With Alaska being one of the most seismologically active regions in the world, TAPS engineers incorporated earthquake protection in the pipeline design.
The seismic design of TAPS addresses two earthquake hazards: design contingency earthquakes (DCE) and the design operating earthquakes (DOE). DCE may interrupt operations but will not compromise the integrity of pipe. DOE anticipates lower-intensity earthquake that have ground motion amplitudes half those of a DCE. Operations should be able to continue following a DCE.
Pipeline engineers designed TAPS to have greater flexibility and movement at Alaska’s major fault lines. These allowances include:
- Denali Fault: 20 feet lateral, 5 feet vertical.
- McGinnis Glacier Fault: 8 feet lateral, 6 feet vertical.
- Donnelly Dome Fault: 3 feet lateral, 10 feet vertical.
- Minor Potential Faults: 2 feet lateral, 2 feet vertical.
On Nov. 3, 2002, the pipeline withstood a magnitude 7.9 earthquake that was centered along the Denali Fault. The ground along the fault moved an estimated 18 feet horizontally and nearly 2.5 feet vertically. The quake was the largest on the Denali Fault since at least 1912 and among the strongest earthquakes recorded in North America in the last 100 years.
Due to Alyeska’s earthquake protection, the Denali Fault earthquake did not compromise the integrity of the pipeline. No oil spilled, and pipeline operations resumed after minor repairs.