QuakeIndex

Fault · Alaska

Sullivan fault (Chugach-St. Elias fold and thrust belt)

34 kmlong (21 mi), as mapped
1–5 mm/yrhow fast it slips
< 130,000 yearssince it last broke the surface
9quakes of M2.5+ within 10 km since 2016

In plain English

The two sides move 1 to 5 mm a year — 10 to 50 cm (4 to 20 inches) every century.

Its most recent surface rupture is younger than 130,000 years.

The largest earthquake recorded near it was M 6.9 in 1899 (The 1899 Yakutat Bay, Alaska Earthquakes (Strong Aftershock)) — about 710,000 times the energy of an M3.0, the size people start to feel. It released about 340 kilotons 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

Denali faultPamplona faultChaix Hills fault (Chugach-St. Elias fold and thrust belt)Kosakuts fault (Chugach-St. Elias fold and thrust belt)Hope Creek fault (Chugach-St. Elias fold and thrust belt)Coal Glacier fault (Chugach-St. Elias fold and thrust belt)Malaspina fault (Chugach-St. Elias fold and thrust belt)White River syncline (Chugach-St. Elias fold and thrust belt)Yakataga anticline (Chugach-St. Elias fold and thrust belt)Miller Creek fault (Chugach-St. Elias fold and thrust belt)Yaga syncline (Chugach-St. Elias fold and thrust belt) M 6.9 · 1899 · The 1899 Yakutat Bay, Alaska Earthquakes (Strong Aftershock)
The Sullivan fault (Chugach-St. Elias fold and thrust belt) as mapped at the surface (glowing), with the other mapped faults nearby, 9 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 6.9 The 1899 Yakutat Bay, Alaska Earthquakes (Strong Aftershock)
    September 4, 1899 · epicentre 5 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 2.5 139 km WNW of Yakutat, Alaska
    2026-04-20 · 5 km from the trace
  2. M 2.5 117 km WNW of Yakutat, Alaska
    2025-12-24 · 8 km from the trace
  3. M 2.5 123 km WNW of Yakutat, Alaska
    2024-07-14 · 2 km from the trace
  4. M 2.7 122 km WNW of Yakutat, Alaska
    2024-01-05 · 4 km from the trace
  5. M 2.6 118 km WNW of Yakutat, Alaska
    2023-11-21 · 8 km from the trace
  6. M 2.8 138 km WNW of Yakutat, Alaska
    2021-08-12 · 2 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.