QuakeScout
Magnitude4.7

Reviewed by USGSTonga17y ago

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

Wednesday, April 15, 2009, 20:26:24 UTC · 23.323°S, 175.056°W

A magnitude 4.7 earthquake struck 220 km S of ‘Ohonua, Tonga on Wednesday, April 15, 2009, 20:26:24 UTC, at a depth of 60.1 km (shallow). It is the strongest earthquake within 300 km since an M4.9 on April 7, 2009.

Magnitude
4.7
Light · mb
Depth
60 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: 50 km aftershock search area

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

29 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: shallow

60 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 50 km

USGS lists 1 M2.5+ earthquake within 50 km in the following 30 days; the largest was M4.7 on April 19, 2009. Most nearby activity right after a large earthquake is aftershocks, which usually become less frequent over days and weeks.

M3M4M51h6h1d3d7d14d30dMainshock M4.7
Time after the mainshock on a logarithmic scale (first hours stretched), magnitude on the vertical axis. M2.5+ events from USGS.
  1. 4.7220 km S of ‘Ohonua, Tonga17y ago · 29 km E of this epicenter

Regional history

Past M5+ earthquakes within 300 km

USGS lists 1,129 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:

  1. 7.8south of TongaOctober 11, 1975 · 175 km S of this epicenter
  2. 7.8192 km WSW of Haveluloto, TongaOctober 14, 1997 · 222 km NW of this epicenter
  3. 7.6south of the Fiji IslandsDecember 18, 1963 · 241 km SW of this epicenter
  4. 7.6191 km S of ‘Ohonua, TongaMarch 19, 2009 · 51 km NE of this epicenter
  5. 7.5110 km E of ‘Ohonua, TongaSeptember 8, 1948 · 263 km NE of this epicenter
  6. 7.4south of TongaMarch 18, 1905 · 204 km SE of this epicenter
  7. 7.2south of the Fiji IslandsNovember 24, 1960 · 193 km SW of this epicenter
  8. 7.2south of TongaOctober 10, 1977 · 284 km S of this epicenter

History · NOAA

Deadliest earthquakes in this area

NOAA’s significant-earthquake database lists 12 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700, which together caused about 1 recorded deaths. The most severe:

  1. 1977M7.2

    Tonga Trench

    22 Jun 1977 · 99 km away · intensity IV

    1 death$1 million damagetsunami

  2. 1937M8.1

    Fiji Islands

    16 Apr 1937 · 285 km away

  3. 1948M7.9

    Tonga Islands

    8 Sep 1948 · 280 km away

    tsunami

  4. 1975M7.8

    S Of Tonga

    11 Oct 1975 · 175 km away

  5. 1982M7.7

    Tonga Trench

    19 Dec 1982 · 122 km away

    tsunami

  6. 1997M7.7

    Tonga Islands

    14 Oct 1997 · 222 km away

    tsunami

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

Nearby trackers

Closest city pages