Agencies Map Tectonic Fault That Touches Southeast Alaska

August 29, 2018

Federal agencies have completed the first high-resolution mapping of a fast-moving underwater tectonic fault that extends from Vancouver Island, Canada, to southeast Alaska.

Researchers from the National Oceanic and Atmospheric Administration and the U.S. Geological Survey finished the comprehensive mapping of the 746-mile (1,200-kilometer) Queen Charlotte-Fairweather fault system, aiming to help coastal communities prepare for earthquakes and tsunamis risks with the data, the Ketchikan Daily News reported last week.

Scientists gathered an in-depth look at the sea floor from April through July along the strike-slip fault line, which is a fault that moves side to side. Using the NOAA research ship Fairweather, scientists were able to gain more insight into the fault system that lacked in-depth data, said Peter Haeussler, a research geologist with the geological survey.

The Queen Charlotte-Fairweather fault system is the counterpart to the San Andreas fault in California. The two faults create the boundary between the North America and Pacific tectonic plates.

“It’s the same plate boundary, the same two plates moving past each other – but the big difference is that the San Andreas fault is mostly on land, whereas the Queen Charlotte fault system is entirely offshore and underwater,” Haeussler said.

The Queen Charlotte fault system is one of the fastest moving strike-slip faults in the world with its slip rate of more than 2 inches (5 centimeters) per year. The San Andreas fault slips up to 1.5 inches (3.8 centimeters) per year, according to the geological survey.

Fast-moving faults more often lead to large earthquakes than slow-moving faults, Haeussler said.

Among the uses for the new data, it will be incorporated into updates for the seismic hazard map for the state, Haeussler said.

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