Reviewed by USGSNorthern Mariana Islands37y ago
M6.3 earthquake 197 km E of Saipan, Northern Mariana Islands
Friday, April 6, 1990, 14:57:20 UTC · 15.177°N, 147.596°E
A magnitude 6.3 earthquake struck 197 km E of Saipan, Northern Mariana Islands on Friday, April 6, 1990, 14:57:20 UTC, at a depth of 15.5 km (shallow). It is the strongest earthquake within 300 km since an M7.6 on April 5, 1990.
- Magnitude
- 6.3
- Strong · mw
- Depth
- 16 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: 100 km aftershock search area
In context
How big was it, and why here?
Energy released
43 kilotons of TNT
That is about 3 times the Hiroshima bomb. It released about 89 times the energy of a magnitude 5.0.
Tectonic setting
7 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
16 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 100 km
USGS lists 81 M2.5+ earthquakes within 100 km in the following 30 days; the largest was M5.3 on April 6, 1990. Most nearby activity right after a large earthquake is aftershocks, which usually become less frequent over days and weeks.
- 3.6229 km E of Saipan, Northern Mariana Islands36y ago · 56 km NE of this epicenter
- 4.8195 km ENE of Saipan, Northern Mariana Islands36y ago · 91 km N of this epicenter
- 4.7190 km E of Saipan, Northern Mariana Islands36y ago · 8 km W of this epicenter
- 4.5Mariana Islands region36y ago · 78 km NE of this epicenter
- 4.7194 km E of Saipan, Northern Mariana Islands36y ago · 3 km W of this epicenter
- 4.5199 km E of Saipan, Northern Mariana Islands36y ago · 3 km NE of this epicenter
- 4.6193 km E of Saipan, Northern Mariana Islands36y ago · 13 km SW of this epicenter
- 4.9Mariana Islands region36y ago · 17 km SW of this epicenter
Regional history
Past M5+ earthquakes within 300 km
USGS lists 194 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:
- 7.6198 km E of Saipan, Northern Mariana IslandsApril 5, 1990 · 6 km S of this epicenter
- 7.5Mariana Islands regionJanuary 17, 1940 · 224 km N of this epicenter
- 7.1233 km NE of Saipan, Northern Mariana IslandsJuly 2, 1949 · 151 km N of this epicenter
- 7.0176 km ESE of San Jose Village, Northern Mariana IslandsMay 18, 1913 · 116 km SW of this epicenter
- 7.0233 km ESE of Saipan, Northern Mariana IslandsJune 14, 1942 · 66 km SE of this epicenter
- 6.6Mariana Islands regionSeptember 1, 1970 · 283 km N of this epicenter
- 6.5258 km NE of Saipan, Northern Mariana IslandsDecember 1, 1938 · 212 km N of this epicenter
- 6.446 km ENE of Yigo Village, GuamOctober 29, 1936 · 298 km SW 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:
- 1990M7.5
Saipan; Guam
5 Apr 1990 · 6 km away · intensity IV
tsunami
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.