Reviewed by USGSVanuatu66y ago
M7.3 earthquake 63 km S of Port-Vila, Vanuatu
Sunday, July 23, 1961, 21:51:09 UTC · 18.307°S, 168.290°E
A magnitude 7.3 earthquake struck 63 km S of Port-Vila, Vanuatu on Sunday, July 23, 1961, 21:51:09 UTC, at a depth of 25.0 km (shallow). It is the strongest earthquake within 300 km since an M7.9 on December 2, 1950.
- Magnitude
- 7.3
- Major · mw
- Depth
- 25 km
- Shallow
- Felt reports
- 0
- Did You Feel It?
- Est. shaking
- VI
- Strong (ShakeMap)
- PAGER alert
- None
- Not issued
- Tsunami
- No flag
- USGS feed
Outlined circle: this earthquakeDashed circle: 200 km aftershock search areaColoured lines: estimated shaking intensity (USGS ShakeMap)
In context
How big was it, and why here?
Energy released
1.5 megatons of TNT
That is about 99 times the Hiroshima bomb. It released about 3,126 times the energy of a magnitude 5.0.
Tectonic setting
87 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
25 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 M5.9 on July 28, 1961. 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 116 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:
- 8.11920 Vanuatu EarthquakeSeptember 20, 1920 · 187 km S of this epicenter
- 7.999 km SW of Port-Vila, VanuatuDecember 2, 1950 · 68 km W of this epicenter
- 7.828 km ESE of Isangel, VanuatuJune 16, 1910 · 195 km SE of this epicenter
- 7.663 km NW of Isangel, VanuatuOctober 14, 1913 · 109 km SE of this epicenter
- 7.447 km WSW of Norsup, VanuatuNovember 9, 1910 · 264 km NW of this epicenter
- 7.247 km NNW of Isangel, VanuatuNovember 24, 1944 · 131 km SE of this epicenter
- 7.262 km NE of Isangel, VanuatuJuly 2, 1953 · 166 km SE of this epicenter
- 7.2113 km SSE of Port-Vila, VanuatuMarch 22, 1925 · 56 km SE of this epicenter
History · NOAA
Deadliest earthquakes in this area
NOAA’s significant-earthquake database lists 23 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700, which together caused about 26 recorded deaths. The most severe:
- 1875M8.1
Loyalty Islands: Lifou Island
28 Mar 1875 · 190 km away
26 deathsSevere damage ($5–24M)tsunami
- 1920M8.1
Loyalty Islands
20 Sep 1920 · 187 km away
Limited damage (under $1M)tsunami
- 1878M7.5
Tanna Island
10 Jan 1878 · 80 km away
Limited damage (under $1M)tsunami
- 1961M7.3
Vanuatu Islands
23 Jul 1961 · 18 km away · intensity VI
Limited damage (under $1M)tsunami
- 1933M6.4
Malekula
19 Nov 1933 · 166 km away
Limited damage (under $1M)tsunami
- 1913M8.1
Vanuatu Islands
14 Oct 1913 · 152 km away
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.