Reviewed by USGS87y ago
M7.5 earthquake in Mariana Islands region
Wednesday, January 17, 1940, 01:14:56 UTC · 17.139°N, 148.059°E
A magnitude 7.5 earthquake struck in Mariana Islands region on Wednesday, January 17, 1940, 01:14:56 UTC, at a depth of 15.0 km (shallow). No earthquake of this size or larger appears within 300 km in the USGS catalog since 1900.
- Magnitude
- 7.5
- Major · mw
- Depth
- 15 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 earthquake
In context
How big was it, and why here?
Energy released
2.7 megatons of TNT
That is about 178 times the Hiroshima bomb. It released about 5,623 times the energy of a magnitude 5.0.
Tectonic setting
22 km
from the nearest mapped plate boundary, between the Mariana and Pacific plates. Earthquakes cluster along boundaries like this one, where plates collide, pull apart or slide past each other.
Depth: shallow
15 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 200 km
USGS has not published any M2.5+ earthquake within 200 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:
- 7.2Pagan region, Northern Mariana IslandsOctober 24, 1930 · 206 km NW of this epicenter
- 6.6Alamagan region, Northern Mariana IslandsFebruary 10, 1921 · 166 km NW of this epicenter
- 6.5258 km NE of Saipan, Northern Mariana IslandsDecember 1, 1938 · 87 km W of this epicenter
- 6.5Pagan region, Northern Mariana IslandsOctober 28, 1930 · 216 km NW of this epicenter
- 6.3215 km ENE of Saipan, Northern Mariana IslandsMarch 19, 1932 · 129 km SW of this epicenter
- 6.0Pagan region, Northern Mariana IslandsDecember 25, 1934 · 211 km NW of this epicenter
- 5.9227 km NNE of Saipan, Northern Mariana IslandsNovember 12, 1936 · 126 km W 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 · 238 km away · intensity IX
Severe damage ($5–24M)
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.