regulations in cities located in seismic zones, as Lorca is in Spain, usually do not include special seismic provisions, and are just the same as those located in non-seismic-prone areas. The NCSE02 code needs urgent revision: nine people died in Lorca, none of them due to structural collapses. Geotechnical matters such as the influence of local ground amplification should be reconsidered. Buildings with reinforced concrete structures but with set-backs, short columns, ground soft story, or incorrect anchoring of the non-structural elements, are examples of existing architectural configurations unsuitable for a correct seismic behaviour, and lots of cities worldwide are in the same situation. The earthquake that ravaged the Italian town l’Aquila evidenced that other European areas share the same risks.
|SANTA MARIA DE LAS HUERTAS SANCTUARY SERIOUSLY DAMAGED|
Actions should be taken in order to prevent similar effects in historical places with the same tectonic situation: Granada, Córdoba, Murcia, Alicante, Torrevieja..., which are potentially laying on the same risks: closer active faults, on grounds capable of doubling or even tripling the power of seismic waves.
|SANTA MARIA DE LAS HUERTAS SANCTUARY|
LORCA: THE MORE DENSE BAROQUE CONCENTRATION IN EUROPE, THE WORST CULTURAL HERITAGE DISASTER IN EUROPE SINCE THE 1997 EARTHQUAKE THAT STRUCK ASSISI IN ITALY
3. PEOPLE IN EUROPE ARE NOT TRAINED FOR SEISMIC EVENTS
|ARE PEOPLE IN EUROPE PREPARED ?|
|THE ANSWER IS: NO!|
NCSE 02 CODE has proved to be very effective regarding structural elements, but needs to be revised and completed, in reference to: Constructive non-structural elements, such as, parapets, cornices, installations, partitions and others: there is a lot to do regarding their design, location, anchorage, flexibility, etc. There is also an obvious need for reinforcing masonry walls, either made of bricks or of stone in those places where they are traditionally used. Local seismotectonic zoning is required, above all in zones where it is well known that seisms of the L’Aquila or Lorca type could happen in the future. New maps are required, as well as new approaches to the response spectrums from waves generated by the activity of shallow or superficial faults. It is urgent too, to revise the values of the contribution coefficient k after the experience in Lorca.
An increase of the basic acceleration values of the zones close to active faults is needed, especially in towns in line with the ones already identified with recent activity, and in the future, with those to be discovered. Major investigation, study and consideration of all the layers of the ground affected by foundations which may receive seismic waves is needed. The code classification in types I, II, III and IV is too vague and indeterminate to prevent structural damage due to geotechnical reasons.
Real geotechnical effects should be considered, revising the C coefficient associated to the ground. It is not enough to quote the possibility of liquefaction of granular soils, there is a wide range of deflections not considered in NCSE 02, such as collapses, densifications, reactivation of consolidations, etc., either in soil or in rock. Part of the new text to include as an extension of the in force code should have a geotechnical and geomechanical character according to the effects on buildings and infrastructures.
The appearance of new seismic zones should also bring about the exigence to adapt, as far as possible, the existing buildings to this new code. The Spanish Technical Building Code (CTE) included two important new concepts: the need to guarantee the safety requirements of structures, not only in the design phase but also during the execution phase, and while the building is in use. Also, it underlines the requirement of maintaining buildings properly in order to guarantee their performance and behaviour during their useful life.
This essential requirement is very important for seismic-resistant structures of existent buildings, that could have been designed complying with former codes. It is absolutely necessary to extend the Technical Buildings Inspection (ITE), already in force in many cities in Spain, to the whole country, with a special emphasis upon those structures in high seism risk areas. That would be the best option to reach our goals.
6. THE LESSONS LEARNT
In Spain, we have the first opportunity to apply the content of the NCSE02 article 1.3.3 after being classified VII-VIII, in such an extended area. The content is this: “...after a high intensity seism, a report of every construction located in areas with intensity equal o higher than VII (EMS scale) should be drafted, in order to analyze the consequences of the earthquake on it, as well as to determine the kind of measures to be taken in relationship. The author of the report should be the technical expert responsible for the maintenance, or if there was not one, the proprietor or legal owner of the construction...”.
Actions must be taken in order to raise public awareness. It is essential to raise the awareness of the population in general, especially the building sector, regarding the existence of areas highly vulnerable to earthquakes in the Spanish geography. The time has come to determine the preventive actions to be adopted as well as to plan all the procedures to follow in case of a high magnitude seism’s striking. These two should be the main objectives to be promoted by the administration, as well as the transmission of a clear message: Spain is a country with seismicity capable of killing and injuring people, seriously damaging buildings, infrastructures or heritage, or even paralyzing the whole economic activity of the second largest region in the country.
|LEARNING TO SURVIVE|
And, of course, people's behaviour before, meanwhile and after a seismic event. A minimun seismic culture correctly trained will be enough for an implementation of autoprotection philosophy, and a benefit for both the individual and community, and most of all, it will save lots of lives across Europe. A necessary lesson to be learnt from childhood. Spanish, and almost all European people are illiterate in this regard. So we technicians, must call our neighbors to awareness, especially after the l’Aquila and Lorca events: Let's go Europe...!