Unearthing the Seismic Footprint of the 1973 Chilean Coup through Historical Seismograms

In a remarkable intersection of history and science, fragile seismograms have become a window into the seismic consequences of the 1973 Chilean coup d'état. As military vehicles rumbled toward Santiago's presidential palace, and bombs dropped from the Chilean Air Force echoed through the city, one lone seismometer captured these harrowing events in real time.

In a recent study published in Seismological Research Letters, Sergio León-Rios of Universidad de Chile and his colleagues delve into the compelling data preserved on these historical seismograms. They advocate for the preservation and study of such records, not just for their scientific value but for their cultural significance as well.

Initiated in 2023, the analysis coincided with the 50th anniversary of the coup, prompting a wave of reflection and commemorative events across the country. León-Rios stated, “Finding these records provided us with a unique perspective to describe what transpired during the coup’s tumultuous days.”

This research is part of a broader initiative known as Herencia Sísmica, which unites scientists and artists to highlight the historical significance of Chile's geological disasters. The seismograms in question were recorded by a single electromagnetic device positioned just 2 kilometers from La Moneda, the site of President Salvador Allende's fateful final stand.

In a striking observation, the researchers noted an abrupt decrease in ambient seismic noise on September 11, 1973. The city's routine was irrevocably altered as a military curfew was announced, echoing through the silent streets of Santiago. The seismometer later captured the thunderous sounds of Chilean fighter jets as they bombarded La Moneda, as well as the rumble of heavy vehicles mobilizing from a nearby military base.

The data paints a vivid picture: before the coup, the city vibrated with typical urban sounds; after the curfew was imposed, it fell into an almost eerie silence. León-Rios remarked on this stark transition, noting, “Seeing how the city shifted from regular seismic noise to nearly complete silence due to the curfew left a profound impression.”

Remarkably, even in this hush, the seismometer detected three minor earthquakes, indicative of Chile's constantly shifting tectonic plates.

The seismogram records themselves were stored in a warehouse at Universidad de Chile, where they narrowly escaped destruction during a fire in 1985. Thanks to the quick actions of Diana Comte, a geophysics professor, many of these crucial historical records were preserved from the flames.

The authors emphasize the importance of recognizing Chile’s extensive history with natural disasters as a fundamental aspect of its cultural heritage. By collaborating with the Centro de Investigación para la Gestión Integrada de Riesgo de Desastres, León-Rios’ team aims to ensure that not only the physical records are preserved but also the stories and data that accompany them.

Their efforts extend to a planned art exhibition in January 2025, showcasing both the historic seismograms and new art inspired by these records. “Chileans possess a unique social understanding of earthquakes,” León-Rios explained, highlighting how many can intuitively assess the severity of tremors they've experienced. “However, more work is needed to elevate the importance of these records in our society.”

The initiative aims for robust funding to maintain these invaluable records and make them accessible for future generations. The ultimate goal is to encourage public dialogue about earthquakes, enhancing community preparedness for future seismic events.

This melding of history, culture, and science serves as a potent reminder of the profound impact of the past on Chile's present and future. As these stories unfold through seismic data, they empower the nation to reflect, learn, and grow.