QuakeIndex

Fault · Idaho, Montana

Madison fault

98 kmlong (61 mi), as mapped
0.2–1 mm/yrhow fast it slips
last 150 yearssince it last broke the surface
12quakes of M2.5+ within 10 km since 2016

In plain English

The two sides move 0.2 to 1 mm a year — 2 to 10 cm every century.

It has broken the ground surface within the last 150 years.

The largest earthquake recorded near it was M 7.2 in 1959 (The 1959 Hebgen Lake, Montana Earthquake) — about 2,000,000 times the energy of an M3.0, the size people start to feel. It released about 950 kilotons of TNT.

USGS maps it as 3 sections: Madison Canyon section, northern section, southern section.

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

Centennial faultEmigrant faultRed Canyon faultHebgen fault M 7.2 · 1959 · The 1959 Hebgen Lake, Montana Earthquake M 6.1 · 1947 · 30 km SSW of Big Sky, Montana
The Madison fault as mapped at the surface (glowing), with the other mapped faults nearby, 12 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 7.2 The 1959 Hebgen Lake, Montana Earthquake
    August 18, 1959 · epicentre 18 km from the trace
  2. M 6.1 30 km SSW of Big Sky, Montana
    November 23, 1947 · epicentre 3 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 2.9 30 km W of Hebgen Lake Estates, Montana
    2026-04-05 · 7 km from the trace
  2. M 2.6 10 km W of Hebgen Lake Estates, Montana
    2026-01-10 · 9 km from the trace
  3. M 3.1 27 km W of Hebgen Lake Estates, Montana
    2025-08-13 · 5 km from the trace
  4. M 3.0 18 km NNE of Ennis, Montana
    2023-07-09 · 9 km from the trace
  5. M 3.3 17 km NNE of Ennis, Montana
    2023-01-05 · 8 km from the trace
  6. M 2.7 30 km W of Hebgen Lake Estates, Montana
    2021-07-11 · 7 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.