QuakeIndex

Fault · California

Bald Mountain-Big Lagoon fault

56 kmlong (35 mi), as mapped
1–5 mm/yrhow fast it slips
< 130,000 yearssince it last broke the surface
24quakes 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 6.4 in 1954 (The 1954 Eureka-Arcata, California Earthquake) — about 130,000 times the energy of an M3.0, the size people start to feel. It released about 60 kilotons of TNT.

This week vs. its last ten years

Too quiet to rank: fewer than half a year's worth of weeks with any M1.5+ quake within 5 km, in ten years. A single quake here would read as "unusual", so we do not score it.

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

Little Salmon faultMad River fault M 6.4 · 1954 · The 1954 Eureka-Arcata, California Earthquake
The Bald Mountain-Big Lagoon fault as mapped at the surface (glowing), with the other mapped faults nearby, 24 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 6.4 The 1954 Eureka-Arcata, California Earthquake
    December 21, 1954 · epicentre 4 km from the trace
  2. M 4.8 19km SSE of Blue Lake, CA
    July 21, 2016 · epicentre 7 km from the trace
  3. M 4.4 13km ESE of Blue Lake, CA
    February 6, 2019 · epicentre on the trace
  4. M 4.3 16km WSW of Weitchpec, CA
    January 20, 2023 · epicentre 9 km from the trace
  5. M 4.0 9 km SE of Blue Lake, CA
    May 15, 2024 · 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 3.2 4 km NNE of Blue Lake, CA
    2025-12-11 · 7 km from the trace
  2. M 4.0 9 km SE of Blue Lake, CA
    2024-05-15 · 5 km from the trace
  3. M 2.6 13 km NNW of Trinidad, CA
    2023-10-05 · 8 km from the trace
  4. M 2.9 4 km SW of Westhaven-Moonstone, CA
    2023-10-04 · 7 km from the trace
  5. M 4.3 16km WSW of Weitchpec, CA
    2023-01-20 · 9 km from the trace
  6. M 3.7 16km WSW of Weitchpec, CA
    2023-01-19 · 9 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.