Historically, earthquakes occurring at these “intermediate” depths were believed to produce weaker shaking at the surface. The prevailing scientific model held that deep quakes were triggered mainly by “dehydration embrittlement.” In this process, as an oceanic plate sinks, rising temperatures and pressures release water trapped in minerals. The loss of water renders the rock weaker and more brittle, allowing cracks to form and rupture to occur. However, scientists generally believed this process ceases once temperatures exceed approximately 650 degrees Celsius. The intensity of the Calama quake suggested that a different, rarer mechanism was at work, one that significantly boosted the earthquake’s strength.
Researchers at The University of Texas at Austin, whose findings were recently published in Nature Communications, discovered that the Calama earthquake broke through hotter rock layers than expected. The study identified a rare chain reaction that accelerated the rupture, challenging long-held assumptions about the limits of deep seismic activity. “These Chilean events are causing more shaking than is normally expected from intermediate-depth earthquakes, and can be quite destructive,” said Zhe Jia, a research assistant professor at the UT Jackson School of Geosciences and the study’s lead author. “Our goal is to learn more about how these earthquakes occur, so our research could support emergency response and long-term planning.”
The discovery has significant implications for hazard assessment. If intermediate-depth earthquakes can generate stronger shaking than previously modeled, current risk maps may underestimate the potential impact on infrastructure and communities in subduction zones. The Calama event serves as a concrete example of this discrepancy: despite its depth, which typically dampens surface waves, the quake caused substantial damage. This suggests that the thermal state of the subducting slab plays a critical role in determining the energy release of deep quakes, a factor that may not be fully accounted for in traditional hazard models.
The seismic activity in this region continues to be a subject of intense monitoring. More recently, on a Monday in 2026, the United States Geological Survey (USGS) recorded a magnitude 6.9 earthquake centered in Chile’s Antofagasta region. This event struck at 7:52 p.m. local time, with an epicenter located about 16 kilometers southeast of Calama. The depth of this subsequent quake was registered at 120 kilometers, closely mirroring the depth of the 2024 event. Reports indicated that shaking was felt across a wide area, including parts of southern Peru and central Chile, with some residents describing the shaking as lasting up to a minute. Footage shared online showed objects swinging inside apartment buildings, confirming the strong perceptible impact despite the depth.
The recurrence of significant intermediate-depth quakes in the Calama-Antofagasta corridor underscores the ongoing activity in this segment of the subduction zone. While the 2024 event provided the scientific anomaly that led to the new understanding of heat-driven rupture processes, the 2026 event demonstrates that this is not an isolated incident. The consistency in depth and location suggests a persistent structural weakness or a specific thermal condition within the subducting slab that makes this region prone to powerful deep earthquakes.
For local communities, the shift in scientific understanding means that preparedness strategies may need to be revisited. If deep quakes can be as destructive as shallow ones, the focus on building codes and emergency response protocols must account for the high-frequency shaking that can be produced by events at these depths. The work of researchers like Jia is not merely academic; it is a direct input into how governments and engineers plan for the future, ensuring that infrastructure can withstand the full spectrum of seismic hazards posed by the dynamic geology of the Andes.
As monitoring continues, the interplay between temperature, rock brittleness, and water release remains a key area of study. The Calama earthquakes have forced a re-evaluation of the “ceiling” for deep seismicity, revealing that the Earth’s interior is more capable of sudden, energetic rupture than previously thought. This revised understanding is now being applied to interpret recent events, such as the 2026 magnitude 6.9 quake, providing a more nuanced and accurate picture of the seismic risks facing northern Chile and the broader region.
