QuakeIndex

Fault · Idaho, Utah

Western Bear Lake fault

58 kmlong (36 mi), as mapped
< 0.2 mm/yrhow fast it slips
< 15,000 yearssince it last broke the surface
494quakes of M2.5+ within 10 km since 2016

In plain English

The two sides move less than 0.2 mm a year — under 2 cm a century. Slow faults can still produce large earthquakes, just rarely.

Its most recent surface rupture is younger than 15,000 years.

The largest earthquake recorded near it was M 5.0 in 2017 (9 km NNW of Georgetown, Idaho) — about 1,000 times the energy of an M3.0, the size people start to feel. It released about 480 tons 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

Wasatch faultGrand Valley faultEast Cache faultEastern Bear Lake faultWest Cache faultGreys River faultRock Creek fault
The Western Bear Lake fault as mapped at the surface (glowing), with the other mapped faults nearby, 400 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 5.0 9 km NNW of Georgetown, Idaho
    September 10, 2017 · epicentre 7 km from the trace
  2. M 4.7 9 km NW of Georgetown, Idaho
    September 11, 2017 · epicentre 4 km from the trace
  3. M 4.7 12 km ESE of Soda Springs, Idaho
    September 10, 2017 · epicentre 6 km from the trace
  4. M 4.7 15 km ESE of Soda Springs, Idaho
    September 3, 2017 · epicentre 9 km from the trace
  5. M 4.7 10 km E of Soda Springs, Idaho
    September 3, 2017 · epicentre 9 km from the trace
  6. M 4.6 11 km NNW of Georgetown, Idaho
    September 6, 2017 · 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 6 km WSW of Bennington, Idaho
    2026-07-23 · 1 km from the trace
  2. M 3.0 6 km WSW of Bennington, Idaho
    2026-07-22 · 1 km from the trace
  3. M 2.9 9 km W of Bennington, Idaho
    2026-05-17 · 3 km from the trace
  4. M 3.8 8 km W of Bennington, Idaho
    2026-05-15 · 4 km from the trace
  5. M 2.7 13 km ESE of Soda Springs, Idaho
    2023-10-16 · 6 km from the trace
  6. M 2.6 13 km NNW of Georgetown, Idaho
    2022-08-08 · 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.