Is your home earthquake proof? | Final part

Is it obligatory to apply the Spanish Seismic Norm (NCSR-02) to all new construction and buildings which are rehab or extended.

The architect may under his own responsibility apply other seismic criteria on his design, but the minimum standard shall be that of the Norm. In other words all new buildings or major reform projects must take into account the (NCSR-02) Seismic Norm as a minimum benchmark.

Costa Cálida and Costa Blanca as the most hazardous areas.

In the Norm there is a highly illustrative seismic map of Spain that shows Costa del Sol Costa Cálida and Costa Blanca as the most hazardous areas. These areas are really located approximately around the provinces of Granada, Malaga, Almería, Murcia and Alicante. The map also provides the so-called basic seismic acceleration (a characteristic value of the horizontal acceleration of ground surface) and a coefficient that takes into account the influence of different types of earthquakes envisage on each of these areas during a period of time.

In areas where the expected acceleration is very low, the regulation exempts seismic standards to be applied (the lowest seismic zones are located around the centre of Spain). Earthquake is a statistical phenomenon, and the mathematic formulae are unemotionally applied as it is applied on a horse to win the Grand National. The probabilities that an earthquake should happen in your neighbourhood depends greatly if you are in the areas I have mentioned above.

My personal opinion is that the Spanish Norm is very strict and does set a criteria, based on the intended use given to the building and the zone in which the building it is situated.

It doesn’t forbid the use of any structural material, but it establishes technical criteria for the design and calculation of the structures using those materials. The standard is more demanding for buildings used for transportation, communications, hospitals, administrative buildings and other facilities which hold essential services (water, electricity etc.), to ensure they can be used in emergencies and during a disaster.

All buildings designed under this Norm will endure an earthquake in better conditions than expected because in the calculations, we architects apply high safety coefficients which place the structure on to the side of security.

Spanish Nuclear power stations.

Regarding the Spanish nuclear plants, construction are governed by special regulations, and I am convince that they are in safe hands, but I am sure that after the Fukushima nuclear accident, new revision of the rules and protocols will take place not only in Spain but world wide, which will benefit us all. Although let me remind you that the real problem at Fukushima was not caused by the earthquake, but by the tsunami that followed it and inundated the plants disabling all safety services, specially the cooling pumps.

The last tsunami in the Mediterranean Sea occurs in 1755. Lisbon was devastated in part by an earthquake, which was followed by a tsunami with waves that reached 10 meters, according to testimonies of the time.

The seven nuclear plants in Spain are situated away from the sea and on the zone with the lowest seismic grades.

However I do belief in Murphy's Law, it is only a question of time, as we have seen in Japan. Catastrophic event occurs when no one suspect it. It is also true to say that there isn’t a facility in the world that can be said to be absolutely safe and it also true that any building can be made a bit safer and when one think it is very safe it can be made a little safer.

The cost of security

But is it really much more expensive to build following the Seismic Norm? I believe that obviously there is an extra expense in designing an structure taking into account the Norm but it is not that much if the structure is thought out from the initial concept design of the building. A symmetric form will help absorbing the whipping effect of a tremor more so than a building without symmetry and many times we are free to choose ay form in our design.

It seems that the attempt to reduce costs was the reason that hundreds of houses allegedly built to earthquake standards collapsed like sand castles after the 5.8 magnitude earthquake struck the Italian region of Abruzzo in April 2009. Two six-story buildings situated in practically on the same Via Campo di Fassa, in the town of L'Aquila, demonstrated how the application of the seismic rules and use of appropriate materials saved lives.

After the earthquake, one of the buildings remained standing, saving the lives of all the occupants. The other collapsed completely, killing 29 people. As reported later, many new buildings were constructed by mixing cement with unwashed sea sand, which did damage the foundations steel reinforcement due to salt corrosion.

However if all countries comply with the existing earthquake norms, deaths would fall drastically, as it has been demonstrated in Japan, the country with best designed buildings against quakes. The buildings constructed under Japan's strict regulations have withstood many earthquakes and have saved many lives. However Mother Nature seems to prove to us every now and then, who is in charge by sending new type of catastrophe for which we were not prepared.

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