QuakeIndex

Fault · California

Mad River fault

81 kmlong (50 mi), as mapped
> 5 mm/yrhow fast it slips
< 15,000 yearssince it last broke the surface
33quakes 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 6.5 in 1932 (The 1932 Eureka, California Earthquake) — about 150,000 times the energy of an M3.0, the size people start to feel. It released about 71 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

San Andreas faultBartlett Springs fault systemLittle Salmon faultBald Mountain-Big Lagoon faultMattole Canyon fault M 6.5 · 1932 · The 1932 Eureka, California Earthquake M 6.4 · 1954 · The 1954 Eureka-Arcata, California Earthquake
The Mad River fault as mapped at the surface (glowing), with the other mapped faults nearby, 33 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 6.5 The 1932 Eureka, California Earthquake
    June 6, 1932 · epicentre 23 km from the trace
  2. M 6.4 The 1954 Eureka-Arcata, California Earthquake
    December 21, 1954 · epicentre 1 km from the trace
  3. M 4.8 19km SSE of Blue Lake, CA
    July 21, 2016 · epicentre 4 km from the trace
  4. M 4.4 13km ESE of Blue Lake, CA
    February 6, 2019 · epicentre 5 km from the trace
  5. M 4.0 9 km SE of Blue Lake, CA
    May 15, 2024 · epicentre on 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 3.0 16 km ENE of Hydesville, CA
    2026-03-21 · 8 km from the trace
  2. M 3.2 4 km NNE of Blue Lake, CA
    2025-12-11 · 2 km from the trace
  3. M 2.9 14 km SE of Pine Hills, CA
    2025-08-01 · 5 km from the trace
  4. M 3.1 4 km WSW of Arcata, CA
    2025-06-22 · 5 km from the trace
  5. M 4.0 9 km SE of Blue Lake, CA
    2024-05-15 · 0 km from the trace
  6. M 2.9 4 km SW of Westhaven-Moonstone, CA
    2023-10-04 · 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.