Reviewed by USGSWashington78y ago
M6.7 earthquake 4 km WNW of Roy, Washington
Wednesday, April 13, 1949, 19:55:43 UTC · 47.014°N, 122.597°W
A magnitude 6.7 earthquake struck 4 km WNW of Roy, Washington on Wednesday, April 13, 1949, 19:55:43 UTC, at a depth of 50.0 km (shallow). USGS received 83 “Did You Feel It?” reports, with a maximum reported intensity of VIII (severe). No earthquake of this size or larger appears within 300 km in the USGS catalog since 1900.
- Magnitude
- 6.7
- Strong · mw
- Depth
- 50 km
- Shallow
- Felt reports
- 83
- Max intensity VIII
- Est. shaking
- VII
- Very strong (ShakeMap)
- PAGER alert
- None
- Not issued
- Tsunami
- No flag
- USGS feed
Outlined circle: this earthquakeColoured lines: estimated shaking intensity (USGS ShakeMap)
In context
How big was it, and why here?
Energy released
169 kilotons of TNT
That is about 11 times the Hiroshima bomb. It released about 355 times the energy of a magnitude 5.0.
Tectonic setting
252 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
50 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
Reports sent by people to USGS, grouped by place (most reports first). Intensity uses the Modified Mercalli scale (I–X): what people felt, not the magnitude.
| Place | Intensity | Reports | Distance |
|---|---|---|---|
| 98501<br>0.302 | VIII · Severe | 4 | 54 km |
| 98531<br>0.302 | VI · Strong | 4 | 64 km |
| 98589<br>0.320 | VIII · Severe | 2 | 56 km |
| 98105<br>0.320 | VII · Very strong | 2 | 90 km |
| 98168<br>0.320 | VII · Very strong | 2 | 76 km |
| 98362<br>0.320 | VI · Strong | 2 | 132 km |
| 98498<br>0.320 | VI · Strong | 2 | 52 km |
| 98332<br>0.320 | IV · Light | 2 | 63 km |
| 98368<br>0.320 | III · Weak | 2 | 118 km |
| 98336<br>0.330 | VIII · Severe | 1 | 80 km |
| 98109<br>0.330 | VII · Very strong | 1 | 86 km |
| 98366<br>0.330 | VII · Very strong | 1 | 76 km |
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 100 km
USGS has not published any M2.5+ earthquake within 100 km in the 30 days after this event.
Regional history
Past M5+ earthquakes within 300 km
USGS lists 9 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:
History · NOAA
Deadliest earthquakes in this area
NOAA’s significant-earthquake database lists 4 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700, which together caused about 8 recorded deaths. The most severe:
- 1949M7.0
Washington
13 Apr 1949 · 17 km away · intensity VIII
8 deaths$25 million damagetsunami
- 1700M9.0
Cascadia Subduction Zone
27 Jan 1700 · 291 km away
Severe damage ($5–24M)tsunami
- 1928M5.8
British Columbia
9 Feb 1928 · 284 km away
tsunami
- 1891
Puget Sound
29 Nov 1891 · 129 km away · intensity VII
tsunami
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.