More than 15 years after the earthquake of February 27th: how the seismic building code in Chile has changed with the new 2026 update.

Sixteen years have passed since the earthquake of 2010, also known as 27F. It was Saturday, February 27th, at 3:34 AM, when an earthquake of magnitude 8.8 struck the central region of Chile. It is considered the second-strongest earthquake in the country's history and the eighth worldwide. According to official data, it lasted 4 minutes in areas near the epicenter, located off the coast of the Ñuble (formerly Biobío) region. In Santiago, the shaking lasted for more than 2 minutes. The affected regions were Valparaíso, Metropolitan, O’Higgins, Maule, Biobío, and La Araucanía, where approximately 80% of the country's population resides. There were 525 fatalities, 500,000 homes suffered severe damage, 2 million people were affected, and several old buildings were completely destroyed. Despite this, "the 27F demonstrated that Chile had a very robust seismic engineering, especially in terms of protecting lives and preventing collapses," Rodrigo Astroza, Dean of the Faculty of Engineering and Applied Sciences at the University of the Andes, told La Tercera. More than 15 years after the 27F earthquake: how has the seismic standard changed in Chile with the new 2026 update? The figures could have been even more devastating in terms of structural damage, had it not been for the seismic regulations, which at the time were quite advanced. However, the disaster also "revealed some shortcomings" that the new regulations, updated for 2026 and based on the Japanese model, take into account. What failed in the seismic regulations of 27F? The seismic regulations in force at the time of the 27F were solid and very advanced for the time. However, Astroza identifies "problems associated with soil classification, control of deformations, performance of reinforced concrete walls, details of confinement, and non-structural damage." In addition, an update was needed that would better calculate how much a "Chilean building" – the typical building in the country, constructed with reinforced concrete walls – moves during a major earthquake. More than 15 years after the 27F earthquake: how has the seismic standard changed in Chile with the new 2026 update? All of this incorporates the NCh433:2026 update, which "does not represent a fundamental change, but rather the consolidation and formalization of lessons learned that were gradually incorporated after the 27F earthquake." Among the highlights of the new regulations are: A more precise seismic soil classification. New requirements for complex soils. Incorporation of the predominant soil period. Clarifications for seismic hazard studies. Requirements for new materials and structural systems (especially steel and wood structures). "In the event of an earthquake similar to the 27F, this would make it possible to reduce uncertainties in the estimation of seismic demand, especially in buildings located on complex soils or near active faults," says the expert. While the Japanese model was taken into account when developing the update, the regulations are based on the country's seismic experience, seismic records, and local practices. What about buildings and houses built before the new standard? It does not necessarily mean that they are unprotected, says the dean. "The update itself recognizes that Chilean seismic engineering has historically performed very well, and that the typical Chilean building with reinforced concrete walls does not change radically with this new version of the regulations." However, older structures may be those that do not incorporate recent advances. Therefore, "the main concern today is focused on old buildings, deteriorated structures, critical infrastructure, and buildings located on particular soils." Is Chile prepared for a megathrust earthquake? "Yes. The documents highlight that Chile remains among the countries with the best seismic engineering in the world, thanks to its accumulated experience, regulatory requirements, and the historical performance of its buildings in major earthquakes," Astroza says. The new NCh433:2026 regulations consolidate the lessons learned from recent earthquakes and reduce technical uncertainties. "However, it is also recognized that current challenges go beyond preventing collapses. Today, the main concerns are urban resilience, operational continuity, critical infrastructure, non-structural damage, and rapid recovery of essential services after a major earthquake." On Wednesday, May 13th, experts will discuss the changes in requirements at the seminar "Seismic design of buildings: new process of the NCh433 standard," which will be held at the University of the Andes.