Is your home earthquake proof? | Part 2

The “Norma de Construcción Sismorresistente: Parte General y Edificación (Ncsr-02)” Spanish Earthquake-Resistant Norm classifies buildings in accordance with their intended use and with the damage their destruction can cause, they are classified as:

Buildings moderately important.

Buildings with a negligible probability that their destruction during an earthquake may cause any casualties, disrupt a primary service, or cause significant economic damage. For example warehouses or agricultural buildings with access restricted to a small number of people.

Important buildings.

Buildings that if destroyed by an earthquake can cause casualties, disrupt services to the community, or cause significant financial loss, but their destruction do not interrupt an essential service to the community or may produce catastrophic effects. Residential buildings are catalogued here.


Particularly important buildings.

Buildings that if destroyed by an earthquake could disrupt essential service or lead to catastrophic effects and at least the following buildings are included:


Hospitals, health centres. Radio television, telephone and telegraph facilities. Buildings used for support personnel and equipment such as fire stations, police. Buildings used for basic services supplies such as water deposits, gas, fuel, pumping stations, distribution networks, electrical power etc.Large civil engineering structures as nuclear power plants or power stations, large dams and those that, may result in potential risk from their failure. Buildings classified by the local authorities as historic or artistic monuments.


The application of this Norm on the calculation of their structure is mandatory in all the “Important buildings” i.e. residential buildings, but depending on the region of Spain they are situated. Here in south east Spain the majority of municipalities fall under a zones with a seismic acceleration higher than 0,08g (g = to gravity) being that figure the limit for buildings to be calculated against earthquakes and include all “Particularly important buildings” and structures.


We also saw that this EMS scale divided into intensities, let us give a description of the effect each grade may cause.


Grade I: the shock is not perceived by human senses, being detected and recorded only by seismographs.


Grade II: the shock is perceptible only by some people while at rest, especially on upper floors of tall buildings.


Grade III: the shock is perceived by some people within buildings. The vibration perceived is similar to that caused by the passage of a light truck.


Grade IV: the earthquake is perceived by people inside buildings and some outside, but it is not scary. The vibration is comparable to that produced by the passage of a heavy truck. Windows, doors and dishes rattle. The furniture starts moving.


Grade V: The earthquake is felt by most people inside and outside of buildings. Some people instinctively start to run away. Animals get nervous.


Grade VI: The earthquake is felt by all people, inside and outside. Many people take to the streets in panic, some lose their balance. Animals run away. Crockery and glassware break, books fall from shelves, pictures move or fall from walls and unstable objects are overturned. Church bells toll by themselves. There are moderate damages in some constructions.


Grade VII:  Most people are terrified and run into the street. Many have difficulty keeping up. Vibrations are felt by people driving cars. Load bearing walls construction many suffer serious damage and some reinforced concrete buildings may be affected. Changes happen to the flow of springs and rivers. In some cases, well spring appears in new places and others disappear. Grade VIII: Fear and panic are wide spread, even in people driving cars. In some cases branches of trees are torn off. Furniture, including heavy furniture, move or are overturned. Hanging lamps are smashed against the ceilings due to the movement of the buildings. Many load bearing buildings are destroyed and some collapse. Reinforced concrete buildings many suffer serious damage and some are destroyed. Cracks appear on ground several centimetres wide.


Grade IX:  There is total panic. Most load bearing walls buildings will collapse. Many reinforced concrete buildings not design for earthquake will suffer heavy damage and some will collapse. Underground pipes will be partially broken. In some cases, railroad rails will curve and be out of service. Cracks up to 10 centimetres wide will appear on the ground. Rocks will fall from mountains in some case even avalanches of rocks. Many landslides will happen. Big waves could be seen in lakes and reservoirs.


The biggest earthquake recorded on earth.

Incidentally the biggest earthquake recorded on earth was in Chile in the city of Valdivia, the earthquake had a magnitude of 9.5. There were 2,000,000 people made homeless. Valdivia sank 4 metres below sea level and caused the eruption of the volcano Puyehue. The quake was felt across the southern hemispheres, a tsunami swept across the Pacific Ocean, reaching Hawaii and Japan.


Up to here we have had points of reference with earthquakes that have taken place before, from scale X on, there is a degree of speculative conjecture as to what may happen, even though scientist consider that the following may take place:


Grade X: Most load bearing buildings will collapse. Serious damage will be inflicted to reinforced concrete o steel buildings. Great damages may occur to dams, bridges, railways. Most underground pipes will break. Streets paving and road asphalt will form large waves. Cracks on the ground could form from a few centimetres to a meter wide. Landslides will occur on most mountains. New lakes will form.


Grade XI: Most constructions will suffer sever damaged or will collapsed. Damage will be caused to most major dams, bridges and railway lines. Most roads will be out of service. Most underground pipes will be destroyed. Ground will be significantly deformed by both land movements and rock falls. The skyline will change.


And for the big one……Grade XII: All structures and buildings are virtually destroyed or are severely damaged including those built underground. The topography would undergo great changes. Large cracks in the ground bigger than a metre will appear with significant horizontal and vertical displacements. Falling rocks and subsidence occur in most valleys some of them disappearing and transforming them in lakes new ones appearing. The skyline will change dramatically and probably the whole world.


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