Reviewed by USGSNorthern Mariana Islands71y ago
M6.7 earthquake in Pagan region, Northern Mariana Islands
Wednesday, February 1, 1956, 13:41:51 UTC · 18.800°N, 145.009°E
A magnitude 6.7 earthquake struck in Pagan region, Northern Mariana Islands on Wednesday, February 1, 1956, 13:41:51 UTC, at a depth of 370.1 km (deep). It is the strongest earthquake within 300 km since an M6.7 on November 15, 1954.
- Magnitude
- 6.7
- Strong · mw
- Depth
- 370 km
- Deep
- Felt reports
- 0
- Did You Feel It?
- Est. shaking
- —
- No ShakeMap
- PAGER alert
- None
- Not issued
- Tsunami
- No flag
- USGS feed
Outlined circle: this earthquake
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
43 km
from the nearest mapped plate boundary, between the Philippine Sea and Mariana plates. Earthquakes cluster along boundaries like this one, where plates collide, pull apart or slide past each other.
Depth: deep
370 km
Deep earthquakes (over 300 km) happen deep inside subducting plates. They rarely cause damage, but can be felt faintly over very large distances.
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 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 16 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:
- 7.7Mariana Islands regionDecember 28, 1940 · 267 km E of this epicenter
- 7.2Pagan region, Northern Mariana IslandsOctober 24, 1930 · 181 km E of this epicenter
- 6.7Pagan region, Northern Mariana IslandsNovember 15, 1954 · 82 km E of this epicenter
- 6.6Alamagan region, Northern Mariana IslandsFebruary 10, 1921 · 206 km SE of this epicenter
- 6.5Pagan region, Northern Mariana IslandsOctober 28, 1930 · 173 km E of this epicenter
- 6.3Mariana Islands regionAugust 30, 1941 · 217 km E of this epicenter
- 6.3Pagan region, Northern Mariana IslandsAugust 30, 1941 · 169 km SE of this epicenter
History · NOAA
Deadliest earthquakes in this area
NOAA’s significant-earthquake database lists 1 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700. The most severe:
- 1902M8.1
Agana
22 Sep 1902 · 137 km away · intensity IX
Severe damage ($5–24M)
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.