Earthquake Protection

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Earthquake magnitude pipeline system designed to withstand

8.5 Richter Scale (maximum). Range from 5.5 to 8.5, depending on area.

Faults crossed by pipeline

3   -  Denali
        McGinnis Glacier
        Donnelly Dome

Predicted limits of lateral movement for above ground pipeline, general

 

2 ft.

Design values for maximum movement at pipeline crossing of major faults 

Denali fault — 20 ft. lateral and 5 ft. vertical displacement

McGinnis Glacier fault — 8 ft. lateral and 6 ft. vertical displacement

Donnelly Dome fault — 3 ft. lateral and 10 ft. vertical displacement

Minor potential fault locations — 2 ft. lateral and 2 ft. vertical

Earthquake Monitoring

Alyeska's Earthquake Monitoring System (EMS) consists of sensing and processing instruments at all pump stations south of Atigun Pass and at the Valdez Terminal. A central processing unit at the Operations Control Center (OCC) is linked to the Pipeline and Terminal operator consoles. The EMS is specifically designed to process strong ground motions, to interpolate or extrapolate estimates of earth quake accelerations between the sensing instruments and to prepare a mile-by-mile report comparing the estimated accelerations along the pipeline with the pipeline seismic design criteria.

DSMAs

The instrumentation at field locations consists of accelerometers mounted on concrete pads which measure strong ground motions in three directions (tri-axial) which are connected to a Digital Strong Motion Accelerograph (DSMA). The DSMA, generally located in the Pump Station control room, processes the signals from the accelerometers in real time and reports alarms and selected data to the central processor at the OCC.

Tested

November 3, 2002 - The pipeline's earthquake design withstood a 7.9 earthquake that was centered along the Denali Fault, in the interior of Alaska, approximately 50 miles west of the pipeline. Estimates indicate that the ground along the fault moved 7 feet horizontally and nearly 2.5 feet vertically. The 7.9 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.

Last updated May 7, 2004

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