How is Chile preparing for the next major earthquake and tsunami?

The geographical conditions in which Chile is located make it a highly seismic territory, with more than 20 tremors of magnitude greater than 3.0 per day, according to the National Seismology Center, being a problem historically linked to national reality.

However, in the collective memory there are those events that, with magnitudes far greater than those that are the protagonists of the daily work, have meant an emergency, with some earthquake be able to bring one later tsunami .

These two threats were at the center of a recent seminar which brought together authorities and experts, under the title of Preparing for the Next Great Earthquake and Tsunami in Metropolitan Chile: Advances in Science, Institutions, and the Community .

The event was organized by the Disaster Prevention and Response Service (Senapred) the Hydrographic and Oceanographic Service of the Navy (SHOA ), the National Seismology Center (CSN ) and the CYCLO Millennium Nucleus associated with the Austral University, the University of Concepción and the Pontificia Universidad Católica de Valparaíso.

One of the speakers, Marco Cisternas, a researcher at the CYCLO Millennium Nucleus, spoke of the sustained interest over time in the analysis of historically recorded telluric movements, the data of which allow the study of possible future emergencies.

Regarding his investigative work, he highlighted the discoveries of deposits that preceded the earthquake of 1730, where It has been concluded that large tsunamis in metropolitan Chile occur every 200 to 600 years. . “We are going to celebrate the 300th anniversary of 1730 and that is why we are concerned “, he commented.

Before the analysis of said data, Sergio Barrientos, director of the National Seismology Center, explained that there is an instrumental record that reports from the late 1800s, while previous events are estimated based on the study of letters and other data of the time. .

—The summary of the seismicity of Chile is that these earthquakes of magnitude 8, according to the history of the last 450 years, we have an earthquake of magnitude 8 or more every 12 or 15 years or so . If we can see what the probability of an earthquake of magnitude 7.8 or greater is, since the Illapel earthquake of 2015 eight years have passed, it is about 60% that a earthquake will occur in part of Chile.

When asked how information is currently managed during an emergency, the director of the CSN detailed:

—To be able to react quickly to the possibility that an earthquake could generate a tsunami is that We established this protocol with SHOA and Senapred . SHOA feeds on a number of informants from around the world. We have the agreement to inform Senapred and SHOA of the location and size of the earthquake within five minutes, so that they can take the corresponding measures.

In this line, when defining each land on national soil, it is necessary to analyze its level of exposure that it could present during an earthquake and the possibility of suffering a tsunami, depending on whether it translates by changes such as subsidence or coastal upheaval. .

In this regard, Daniel Melnick, director of the Millennium CYCLO nucleus, spoke about the Chilean database of active faults (CHAF), public database of active and potentially active defects, available on the web failasactivas.cl .

—In Valparaíso we have several fairly large fallas , which have not been extensively studied. We have them as probably active faults, we need to investigate them further, between Valparaíso and San Antonio and could be activated during the next 1730 .

In this context, an interactive consultation site has also been activated, which contains models of threat, danger, crustal failures and information of interest to the community, in the CYCLO seismic portal .

Turning to the construction level, Fernando Yáñez of the University of Chile, director of IDIEM, pointed out that earthquakes have historically determined the functioning of Chilean engineering over the past 80 years, presenting a disturbing challenge. to consider :

—Talca (1928), Chillán (1939), Valdivia (1960), Algarrobo (1985) and Constitución (2010). These earthquakes occurred on Saturday or Sunday. The one in Chillán, which was on a Tuesday, happened around 12 p.m. This brings us to a conclusion Chileans have no experience of what an earthquake is on a working day when we are all in the office and the children are in school and kindergarten, when the traffic lights and lines are not working .

Regarding the tsunami risk analysis that can be positioned after an earthquake, Matías Carvajal, researcher at the CYCLO Millennium Nucleus and professor at the Pontificia Universidad Católica de Valparaíso, highlighted the main challenge when reacting to a emergency :

—With each earthquake, the seismic standard is reinforced. In my opinion the best we have in the world and that’s why people from other countries come to learn from here. But not in the tsunami, and one of the reasons is that we don’t have that experience . Earthquakes are more frequent than large tsunamis and this, from a learning point of view, is a problem .

