M7.3 earthquake 71 km SW of Isangel, Vanuatu

Wednesday, April 9, 2008, 12:46:12 UTC · 20.071°S, 168.892°E

A magnitude 7.3 earthquake struck 71 km SW of Isangel, Vanuatu on Wednesday, April 9, 2008, 12:46:12 UTC, at a depth of 33.0 km (shallow). It is the strongest earthquake within 300 km since an M7.3 on December 27, 2003.

Magnitude: 7.3; Major · mwc
Depth: 33 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

1.3 megatons of TNT

That is about 89 times the Hiroshima bomb. It released about 2,818 times the energy of a magnitude 5.0.

Tectonic setting

64 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 128 M2.5+ earthquakes within 200 km in the following 30 days; the largest was M6.4 on April 28, 2008. Most nearby activity right after a large earthquake is aftershocks, which usually become less frequent over days and weeks.

Time after the mainshock on a logarithmic scale (first hours stretched), magnitude on the vertical axis. M2.5+ events from USGS.

Regional history

Past M5+ earthquakes within 300 km

USGS lists 1,199 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:

History · NOAA

Deadliest earthquakes in this area

NOAA’s significant-earthquake database lists 31 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 · 42 km away
26 deathsSevere damage ($5–24M)tsunami
1901M7.9
Loyalty Islands
9 Aug 1901 · 243 km away
Moderate damage ($1–5M)tsunami
1920M8.1
Loyalty Islands
20 Sep 1920 · 44 km away
Limited damage (under $1M)tsunami
1878M7.5
Tanna Island
10 Jan 1878 · 126 km away
Limited damage (under $1M)tsunami
1961M7.3
Vanuatu Islands
23 Jul 1961 · 190 km away · intensity VI
Limited damage (under $1M)tsunami
2002M7.2
Efate, Port Vila
2 Jan 2002 · 296 km away
Limited damage (under $1M)tsunami

NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.

Nearby trackers