QuakeIndex

Earthquake · reviewed by a seismologist

M 1.7ml

Earthquake near Helena Valley West Central, MT

No earthquake was likely felt in Helena Valley West Central in the 24 hours to 8:21 pm MST (03:21 UTC). The last one was M 1.5, 4 km (2 mi) SE, at 3:20 pm MDT on 18 May 2025, estimated intensity II (weak) in town. Every earthquake near Helena Valley West Central

This page: a magnitude 1.7 earthquake was recorded 45 km (28 mi) north-northeast of Helena Valley West Central, MT, at 1:18 am MST on 2 January 2017 (08:18 UTC), 9.7 km deep.

USGS: 5 km ESE of Craig, Montana

1:18 am MST, Jan 2, 2017 · · 9.7 km deep · released about 9.6 lb of TNT

Every earthquake near Helena Valley West Central Felt it? Tell USGS Check my area
10 km30 km60 km120 km N Lewis and Clark County 38 kmCascade County 51 kmPowell County 82 kmBroadwater County 86 kmMeagher County 90 kmTeton County 90 kmJefferson County 104 km
Distance rings around the epicentre, with the nearest towns at their true direction and later quakes as coloured dots. Not a shaking map — see the USGS ShakeMap for that.
When
1:18 am MST on 2 January 2017 ()
Where
45 km (28 mi) north-northeast of Helena Valley West Central, MT · earthquakes near Helena Valley West Central
Montana today
every earthquake in Montana in the last 24 hours
Magnitude
M 1.7 (ml)
Depth
9.7 km below the surface
Felt
no reports yet
Nearest
Lewis and Clark County, 38 km WNW
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 3599 days ago

This was a minor earthquake. Quakes this small are rarely felt and do not cause damage.

At this magnitude and depth, people at rest would likely notice it out to about 7 km (4 mi) from the epicentre. In Helena Valley West Central, 45 km away, the estimate is intensity I (not felt). Estimated from magnitude, depth and distance with the intensity equation USGS Did You Feel It? uses; felt reports, where there are any, are the measurement.

How big was it?

This earthquake released about 9.6 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 2.7 would have released about 32 times as much.

  1. Mineral, Virginia 2011 M 5.8 1,600,000× the energy of this one
  2. Magna, Utah 2020 M 5.7 1,100,000× the energy of this one
  3. Around the size people start to feel M 3.0 99× the energy of this one
  4. This earthquake M 1.7 about 9.6 lb of TNT

Energy from the Gutenberg–Richter relation (log10E = 1.5M + 4.8), rounded to two figures; bar length is magnitude, which is already a logarithm of energy. Magnitudes of past earthquakes from the USGS catalogue.

For this area

The largest earthquake within 50 km since 2016 was M 4.3 on 2016-01-30 — about 9,800 times the energy of this one.

Before 2016, the USGS record since 1900 lists no earthquake of M5 or more within 50 km.

Since 2016: the QuakeIndex catalogue (US, M1.5+), built from the USGS FDSN event service. Before 2016: USGS ComCat, M5+ from 1900. Distances are between epicentres. This is the record, not a forecast.

Where

Epicentre 47.0505, -111.8938. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection from the epicentre
Lewis and Clark County, MT 38 km (24 mi) WNW earthquakes near Lewis and Clark County
Cascade County, MT 51 km (31 mi) NE earthquakes near Cascade County
Powell County, MT 82 km (51 mi) WSW earthquakes near Powell County
Broadwater County, MT 86 km (53 mi) SSE earthquakes near Broadwater County
Meagher County, MT 90 km (56 mi) SE earthquakes near Meagher County
Teton County, MT 90 km (56 mi) NNW earthquakes near Teton County

Places and coordinates from the US Census Bureau Gazetteer (2024). Distances are from the epicentre.

Aftershocks so far

55 earthquakes have been recorded within 50 km since this one.

  1. 3.1 13 km NNW of Marysville, Montana
  2. 2.4 4 km NNW of Helena Valley Northeast, Montana
  3. 2.3 13 km WSW of Craig, Montana
  4. 1.6 9 km SSE of Craig, Montana
  5. 2.1 6 km NE of Helena Valley Northeast, Montana
  6. 2.3 14 km NNE of Helena Valley Northwest, Montana
  7. 3.3 4 km NNE of Marysville, Montana
  8. 1.6 Western Montana
  9. 1.5 16 km SSE of Craig, Montana
  10. 1.6 16 km S of Craig, Montana
  11. 2.3 Western Montana
  12. 1.5 14 km SSW of Craig, Montana
  13. 1.8 14 km NNE of Marysville, Montana
  14. 1.6 29 km SE of Craig, Montana
  15. 2.3 18 km E of Lincoln, Montana

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of . QuakeIndex does not forecast aftershocks. When USGS issues an operational aftershock forecast it appears on the USGS event page.

On USGS

QuakeIndex does not issue warnings. For earthquake early warning see ShakeAlert.