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Aftershock sequence

Aftershocks after the M 6.4 163 km WSW of Nikolski, Alaska earthquake

1 aftershock recorded inside the 50 km rupture zone, the largest M 3.5, most recently 1 month ago.

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Back to the M 6.4 163 km WSW of Nikolski, Alaska earthquake
Aftershocks1
StrongestM 3.5
Rupture zone50 km

The sequence

Newest first.

  1. 3.5153 km WSW of Nikolski, Alaska47 km SE of the mainshock1 month ago· 10.0 km deep

How the rupture zone is measured

An aftershock is a smaller earthquake triggered as the crust settles around the fault that ruptured. They cluster along that rupture, so the area worth searching scales with the size of the mainshock rather than being a fixed radius.

The 50 km zone above comes from the Wells & Coppersmith (1994) rupture-length relation, doubled because aftershocks routinely extend about one rupture length beyond each end of the fault, then floored at 50 km and capped at 400 km. Anything outside it is counted as separate regional seismicity, not part of this sequence.

Aftershocks are most frequent in the hours right after the mainshock and taper off over days to months. A quiet day does not mean the sequence has ended.