Reviewed by USGS45y ago
M7.0 earthquake southeast of the Loyalty Islands
Monday, July 6, 1981, 03:08:24 UTC · 22.293°S, 171.742°E
A magnitude 7.0 earthquake struck southeast of the Loyalty Islands on Monday, July 6, 1981, 03:08:24 UTC, at a depth of 33.0 km (shallow). It is the strongest earthquake within 300 km since an M7.2 on October 25, 1980.
- Magnitude
- 7.0
- Major · ms
- 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: 200 km aftershock search area
In context
How big was it, and why here?
Energy released
477 kilotons of TNT
That is about 32 times the Hiroshima bomb. It released about 1,000 times the energy of a magnitude 5.0.
Tectonic setting
93 km
from the nearest mapped plate boundary, between the New Hebrides and Australian 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 200 km
USGS lists 2 M2.5+ earthquakes within 200 km in the following 30 days; the largest was M4.7 on July 28, 1981. 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 314 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:
- 7.6274 km ESE of Tadine, New CaledoniaMarch 16, 1928 · 139 km W of this epicenter
- 7.2southeast of the Loyalty IslandsNovember 14, 1906 · 30 km SW of this epicenter
- 7.2207 km E of Tadine, New CaledoniaOctober 25, 1980 · 200 km W of this epicenter
- 7.1southeast of the Loyalty IslandsAugust 17, 1935 · 28 km W of this epicenter
- 7.1southeast of the Loyalty IslandsApril 14, 1906 · 43 km W of this epicenter
- 7.1175 km SE of Isangel, VanuatuMarch 30, 1910 · 222 km NW of this epicenter
- 7.0southeast of the Loyalty IslandsAugust 25, 1926 · 102 km SE of this epicenter
History · NOAA
Deadliest earthquakes in this area
NOAA’s significant-earthquake database lists 4 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700. The most severe:
- 1901M7.9
Loyalty Islands
9 Aug 1901 · 182 km away
Moderate damage ($1–5M)tsunami
- 1928M7.5
Loyalty Islands
16 Mar 1928 · 132 km away
- 1943M7.5
Loyalty Islands
14 Sep 1943 · 83 km away
- 1944M7.5
Loyalty Islands
5 Oct 1944 · 35 km away
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.