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Aftershock sequence

Aftershocks after the M 6.7 44 km ESE of Ōfunato, Japan earthquake

5 aftershocks recorded inside the 63 km rupture zone, the largest M 4.4, most recently 1 week ago.

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Back to the M 6.7 44 km ESE of Ōfunato, Japan earthquake
Aftershocks5
StrongestM 4.4
Rupture zone63 km

The sequence

Newest first.

  1. 4.1Near east coast of Honshu, Japan42 km SW of the mainshock1 week ago· 50.0 km deep
  2. 4.445 km SSE of Ōfunato, Japan32 km SW of the mainshock1 week ago· 56.6 km deep
  3. 3.5Near east coast of Honshu, Japan62 km SW of the mainshock1 week ago· 60.0 km deep
  4. 3.4Near east coast of Honshu, Japan22 km NNW of the mainshock2 weeks ago· 40.0 km deep
  5. 3.5Near east coast of Honshu, Japan16 km W of the mainshock3 weeks ago· 50.0 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 63 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.

Data from USGS, EMSC and partner agencies. Magnitudes and locations are preliminary and may be revised.