QuakeIndex

Fault · Alaska

Transition fault

376 kmlong (234 mi), as mapped
> 5 mm/yrhow fast it slips
< 15,000 yearssince it last broke the surface
20quakes of M2.5+ within 10 km since 2016

In plain English

The two sides grind past each other faster than 5 mm a year — more than half a metre (20 inches) every century.

Its most recent surface rupture is younger than 15,000 years.

The largest earthquake recorded near it was M 8.2 in 1899 (The 1899 Yakutat Bay, Alaska Earthquakes (First Major Event)) — about 55,000,000 times the energy of an M3.0, the size people start to feel. It released about 26 megatons of TNT.

This week vs. its last ten years

0/100

quiet

0 quakes of M1.5+ within 5 km of the trace in the last 7 days — busier than 0% of weeks since 2016. A normal week: 0–0.

Computed from the USGS catalogue · a description of the past, not a forecast · method

Alaska-Aleutian subduction zoneDenali faultFairweather fault systemPamplona faultGulf of Alaska shear zoneYakutat fault (also known as Foothills fault)Boundary faultTen Fathom faultKayak faultBancas Point faultOtmeloi fault M 8.2 · 1899 · The 1899 Yakutat Bay, Alaska Earthquakes (First Major Event) M 7.0 · 1899 · The 1899 Yakutat Bay, Alaska Earthquakes (Strong Aftershock)
The Transition fault as mapped at the surface (glowing), with the other mapped faults nearby, 20 of the M2.5+ earthquakes within 10 km of it since 2016 (dots), and the epicentres of the large historic earthquakes recorded near it (rings). Traces: USGS Quaternary Fault and Fold Database. Historic epicentres are estimates.

Every year since 2016

Earthquakes of M2.5+ with an epicentre within 10 km of the mapped trace. Near is not the same as on: some will have slipped on neighbouring faults.

The big ones recorded near it

  1. M 8.2 The 1899 Yakutat Bay, Alaska Earthquakes (First Major Event)
    September 4, 1899 · epicentre 23 km from the trace
  2. M 7.0 The 1899 Yakutat Bay, Alaska Earthquakes (Strong Aftershock)
    September 23, 1899 · epicentre 21 km from the trace
  3. M 4.0 152 km WSW of Elfin Cove, Alaska
    September 7, 2026 · epicentre 4 km from the trace

Before 1973 from the USGS ComCat historical catalogue (within 25 km; epicentres of old earthquakes are estimates). Since 2016, M4+ within 10 km.

Most recent near it

  1. M 2.8 114 km WSW of Elfin Cove, Alaska
    2026-09-17 · 8 km from the trace
  2. M 4.0 152 km WSW of Elfin Cove, Alaska
    2026-09-07 · 4 km from the trace
  3. M 3.3 158 km WSW of Elfin Cove, Alaska
    2026-09-07 · 6 km from the trace
  4. M 2.8 132 km SW of Yakutat, Alaska
    2026-08-13 · 1 km from the trace
  5. M 2.9 154 km WSW of Elfin Cove, Alaska
    2026-01-28 · 3 km from the trace
  6. M 2.7 159 km WSW of Elfin Cove, Alaska
    2026-01-24 · 4 km from the trace

Neighbouring faults

Fault trace, slip rate and age: USGS Quaternary Fault and Fold Database (public domain), simplified for the web. Earthquakes: USGS ComCat. QuakeIndex does not forecast earthquakes; a fault's history describes the past. For early warning use ShakeAlert.