Reviewed by USGS40y ago
M4.9 earthquake in Mariana Islands region
Wednesday, September 17, 1986, 03:44:57 UTC · 19.574°N, 146.510°E
A magnitude 4.9 earthquake struck in Mariana Islands region on Wednesday, September 17, 1986, 03:44:57 UTC, at a depth of 33.0 km (shallow). It is the strongest earthquake within 300 km since an M5.1 on September 16, 1986.
- Magnitude
- 4.9
- Light · mb
- Depth
- 33 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: 50 km aftershock search area
In context
How big was it, and why here?
Energy released
338 tons of TNT
That is about 1/45 of the Hiroshima bomb. A magnitude 5.0 releases about 1 times more energy.
Tectonic setting
99 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
33 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 50 km
USGS lists 1 M2.5+ earthquake within 50 km in the following 30 days; the largest was M4.8 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 160 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 · 182 km SE of this epicenter
- 7.2Pagan region, Northern Mariana IslandsOctober 24, 1930 · 127 km S of this epicenter
- 7.2Mariana Islands regionJune 19, 1947 · 247 km NW of this epicenter
- 7.0Mariana Islands regionJune 13, 1947 · 267 km NW of this epicenter
- 6.9Maug Islands region, Northern Mariana IslandsMarch 7, 1962 · 153 km W of this epicenter
- 6.7Pagan region, Northern Mariana IslandsNovember 15, 1954 · 104 km SW of this epicenter
- 6.7Pagan region, Northern Mariana IslandsFebruary 1, 1956 · 180 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 · 183 km away · intensity IX
Severe damage ($5–24M)
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.