Reviewed by USGSWashington46y ago
M3.1 earthquake 33 km NE of Amboy, Washington
Sunday, July 20, 1980, 17:42:09 UTC · 46.101°N, 122.120°W
A magnitude 3.1 earthquake struck 33 km NE of Amboy, Washington on Sunday, July 20, 1980, 17:42:09 UTC, at a depth of 3.3 km (shallow).
- Magnitude
- 3.1
- Minor · md
- Depth
- 3 km
- Shallow
- Felt reports
- 0
- Did You Feel It?
- Est. shaking
- —
- No ShakeMap
- PAGER alert
- None
- Not issued
- Tsunami
- No flag
- USGS feed
Outlined circle: this earthquakeDashed circle: 50 km aftershock search area
In context
How big was it, and why here?
Energy released
674 kg of TNT
That is about 1/22,353 of the Hiroshima bomb. A magnitude 5.0 releases about 708 times more energy.
Tectonic setting
271 km
from the nearest mapped plate boundary, between the Juan de Fuca and North American plates. Earthquakes this far from a boundary happen on faults inside a plate, often less frequently but sometimes strongly.
Depth: shallow
3 km
Shallow earthquakes (under 70 km) produce the strongest surface shaking for their size, so they are the ones most likely to cause damage near the epicenter.
Did You Feel It?
Where it was felt
No “Did You Feel It?” reports have been published for this event yet. If you felt it, you can add your report on the USGS website.
I felt it — report to USGS ↗USGS PAGER estimate
Who was exposed to shaking
USGS publishes PAGER impact estimates for significant earthquakes, usually within an hour. No PAGER estimate is available for this event.
After the main event
Aftershocks within 50 km
USGS lists 3 M2.5+ earthquakes within 50 km in the following 30 days; the largest was M2.7 on July 23, 1980. Most nearby activity right after a large earthquake is aftershocks, which usually become less frequent over days and weeks.
Regional history
Past M5+ earthquakes within 300 km
USGS lists 30 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:
- 6.74 km WNW of Roy, WashingtonApril 13, 1949 · 108 km N of this epicenter
- 6.71 km ENE of Dash Point, WashingtonApril 29, 1965 · 138 km N of this epicenter
- 6.1Puget Sound region, WashingtonNovember 13, 1939 · 153 km N of this epicenter
- 6.03 km SW of Garrett, WashingtonJuly 16, 1936 · 285 km E of this epicenter
- 5.8Puget Sound area, WashingtonFebruary 15, 1946 · 144 km NW of this epicenter
- 5.738 km NNE of Amboy, WashingtonMay 18, 1980 · 13 km NW of this epicenter
History · NOAA
Deadliest earthquakes in this area
NOAA’s significant-earthquake database lists 5 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700, which together caused about 76 recorded deaths. The most severe:
- 1980M5.2
Mt St Helens
18 May 1980 · 14 km away · intensity V
61 deaths$2.0 billion damagetsunami
- 1949M7.0
Washington
13 Apr 1949 · 124 km away · intensity VIII
8 deaths$25 million damagetsunami
- 1965M6.6
Seattle
29 Apr 1965 · 145 km away · intensity VIII
7 deaths$28 million damage
- 1700M9.0
Cascadia Subduction Zone
27 Jan 1700 · 256 km away
Severe damage ($5–24M)tsunami
- 1891
Puget Sound
29 Nov 1891 · 236 km away · intensity VII
tsunami
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.