explosion · reviewed by a seismologist
M 1.8ml
Earthquake near Molalla, OR
USGS: 8 km ESE of Molalla, Oregon
48 km (30 mi) SSE of Portland, OR · 41 km (25 mi) SE of Tigard, OR
- When
- 1:22 pm PST on 28 December 2017 ()
- Where
- 9 km (5 mi) ESE of Molalla, OR · earthquakes near Molalla
- Magnitude
- M 1.8 (ml)
- Depth
- -1.1 km below the surface
- Felt
- no reports yet
- Nearest
- Clackamas County, 22 km E
- Nearest mapped fault
- Mount Angel fault, 21 km from its surface trace — near is not the same as on
- Status
- Reviewed by a seismologist
USGS · last changed by USGS · we first saw it 3199 days ago
A magnitude 1.8 earthquake was recorded 9 km (5 mi) ESE of Molalla, OR, at 1:22 pm PST on 28 December 2017 (21:22 UTC). This was a minor earthquake. Quakes this small are rarely felt and do not cause damage.
Earthquakes near other towns within 30 km: Mulino, Beavercreek, Estacada, Canby, Mount Angel, Hubbard.
USGS catalogues this as explosion, not an earthquake.
How big was it?
This earthquake released about 16 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.
- Mineral, Virginia 2011 M 5.8 970,000× the energy of this one
- Magna, Utah 2020 M 5.7 680,000× the energy of this one
- Around the size people start to feel M 3.0 61× the energy of this one
- This earthquake M 1.8 about 16 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
No earthquake of M4 or more has been recorded within 50 km since our catalogue begins in 2016.
Before 2016, the USGS record lists 2 earthquakes of M5 or more within 50 km:
- 5.6 4 km E of Scotts Mills, Oregon · 15 km SW of this epicentre
- 5.0 3 km SW of Portland, Oregon · 45 km NNW 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 45.1270, -122.4717. Map © OpenStreetMap contributors.
Nearby places
| Place | Distance | Direction from the epicentre | |
|---|---|---|---|
| Clackamas County, OR | 22 km (14 mi) | E | earthquakes near Clackamas County |
| Marion County, OR | 26 km (16 mi) | SSW | earthquakes near Marion County |
| Multnomah County, OR | 47 km (29 mi) | N | earthquakes near Multnomah County |
| Yamhill County, OR | 68 km (42 mi) | WNW | earthquakes near Yamhill County |
| Washington County, OR | 68 km (42 mi) | NW | earthquakes near Washington County |
| Linn County, OR | 71 km (44 mi) | S | earthquakes near Linn County |
Places and coordinates from the US Census Bureau Gazetteer (2024). Distances are from the epicentre.
Aftershocks so far
56 earthquakes have been recorded within 50 km since this one.
- 2.2 3 km W of Mehama, Oregon
- 1.8 Washington-Oregon border region
- 1.6 7 km E of Molalla, Oregon
- 1.6 2 km E of Sherwood, Oregon
- 1.9 5 km SE of Silverton, Oregon
- 1.5 3 km SSW of Beaverton, Oregon
- 1.8 9 km ESE of Scotts Mills, OR
- 1.6 3 km NW of Mount Hood Village, Oregon
- 1.8 8 km SE of Molalla, Oregon
- 2.0 3 km W of Mehama, Oregon
- 2.4 3 km WNW of Molalla, Oregon
- 2.6 6 km ESE of Scotts Mills, Oregon
- 1.8 5 km NW of Mount Hood Village, Oregon
- 1.5 4 km W of Mulino, Oregon
- 1.7 8 km SE of Molalla, Oregon
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
- The official USGS event page — the source of record for every value above
- Did you feel it? Report it to USGS — reports go to USGS, not to us
- ShakeMap for this event, when USGS has produced one
QuakeIndex does not issue warnings. For earthquake early warning see ShakeAlert.