Are we prepared for vertical evacuation in the event of a mega-earthquake and tsunami?

It is not known exactly when, but according to various scientists, We are in a period where a situation could repeat itself. mega earthquake like that of Valparaíso in 1730. About 9 degrees , Coastal cities are very likely to be exposed to a tsunami which will force the inhabitants take refuge in areas where water does not reach .

For that, There are two types of evacuations : the first is horizontal , where people should go —by the evacuation routes— to the high places , above 30 meters above sea level and as far from the coast as possible . However, many factors make it impossible for some residents to reach them before the wave hits.

In this way, the second alternative is considered, called vertical evacuation It’s made of enter a multi-story building and climb as high as possible .

“If you can’t go to a high area, climb to a higher floor or to the roof of a solid building “, says Senapred.

The previous one is a somewhat unknown measure, but useful for escaping a disaster when you don’t have the time or tools to reach a location quickly. safety zone .

But it’s not as simple as just going up any building, well, What if the structure was damaged by the earthquake before the water came? What if the janitors don’t let any civilians in to take shelter? Is the building made of the materials needed to withstand it? These are the answers from the experts.

There are several criteria to determine if a building can withstand a vertical evacuation. Jorge León, architect and principal researcher at the Research Center for Integrated Disaster Risk Management (CIGIDEN), says The third who managed to identify three groups.

The first is the urban criterion It is The building is well located in relation to the distribution of the population how many people there are, how easily accessible they are and whether they are easily identifiable.

The second is how the building will be used and whether its architectural design has the capacity and space to accommodate foreigners —not just the inhabitants—, if the stairs and corridors are wide enough and if there is a space with the necessary height.

And finally, The third group of requirements concerns the structure .

—Chilean buildings, those designed according to seismic standards, They have a great capacity for resistance The Chilean standard is still considered good, one of the best in the world, and preliminary studies and even previous experiences have shown us that they would also have the capacity to withstand the impact of a tsunami — assures León.

And that’s it, even if There is no construction standard to withstand a tsunami , The fact that a structure does not collapse in the event of a strong earthquake is already an indicator that it can serve as a shelter. in case of a disaster that could occur later, with sea water.

However, experts stress that if a structure is visibly damaged after an earthquake, it is better to move on and choose another construction.

—In a tsunami scenario, if we identify buildings of appropriate height, made of reinforced concrete and, hopefully, built after 2010 (when the seismic standard has improved), it is probably more advisable to evacuate vertically than to attempt a horizontal evacuation, because of the timing of the arrival of the water, which can be very risky — says the expert.

To the above, Cristian Cortez, structural engineer and CIGIDEN researcher adds, in conversation with LT that an ideal building to host this type of event is one whose first floor is clear . That is, there are no walls, only columns.

—The force that water exerts on a structure depends on the concrete surface that structure has. . So the smaller the contact area, the weaker the force will be,” he explains.

Cortez remembers the Illapel earthquake in Coquimbo in 2015, which registered 8.4 degrees. Then the tsunami arrived and the resistance of Chilean structures could be verified empirically.

—We have theories, studies, models, simulations… But in This earthquake, where the El Culebrón wetland is located, near the port of Coquimbo, caused tsunami flooding and, in this area, buildings were affected. . This showed that the water only generated non-structural damage, without any risk of collapse. In this sense, we have real proof that our structures, designed with seismic regulations, are still useful in the event of a subsequent tsunami,” the specialist explains to LT.

In addition, León does not fail to mention the international experience where this type of practice has already been implemented and used successfully, such as in the United States, Japan and Indonesia.

-In general, This is a policy that works well and provides a significant degree of security when properly planned and organized. —said the architect León.

This organization must therefore go hand in hand with all the competent authorities, the law and the people themselves, who must be educated and informed on how to evacuate vertically, identify a suitable building, among other elements.

At CIGIDEN, they are working on a project that seeks to establish more clearly the criteria that a building must meet and to be able to deliver them to the authorities and decision-makers to move towards the massive and systematic implementation of vertical evacuation.

— There is a whole question that will need to be explored concerning the vertical evacuation management model to be able to implement it . In Chile, there is an almost constitutional question, I would say, which concerns how, basically, someone guarantees access to private areas for evacuation in case of need — León emphasizes.

According to the stories he deals with, there have been cases where Some buildings did not allow non-residents to enter the premises to protect themselves .

“The fight against this disease is going to require a fairly systematic policy. Even what we mentioned in a document is that we should probably think about giving some kind of incentive or that a public body acquires part of a private building to guarantee access and not use it for housing – illustrates the architect.

Cortez adds that it will take a lot of communication to make this work.

—There are several topics that will have to be discussed with the rest of the people. Even from an interdisciplinary point of view, such as the point of view of sociology, of people’s behavior, because there are studies on mitigation measures that generate the opposite effect. We do not want the use of vertical evacuation to be taken lightly -said.

Who will be responsible for deciding how many people can enter a building? How will you do it? These are some of the questions the expert asks himself.

-I believe that The structures are capable of withstanding earthquake and tsunami but there are still many, many conversations.