QuakeIndex

Earthquake · reviewed by a seismologist

M 1.8ml

Earthquake near Helena, MT

No earthquake was likely felt in Helena in the 24 hours to 1:40 pm MST (20:40 UTC). The last one was M 1.6, 7 km (4 mi) SE, at 11:34 am MDT on 14 October 2026, estimated intensity II (weak) in town. Every earthquake near Helena

This page: a magnitude 1.8 earthquake was recorded 35 km (21 mi) north-northwest of Helena, MT, at 10:24 am MDT on 6 July 2019 (16:24 UTC), 1.7 km deep.

USGS: 14 km NNE of Marysville, Montana

10:24 am MDT, Jul 6, 2019 · · 1.7 km deep · released about 15 lb of TNT

Every earthquake near Helena Felt it? Tell USGS Check my area
10 km30 km60 km120 km N Lewis and Clark County 30 kmPowell County 53 kmBroadwater County 82 kmCascade County 83 kmJefferson County 84 kmMeagher County 105 kmTeton County 105 kmGranite County 106 kmDeer Lodge County 111 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
10:24 am MDT on 6 July 2019 ()
Where
35 km (21 mi) north-northwest of Helena, MT · earthquakes near Helena
Montana today
every earthquake in Montana in the last 24 hours
Magnitude
M 1.8 (ml)
Depth
1.7 km below the surface
Felt
no reports yet
Nearest
Lewis and Clark County, 30 km NNW
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 2685 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 13 km (8 mi) from the epicentre. In Helena, 35 km away, the estimate is intensity II (weak). 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.

Earthquakes near other towns within 30 km: Helena Valley Northwest, Helena Valley West Central, Helena Valley Northeast.

How big was it?

This earthquake released about 15 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 2.8 would have released about 32 times as much.

  1. Mineral, Virginia 2011 M 5.8 1,000,000× the energy of this one
  2. Magna, Utah 2020 M 5.7 730,000× the energy of this one
  3. Around the size people start to feel M 3.0 65× the energy of this one
  4. This earthquake M 1.8 about 15 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 5.8 on 2017-07-06 — about 1,000,000 times the energy of this one.

Before 2016, the USGS record lists 3 earthquakes of M5 or more within 50 km:

  1. 5.9 2 km ENE of Helena, Montana · 35 km SSE of this epicentre
  2. 5.9 The 1935 Helena, Montana Earthquakes (Largest Aftershock) · 47 km SE of this epicentre
  3. 5.0 2 km ENE of Helena, Montana · 35 km SSE of this epicentre

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 46.8735, -112.2288. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection from the epicentre
Lewis and Clark County, MT 30 km (19 mi) NNW earthquakes near Lewis and Clark County
Powell County, MT 53 km (33 mi) W earthquakes near Powell County
Broadwater County, MT 82 km (51 mi) SE earthquakes near Broadwater County
Cascade County, MT 83 km (51 mi) NE earthquakes near Cascade County
Jefferson County, MT 84 km (52 mi) S earthquakes near Jefferson County
Meagher County, MT 105 km (65 mi) ESE earthquakes near Meagher County

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

Aftershocks so far

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

  1. 1.6 Western Montana
  2. 1.5 16 km SSE of Craig, Montana
  3. 1.5 16 km SE of Lincoln, Montana
  4. 1.7 16 km ESE of Lincoln, Montana
  5. 2.0 14 km ESE of Lincoln, Montana
  6. 2.0 5 km SSW of Avon, Montana
  7. 1.5 14 km SE of Lincoln, Montana
  8. 1.5 14 km ESE of Lincoln, Montana
  9. 1.8 16 km NW of Marysville, Montana
  10. 3.2 8 km S of Lincoln, Montana
  11. 1.5 4 km WSW of Lincoln, Montana
  12. 1.5 12 km ESE of Lincoln, Montana
  13. 1.6 16 km S of Craig, Montana
  14. 2.3 13 km ESE of Lincoln, Montana
  15. 1.5 15 km SE 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.