Some videos of the earthquake that shook the Celebes Islands on September 28, 2018, followed by a tsunami, are still trending topic. This disaster claimed two thousand lives, with an additional five thousand people missing. The destructive power of nature is undeniable, especially considering that the event “only” reached 5.1 on the moment magnitude scale (MW) (7.5 on the old Richter scale).

Can one imagine what a quake with double the magnitude would be like? It turns out such an event is not purely hypothetical—it happened not so long ago. In 1960, in the Chilean province of Valdivia, a 9.5 magnitude earthquake made history as the most powerful ever recorded with instruments.

That seismic event did not occur without warning. At six in the morning on May 21 of that year, several provinces in southern Chile (Arauco, Ñuble, but especially Concepción) were abruptly awakened by a violent tremor. This initial quake caused 125 deaths and destroyed a third of Concepción, the capital of the province with the same name. The neighboring city of Talcahuano—among other affected areas—was also largely devastated, although it would suffer an even greater disaster decades later, in 2010, due to an 8.8 MW earthquake and tsunami.

Chile Valdivia Earthquake
Seismic map of the Valdivia earthquake. The epicenter is marked with a star, in the upper part of the box. Credit: Public domain / Wikimedia Commons

The Concepción earthquake lasted just over half a minute, but it was not the end. It merely delayed what was yet to come. The next day, almost at the same time, a new earthquake struck, slightly weaker at 7.1 MW, with its epicenter in La Araucanía, whereas the previous one had been in Biobío. But as the saying goes, bad things come in threes: at 2:56 PM, a third earthquake occurred, also centered in the Araucanía region, reaching a magnitude of 7.8.

Despite the material catastrophe, the human toll was limited because people had been evacuated from their homes starting that morning. As a result, there were no more fatalities beyond those of the first day.

It seemed time to focus on organizing rescue, debris removal, and aid efforts. Or so it was believed. However, as mentioned earlier, the Concepción earthquake was merely a prologue to what was to happen very shortly thereafter—on that same day, May 22, at 3:11 PM (just a quarter of an hour later). This event impacted the previously mentioned regions as well as Los Ríos and Los Lagos.

Chile Valdivia Earthquake
Wooden houses damaged in Valdivia. Credit: Public domain / Wikimedia Commons

This earthquake was much stronger and, in fact, reached 9.5 MW (or perhaps even more, as the instruments broke at that point). To make matters worse, instead of lasting 35 seconds, it continued for 8 minutes. Seismologists now consider it to have been a sequence of 37 earthquakes triggered by a tectonic rupture in the subduction zone extending from the Arauco Peninsula to the Taitao Peninsula. The epicenters spanned approximately 1,250 kilometers parallel to the coast, affecting an area of around 400,000 square kilometers.

It is not unusual for catastrophic events to occur in that part of the world, as it lies where the Nazca Plate collides with the South American and Chiloé Plates. This causes the Nazca Plate to subduct beneath the others, generating friction that manifests as surface earthquakes and supports magma outflows through numerous volcanoes.

That said, the intensity reached in 1960 was extraordinary. Scientists estimate that such events occur only once every three centuries on average. To illustrate the magnitude, consider that tectonic plates typically move about 9 centimeters per year, but on that day, they shifted 40 meters in an instant.

Chile Valdivia Earthquake
The Canelo steamer stranded 1.5 kilometers inland. Credit: Buonasera / Wikimedia Commons

The most affected area was the city of Valdivia, the capital of the namesake province (Los Ríos Region). For this reason, the earthquake is often referred to by that name. Interestingly, most modern cement and concrete buildings collapsed, while shorter wooden structures fared better and were generally less dangerous. However, the latter were short-lived survivors, as the Calle-Calle River overflowed, flooding the streets. Then came the tsunamis.

Indeed, Valdivia is a coastal city, so it was only a matter of time before the Pacific Ocean reacted. First, there was a sudden 4-meter rise in sea level, causing damage to ships in the port, especially as the waters receded as quickly as they had risen. But ten minutes later, an 8-meter wall of water appeared on the horizon, crashing onto the land at 150 kilometers per hour and destroying everything in its path.

Hundreds of people lost their lives at that moment, but the worst was yet to come: a second, even larger wave, measuring 10 meters high. The tsunami’s magnitude caused it to impact Hawaii as well, where waves of similar height killed 61 people in the town of Hilo. The event was also felt in far-flung locations such as Japan and the islands of Oceania.

Chile Valdivia Earthquake
Expansion of the tsunami across the Pacific Ocean. Credit: Public domain / Wikimedia Commons

In Valdivia, the effects were devastating, with several Spanish fortresses from the viceregal era collapsing, along with 40% of the buildings, and the river’s mouth rendered unusable for navigation. To make matters worse, as the city was situated on fluvial sedimentation terrain and wetlands, everything turned into a colossal swamp of mud when the sea receded.

Several nearby towns disappeared from the map, with the death toll in the thousands, many more missing, and nearly 20,000 people affected (2 million nationwide). A ship was stranded a mile and a half inland, starkly demonstrating the power of the tsunami.

This was the most destructive agent, but the chaos was compounded by fires, landslides—such as the one in Pelhueco that buried an entire village along with its 300 inhabitants—and volcanic eruptions, with the Puyehue volcano erupting. Even the inland bodies of water created challenges for the population.

Chile Valdivia Earthquake
The Hawaiian town of Hilo after the tsunami. Credit: Public domain / Wikimedia Commons

Lake Villarica overflowed, and several hills collapsed onto the sluices of Lake Riñihue, blocking its drainage. The lake’s water level continued to rise, threatening catastrophic flooding if the dam were to break. For this reason, the Chilean army and several companies had to undertake a colossal project against the clock to divert part of the water while connecting the lake with neighboring ones to alleviate the situation.

Despite everything, humanity continues to challenge nature. The fact that the affected areas are located in the so-called Pacific Ring of Fire is not enough to deter occupation, and they remain populated, even though there was already a serious warning 443 years ago: in 1575, Valdivia experienced a massive earthquake whose magnitude is unknown but is estimated to have been similar to that of 1960. It also caused a tsunami (albeit moderate, with 4-meter waves) and a similar incident to that of Lake Riñihue when the Renigua lagoon overflowed and flooded the surrounding areas.

In reality, Chile has experienced hundreds of significant earthquakes from 1570 to 2015, 29 of which are considered severe (above magnitude 8). Among them are the aforementioned earthquakes of 1575 and 1960, the 1730 Valparaíso earthquake, and the 1868 Arica earthquake. As we mentioned earlier, the Ñuble tsunami occurred in 2010. And the next one…?


This article was first published on our Spanish Edition on October 13, 2018: El terremoto más fuerte de la Historia se registró en Chile en 1960


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