QuakeIndex

Fault · California

Almanor fault

40 kmlong (25 mi), as mapped
1–5 mm/yrhow fast it slips
< 130,000 yearssince it last broke the surface
104quakes 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 5.5 in 2023 (Lake Almanor Earthquake) — about 5,200 times the energy of an M3.0, the size people start to feel. It released about 2.5 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: 0–1.

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

San Andreas faultGreat Valley thrust fault systemHoney Lake faultMohawk Valley faultHat Creek faultMcArthur faultPittville faultRocky Ledge faultIndian Valley fault
The Almanor fault as mapped at the surface (glowing), with the other mapped faults nearby, 104 of the M2.5+ earthquakes within 10 km of it since 2016 (dots), . 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 5.5 Lake Almanor Earthquake
    May 11, 2023 · epicentre 3 km from the trace
  2. M 5.2 4km NW of Canyondam, CA
    May 12, 2023 · epicentre 2 km from the trace
  3. M 4.1 2km NNE of Prattville, CA
    May 26, 2023 · epicentre 2 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 3.2 2 km ESE of Prattville, CA
    2026-06-14 · 5 km from the trace
  2. M 2.5 3 km NE of Almanor, CA
    2026-02-12 · 1 km from the trace
  3. M 2.6 3 km NNE of Prattville, CA
    2025-08-12 · 1 km from the trace
  4. M 2.6 3 km ESE of Prattville, CA
    2025-03-14 · 4 km from the trace
  5. M 2.9 6 km SW of Canyondam, CA
    2025-02-12 · 5 km from the trace
  6. M 2.7 1 km E of Prattville, CA
    2025-02-01 · 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.