Reviewed by USGS40y ago
M5.1 earthquake in Mariana Islands region
Tuesday, September 16, 1986, 18:56:32 UTC · 19.242°N, 146.347°E
A magnitude 5.1 earthquake struck in Mariana Islands region on Tuesday, September 16, 1986, 18:56:32 UTC, at a depth of 74.1 km (intermediate). It is the strongest earthquake within 300 km since an M6.7 on September 16, 1986.
- Magnitude
- 5.1
- Moderate · mb
- Depth
- 74 km
- Intermediate
- 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: 75 km aftershock search area
In context
How big was it, and why here?
Energy released
674 tons of TNT
That is about 1/22 of the Hiroshima bomb. It released about 1 times the energy of a magnitude 5.0.
Tectonic setting
127 km
from the nearest mapped plate boundary, between the Mariana and Pacific plates. Earthquakes this far from a boundary happen on faults inside a plate, often less frequently but sometimes strongly.
Depth: intermediate
74 km
Intermediate-depth earthquakes usually break inside a plate that is sinking into the mantle. Shaking spreads over a wide area but is gentler at the epicenter than a shallow quake of the same size.
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 75 km
USGS lists 2 M2.5+ earthquakes within 75 km in the following 30 days; the largest was M4.9 on September 17, 1986. 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 169 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 · 165 km SE of this epicenter
- 7.5Mariana Islands regionJanuary 17, 1940 · 296 km SE of this epicenter
- 7.2Pagan region, Northern Mariana IslandsOctober 24, 1930 · 95 km S of this epicenter
- 7.2Mariana Islands regionJune 19, 1947 · 275 km N of this epicenter
- 7.0Mariana Islands regionJune 13, 1947 · 296 km N of this epicenter
- 6.9Maug Islands region, Northern Mariana IslandsMarch 7, 1962 · 127 km W of this epicenter
- 6.7Pagan region, Northern Mariana IslandsNovember 15, 1954 · 68 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:
- 1902M8.1
Agana
22 Sep 1902 · 143 km away · intensity IX
Severe damage ($5–24M)
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.