Codelco Halts El Teniente Expansion After Finding New Seismic Risk, One Year After Collapse Killed Six

Codelco, Chile's state-owned copper giant, has halted expansion work at part of its El Teniente mine after new studies found seismic risks nobody had flagged before.

The company said it's pausing development in the Andes Norte section specifically, to ensure worker safety. That's not the exact spot where six workers died a year ago, but it sits near the Andesita and Teniente 7 sections that were most affected by that collapse.

What Codelco Found

According to MINING.COM, Codelco says analyses over the past six months point to seismic risks related to the depth of the Andes Norte deposit, different from those that had been previously identified and monitored. The company's own statement says these analyses "have identified the existence of an emerging seismic phenomenon with characteristics different from the risks that have historically been known and managed in the operation."

El Teniente is more than a century old, and Codelco's own account suggests the ground still holds risks the company hadn't fully mapped.

Codelco says "the available evidence is consistent with the possible existence" of this emerging risk, tied to the greater depth of the Andes Norte project. That's careful, lawyered language. The company isn't saying the risk is confirmed. It's saying it's plausible enough to pause and study further before pushing deeper.

The Collapse That Started This

On July 31, 2025, a collapse at El Teniente killed six workers. The impact was equivalent to a 4.2-magnitude earthquake, according to MINING.COM. That's not a cave-in from a bad support beam. That's the mountain itself moving.

The collapse hit the Andesita and Teniente 7 sections. Codelco shut down production across multiple parts of the mine in the aftermath. A year later, the company is still investigating the precise cause. Codelco faces criminal, regulatory, and technical investigations, and none have publicly concluded as of this writing.

Why This Matters Beyond Chile

El Teniente isn't some small operation. It's the biggest underground copper mine on the planet, spanning more than 4,500 kilometers of tunnels and underground galleries in the Andes, about 75 kilometers southeast of Santiago. It's been running for more than a century.

Codelco was grappling with lifting copper production out of a quarter-century low even before this pause. MINING.COM notes that mining companies worldwide are increasingly turning to very deep underground operations to boost output, in some cases compensating for aging, depleted mines. That's the trend across the industry, not just at El Teniente. Deeper mining apparently comes with seismic risks that, according to Codelco's own admission, current monitoring systems weren't built to catch.

If the world's biggest underground copper mine can't safely go deeper without hitting seismic surprises, that's a constraint worth watching for anyone tracking global copper supply.

The Company's Response

Codelco isn't hiding this. It put out a public statement acknowledging the emerging risk rather than treating the 2025 collapse as a disconnected, one-off accident. The company is saying the depth itself may be part of the problem, and it's pausing expansion in Andes Norte rather than pushing through it.

A state-run miner facing pressure to boost production chose to halt a project over safety data rather than gamble on it. Whether that caution came too late for the six men who died in 2025 is a separate, harder question, and one still being investigated by Chilean authorities.

What happens next is unclear. Codelco says it will continue to study the Andes Norte risk. No timeline has been given for when, or whether, expansion resumes. The criminal, regulatory, and technical investigations into the 2025 collapse also remain open, with no findings released as of this writing.