M3.7 earthquake 77 km N of Isangel, Vanuatu

Friday, November 21, 2008, 16:45:48 UTC · 18.842°S, 169.230°E

A magnitude 3.7 earthquake struck 77 km N of Isangel, Vanuatu on Friday, November 21, 2008, 16:45:48 UTC, at a depth of 230.2 km (intermediate).

Magnitude: 3.7; Minor · mb
Depth: 230 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: 50 km aftershock search area

In context

How big was it, and why here?

Energy released

5 tons of TNT

That is about 1/2,814 of the Hiroshima bomb. A magnitude 5.0 releases about 89 times more energy.

Tectonic setting

160 km

from the nearest mapped plate boundary, between the New Hebrides and Australian plates. Earthquakes this far from a boundary happen on faults inside a plate, often less frequently but sometimes strongly.

Depth: intermediate

230 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 50 km

USGS lists 5 M2.5+ earthquakes within 50 km in the following 30 days; the largest was M4.6 on December 5, 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 1,144 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 30 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700, which together caused about 36 recorded deaths. The most severe:

1875M8.1
Loyalty Islands: Lifou Island
28 Mar 1875 · 150 km away
26 deathsSevere damage ($5–24M)tsunami
1999M7.5
Pentecost
26 Nov 1999 · 290 km away
10 deathsSevere damage ($5–24M)tsunami
1920M8.1
Loyalty Islands
20 Sep 1920 · 149 km away
Limited damage (under $1M)tsunami
1878M7.5
Tanna Island
10 Jan 1878 · 79 km away
Limited damage (under $1M)tsunami
1961M7.3
Vanuatu Islands
23 Jul 1961 · 98 km away · intensity VI
Limited damage (under $1M)tsunami
2002M7.2
Efate, Port Vila
2 Jan 2002 · 200 km away
Limited damage (under $1M)tsunami

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

Nearby trackers