Proposed Dams Near Seismic Fault

Residents and activists already concerned about the devastating impact proposed dam projects could have on southern Chile’s pristine wilderness, now have a new argument for why it is simply a bad idea to dam Patagonia’s rivers: earthquakes.

In recent weeks, the towns of Pueto Aysén and Puerto Chacabuco in southern Chile’s Region XI have been jolted by an unusual spate of seismic activity that continues to rock the area. In the last week of January alone, seismologists recorded an astounding 1,700 tremors—only a small but still alarming number of which were noticeable. A few of the small quakes registered as high as 6 on the Mercalli scale. Locals initially feared a repeat of the devastating 1991 eruption of the nearby Hudson Volcano, which was preceded by a similar cluster of tremors and quakes.

Authorities, however, have since come up with another theory to explain the tremors. A team of scientists dispatched to the area in late January concluded that the quakes are likely being caused by underground magma flow in the nearby Aysén fjord. According to the experts, the magma, which is pressuring a subterranean tectonic plate, could eventually push its way to the surface and form a relatively small volcanic cone on the seafloor of the fjord.

The scientific team—made up of a Universidad de Chile seismologist, a geologist from the National Mining and Geologic Service and a volcanologist from the National Emergency Office—identified the epicenter of the tremors as being approximately 12 miles northwest of Puerto Chacabuco.

Xstrata’s project map superimposed on map of region with the epicenter of the quake at left. (Courtesy: http://www.eldivisadero.cl)
That, say some area residents, is dangerously close to the site of a 600-megawatt hydroelectric dam the Swiss mining company Xstrata—working through its local affiliate Energía Austral—plans to build on the Cuervo River. Xstrata, which has already submitted the requisite Environmental Impact Study, is looking to begin construction on the $600 million project sometime next year.

During a community forum organized earlier this month by journalist Patricio Segura and architect Peter Hartmann, participants expressed major concern about the Xstrata project’s proximity to the estimated epicenter of the quakes.

“It seems dangerous to me,” said Paola Bustamante, a teacher from Puerto Aysén. “It’s terrifying to me to think about earthquakes plus dams. With the appearance of this new variable, I think we need to take an even deeper look (at this proposal) and tell people the truth, not hide anything.”

“The people are really worried about the issue of quakes,” said Hartmann, who also heads the regional office of an environmental group called the Committee for the Defense of Flora and Fauna (CODEFF). “The problem is that the epicenter of the recent quakes and the volcano that might form there are exactly in front of the place where they want to build the dam. This represents a risk even for the company.”

Here is the full article.