M4.7 earthquake 220 km S of ‘Ohonua, Tonga

Sunday, April 19, 2009, 23:15:48 UTC · 23.320°S, 174.770°W

A magnitude 4.7 earthquake struck 220 km S of ‘Ohonua, Tonga on Sunday, April 19, 2009, 23:15:48 UTC, at a depth of 74.1 km (intermediate). It is the strongest earthquake within 300 km since an M4.7 on April 15, 2009.

Magnitude: 4.7; Light · mb
Depth: 74 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 earthquake

In context

How big was it, and why here?

Energy released

169 tons of TNT

That is about 1/89 of the Hiroshima bomb. A magnitude 5.0 releases about 3 times more energy.

Tectonic setting

4 km

from the nearest mapped plate boundary, between the Tonga and Pacific plates. Earthquakes cluster along boundaries like this one, where plates collide, pull apart or slide past each other.

Depth: intermediate

74 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 has not published any M2.5+ earthquake within 50 km in the 30 days after this event.

Regional history

Past M5+ earthquakes within 300 km

USGS lists 1,117 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 10 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700, which together caused about 1 recorded deaths. The most severe:

1977M7.2
Tonga Trench
22 Jun 1977 · 126 km away · intensity IV
1 death$1 million damagetsunami
1948M7.9
Tonga Islands
8 Sep 1948 · 270 km away
tsunami
1975M7.8
S Of Tonga
11 Oct 1975 · 179 km away
1982M7.7
Tonga Trench
19 Dec 1982 · 143 km away
tsunami
1997M7.7
Tonga Islands
14 Oct 1997 · 246 km away
tsunami
2009M7.6
Tonga Islands
19 Mar 2009 · 33 km away
tsunami

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

Nearby trackers