Small intermediate-depth earthquakes cluster in a volume about 20 km in diameter beneath Gold King, a landing strip on the northern flanks of the Alaska Range. These events, almost 600 km from the Aleutian trench, are the northern-most which can be identified as being associated with the Benioff zone extending inland from Cook Inlet west of Anchorage. First-motion observations of the Gold King events at local stations can be combined to determine a tensional axis dipping steeply to the north at an azimuth just west of north. This composite mechanism suggests that the slab is subjected to down-dip tensional forces, probably as a result of gravitational sinking.

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