This is the probability that 27F will appear again

Today we commemorate a new anniversary of a fateful date in the history of Chile. Exactly 14 years ago, At 3:34 in the morning, a mega-earthquake shook the country, reaching a magnitude of Mw 8.8.

With a total duration of 2 minutes and 30 seconds a depth 30.1 km, This phenomenon affected the regions of Valparaíso, Metropolitana, O’Higgins, Maule, current Ñuble, Biobío and La Araucanía. A total of 525 people died and another 23 were missing, considering the subsequent tsunami that hit the nation’s coastline.

Taking into account the magnitude of the telluric event, the question arises as to how the affected area is currently doing. Geologically and seismologically speaking, What is the current situation at the location where 27F occurred? How likely is it to happen again?

Pablo Salucci, a geographer at the Catholic University and an academic at the University of San Sebastián, explains that the event known as 27F “corresponded to an interplate earthquake, which occurs from 500 km tear. long off the coast of the Biobío region (present-day Ñuble region), making it the second largest earthquake after the 1960 earthquake (9.5 Mw).

In addition to the impacts observed in cities, Coastal geography has undergone important changes, as it usually happens with mega-earthquakes recorded in our country. “Coastal areas have been observed to suffer from so-called ‘coseismic effects’, which correspond to changes in the Earth’s surface that occur during the event (landslides, cracks, liquefaction),” explains the geographer.

In this case, “the earthquake produced uplifts and subsidence (subsidence) of the coast, where the total uplift of the Arauco Peninsula was estimated at 2 meters, they change the morphology of the coast and seriously affect the coastal ecosystems. In addition, it caused the tide lines to recede, with a subsequent increase in beach area. At this moment, it is important to observe the transformative power of the landscape that these earthquakes can have in our country,” he adds.

Salucci explains that although the Gulf of Arauco, where the epicenter of the earthquake occurred, has several geological faults, none were connected to it. “After the time that has passed, The crust has already regrouped and we haven’t had any late shocks in recent years. A new seismic cycle has already begun in an area that has historically experienced several earthquakes. It could take hundreds of years for such a registration to be registered, although it would be possible in the short term around 6 MW“.

As the years pass, the size of the possible earthquake increases, warns the academician. “The probability of this happening is low because there is not enough stored energy. The segment of interest is the segment before Valparaíso, from Los Vilos to Pichile. All the conditions for a mega-earthquake are here. That could be anytime.”

Due to the current situation in the place New infrastructure was incorporated, linked to reconstruction plans promoted from the central level. “This highlights the river buffer parks built in Constitución and Pelluhue, works that will mitigate future local and distant tsunamis (like the one that occurred in 2011 in Japan) and reduce employment density in sectors that were severely damaged by tsunamis,” Salucci asserts .

“Although the evacuation routes and associated signage, which are in varying degrees of protection, have improved, Unfortunately, critical infrastructure such as firefighters and others in tsunami inundation areas, as well as homes, are still being observed.. In this sense, memory and continuous education are necessary, linked to the seismic reality that sooner or later will hit the sector again,” he adds.

Although the evidence shows that it takes 200 to 300 years to create this type of earthquake,”this It cannot leave us alone because due to our position in the Pacific (in front of the Ring of Fire) we can experience a distant field tsunami that can significantly affect our coastal settlements. We always have to be ready,” says Salucci.

Salucci believes that an interesting example is the case of the Chiloé earthquake. On December 25, 2016, a magnitude 7.6 earthquake occurred in the south of the island, in a segment that ruptured in a magnitude 60 earthquake. This measures how long it takes for the segments to start accumulating energy. In this case they were 56 years old cause a 7 Mw earthquake again.