Pipeline so far unscathed by North Slope's strongest earthquake ever

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ANCHORAGE, Alaska (KTUU) - Crews conducting inspections along the Trans-Alaska Pipeline have so far found no problems following Sunday’s M6.4 earthquake near Kaktovik.

Alyeska Pipeline Service Company, the firm that manages TAPS, says it has completed broad checks and aerial surveys of the pipeline and its facilities between pump stations 1 and 4, a 150-mile stretch. Starting on Tuesday, the company will begin going through everything with a fine-toothed comb.

“We’re going to go back through and check for settlements, movements, any kind of smaller issues that might have presented in the last 24 hours, or that we missed the first time around,” said Alyeska spokesperson Kate Dugan.

Michael West, who directs the Alaska Earthquake Center, said Sunday’s earthquake likely produced no more than a couple centimeters of vertical ground motion. That’s well within what the pipeline is designed to withstand.

“Each section of the pipeline might have different designed allowances depending on the seismic activity for that zone,” Dugan said. “But as we saw for this earthquake, even in a less-likely area, the pipeline operated as it was supposed to and did not have any issues.”

Anywhere that it’s above ground, the pipeline has an allowance of up to two feet of ground movement, and much more in areas near major fault lines. Near the Denali Fault Line, for example, the pipeline can handle 20 feet of lateral and 5 feet of vertical ground movement.

The Denali Fault was the site of a massive 7.9M earthquake in 2002, but even that was not enough to cause main line damage to the pipeline. TAPS was operational after only a few minor repairs.

Meanwhile, scientists and the Alaska Earthquake Center are still compiling data from the earthquake, which was the largest ever recorded on the North Slope. West says he thinks the shaker underscores the lack of data the center has for seismic activity in this part of Alaska.

“Nobody’s ever spent a lot of time trying to understand the earthquake hazards in the Eastern Brooks Range, and I think it’s very likely that we have just historically underestimated what it’s capable of,” West said.

“Now I don’t want to sound alarm bells. The North Slope is not southern Alaska, it never will be," West said. "We know very well that the Southern Coast of Alaska and up in the Interior are very seismically active, it’s not that.”

When asked if oil and gas drilling on the North Slope may have caused this earthquake, West said there was “no evidence at all” to suggest that was the case.

“If you look at the depth of this earthquake, if you look at the direction that it ruptured, it is very consistent, it’s actually what we would expect from this area,” he said. “So while this is the biggest earthquake we’ve seen by far in this area… all signs suggest that this was a perfectly natural earthquake.”



 
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