Considering the possibility of a seismic event that results in a tsunami, the expert revealed that the conditions are favorable for its next appearance:

Geological records tell us that the tsunamis in the central zone of Chile are repeated every 200 to 600 years. On the other hand, historical records show us that the last great tsunami occurred 300 years ago, in 1730. . Modern records and scientific analyzes suggest that there is enough energy for the next earthquake to generate a large tsunami. This does not mean that the next earthquake will produce a large tsunami, but there is the tsunamigenic potential to generate one at any time. Finally, and most importantly, it is essential that we review evacuation plans.

In this respect, the 1730 earthquake has become an important point of study, given its intensity and the reported differences from other such events. With this approach, Carvajal said the following:

—A scientific question tries to understand why the effects of the 1730 earthquake were so different from those of 1822, 1906 and 1985. Why did one generate a large tsunami and not lift the coastline and the others generated small tsunamis and lifted the coast a lot? With current knowledge, science and observations, we understand that when an earthquake occurs, the crust deforms and it depends on where the energy is released. If the earthquake occurs deeper, the coast will rise and the tsunami will be smaller. If the earthquake occurs in the superficial area, under the sea, the seabed will rise and the tsunami will be larger. .

In this regard, scientists are focused on expecting an event of similar proportions to the 1730 earthquake, given the number of years that have passed since then.

—When we do analyzes and try to estimate where the energy was released in Chile, we see the energy released by the earthquakes of 2010, 2015, 1985, 1906, and 1922. The earthquake area of 1730 worries us (…) What we are sure of is that a tsunami like the one in 1730 will happen one day. I think there is a worldwide consensus that where there are large earthquakes, they repeat themselves. When? The truth we don’t know .

Regarding the threat of a tsunami, Patricio Catalán of the Technical University Federico Santa María and a researcher from Cigiden agree that collective preparedness is lower in the face of a tsunami, compared to the level usual during living earthquakes . However, he also clarified that a tsunami is not necessarily a destructive event, where lesser intensity tidal waves have occurred which are still considered as such. “They’re much more common than you might think,” he said.

-What have we learned? Just as earthquakes gave us the opportunity to improve the seismic standard, we tried to take advantage of them with the maximum possible responsibility (…) In 2010, it was a systemic warning failure, but many people, especially from the affected coastal areas, He responded naturally, since there were ex-Onemi and SHOA preparation campaigns.

This is why the researcher has clarified one of the main myths shared during the analysis of a possible tsunami. “This idea that the sea had to be collected because a tsunami is coming is fine, but if it’s not collected, that doesn’t mean it’s not coming. . We cannot go to the coast to look and say ‘we are saved’, mistake”, he expressed.

Before an event that surprises the inhabitants realizando sus labores en horario hábil, una de las anxieties considera la evacuación, donde Alejandra Gubler, investigadora de Cigiden, detalló el principal defio a la hora de considerar a los niños, que en dichas condiciones, estarían in progress. In this regard, an evacuation drill was carried out in educational institutions in Viña del Mar and Valparaíso to analyze the results:

—With these data, let’s put ourselves in the situation of what would happen if a tsunami like that of 1730 occurred off Valparaíso. The important thing here is that there is a time difference of up to 7 minutes between the first and the last student who starts to evacuate. It can take us 7 minutes to empty the school (…) A time difference of five minutes can go from no pupils concerned to 100% of pupils concerned. The messages here are: the importance of drills and evacuation plans.

In this scenario, the possibility of an event that does not give time to go to a distant place is also considered, for which the expert raises the need to deepen the use of vertical discharge . “Today is the second option. Many of us believe that in some cases it is the only option ”.

Remember that Senapred has evacuation plans for different parts of the country, to be taken into account in the event of a tsunami, which are available in website .

Review the complete presentation of the seminar through the following video: