We had a stark reminder today of just how vulnerable BHP Billiton is to events beyond its control, like earthquakes. When news of a quake in Chile was received in the Melbourne and London offices of the world’s biggest miner, it would have sent a chill through those pushing the huge Rio Tinto merger deal.

The 7.7 magnitude earthquake rattled the copper producing areas of northern Chile, shutting nine mines, including BHP’s Escondida.

World prices surged sharply on the news with December copper futures jumping 18.95 US cents, or more than 6%, to close at $US3.2965 a pound on the Comex division of the New York Mercantile Exchange. It was one of the largest one day rises ever — ending the metal’s biggest losing streak for months, which has been driven by slowing demand in China and the US and rising stockpiles.

Gold prices in New York were rising before news of the quake became known, and they rose more sharply afterwards, ending up $US15.70 an ounce at $US814.70 an ounce.

The quake was centered 170 kilometers north-northeast of the port city of Antofagasta in northern Chile, the US Geological Survey said. Mines including Escondida, the world’s largest copper mine, and Codelco’s big Chuquicamata mine lost power.

So if you’re a local investor and you’ve seen the surge in the copper price, do you buy BHP because of the rebound in a key commodity or sell because the Escondida mine could be damaged?