Earthquake · reviewed by a seismologist
M 4.7mw
Southern Alaska
Yes. A magnitude 4.7 earthquake was recorded in Southern Alaska at 05:35 UTC on 2017-10-19, 102 km deep. 205 people have reported feeling it to USGS.
- When
- Magnitude
- M 4.7 (mw)
- Depth
- 102 km below the surface
- Felt
- 205 reports · strongest reported intensity IV
- Measured shaking
- intensity III (ShakeMap)
- USGS impact alert
- green
- Tsunami
- USGS flagged this event for tsunami evaluation. Follow tsunami.gov for official messages.
- Nearest
- Kenai Peninsula Borough, 82 km NNE
- Status
- Reviewed by a seismologist
USGS · last changed by USGS · we first saw it 1191 days ago
This was a light earthquake. It is usually felt clearly nearby and can rattle windows and dishes, but damage is uncommon.
At this magnitude and depth, people at rest would likely notice it out to about 123 km (76 mi) from the epicentre. 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 170 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 5.7 would have released about 32 times as much.
- Northridge, California 1994 M 6.7 1,000× the energy of this one
- Mineral, Virginia 2011 M 5.8 45× the energy of this one
- Magna, Utah 2020 M 5.7 32× the energy of this one
- This earthquake M 4.7 about 170 tons of TNT
- Around the size people start to feel M 3.0 this one released 350× more
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 7.1 on 2016-01-24 — about 4,000 times the energy of this one.
Before 2016, the USGS record lists 21 earthquakes of M5 or more within 50 km; the five largest:
- 6.4 52 km ENE of Pedro Bay, Alaska · 17 km NNW of this epicentre
- 6.2 70 km E of Port Alsworth, Alaska · 45 km N of this epicentre
- 6.0 53 km W of Anchor Point, Alaska · 21 km ENE of this epicentre
- 5.9 66 km ENE of Pedro Bay, Alaska · 32 km N of this epicentre
- 5.9 Southern Alaska · 38 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 59.7445, -153.1315. Map © OpenStreetMap contributors.
Nearby places
| Place | Distance | Direction from the epicentre | |
|---|---|---|---|
| Kenai Peninsula Borough, AK | 82 km (51 mi) | NNE | earthquakes near Kenai Peninsula Borough |
Places and coordinates from the US Census Bureau Gazetteer (2024). Distances are from the epicentre.
Aftershocks so far
57 earthquakes have been recorded within 50 km since this one.
- 2.2 51 km SE of Pedro Bay, Alaska
- 1.9 38 km ESE of Pedro Bay, Alaska
- 2.2 41 km ENE of Pedro Bay, Alaska
- 1.8 56 km ENE of Pedro Bay, Alaska
- 1.6 40 km ESE of Pedro Bay, Alaska
- 1.8 61 km WNW of Nanwalek, Alaska
- 1.6 63 km ESE of Pedro Bay, Alaska
- 1.6 52 km ESE of Pedro Bay, Alaska
- 1.5 61 km ESE of Pedro Bay, Alaska
- 1.9 49 km WNW of Nanwalek, Alaska
- 1.6 46 km W of Anchor Point, Alaska
- 1.9 62 km ESE of Pedro Bay, Alaska
- 2.0 39 km ENE of Pedro Bay, Alaska
- 1.6 60 km W of Happy Valley, Alaska
- 3.4 38 km SE of Pedro Bay, Alaska
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.