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Aftershock sequence

Aftershocks after the M 6.7 12 km SE of Santiago, Philippines earthquake

8 aftershocks recorded inside the 63 km rupture zone, the largest M 4.3, most recently 3 days ago.

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Back to the M 6.7 12 km SE of Santiago, Philippines earthquake
Aftershocks8
StrongestM 4.3
Rupture zone63 km

The sequence

Newest first.

  1. 3.1Philippine islands region47 km E of the mainshock3 days ago· 5.0 km deep
  2. 3.1Mindanao, Philippines29 km ENE of the mainshock1 week ago· 9.0 km deep
  3. 3.0Mindanao, Philippines30 km E of the mainshock1 week ago· 7.0 km deep
  4. 4.3Mindanao, Philippines51 km N of the mainshock2 weeks ago· 21.0 km deep
  5. 3.9Philippine islands region45 km E of the mainshock2 weeks ago· 10.0 km deep
  6. 3.0Mindanao, Philippines46 km N of the mainshock3 weeks ago· 23.0 km deep
  7. 4.1Mindanao, Philippines32 km NNE of the mainshock3 weeks ago· 19.0 km deep
  8. 3.1Mindanao, Philippines19 km NNE of the mainshock4 weeks ago· 26.0 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.