QuakeScout
Magnitude4.7

Reviewed by USGSSamoa17y ago

M4.7 earthquake 127 km SSW of Gataivai, Samoa

Friday, November 20, 2009, 07:49:30 UTC · 14.749°S, 173.010°W

A magnitude 4.7 earthquake struck 127 km SSW of Gataivai, Samoa on Friday, November 20, 2009, 07:49:30 UTC, at a depth of 26.8 km (shallow). It is the strongest earthquake within 300 km since an M4.9 on November 15, 2009.

Magnitude
4.7
Light · mb
Depth
27 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 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

9 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

27 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 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 1,203 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:

  1. 8.12009 Samoa EarthquakeSeptember 29, 2009 · 128 km SE of this epicenter
  2. 8.0The 1917 Samoa-Tonga EarthquakeJune 26, 1917 · 39 km SW of this epicenter
  3. 7.8146 km ESE of Hihifo, TongaDecember 26, 1975 · 178 km S of this epicenter
  4. 7.7133 km NE of Hihifo, TongaSeptember 1, 1981 · 25 km S of this epicenter
  5. 7.6199 km ESE of Hihifo, TongaApril 2, 1977 · 238 km SE of this epicenter
  6. 7.488 km NNE of Hihifo, TongaApril 7, 1995 · 75 km SW of this epicenter
  7. 7.2117 km SSW of Hihifo, TongaJanuary 8, 2000 · 276 km SW of this epicenter
  8. 7.219 km ENE of Hihifo, TongaOctober 15, 1984 · 141 km SW of this epicenter

History · NOAA

Deadliest earthquakes in this area

NOAA’s significant-earthquake database lists 8 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700, which together caused about 194 recorded deaths. The most severe:

  1. 2009M8.1

    Samoa Islands

    29 Sep 2009 · 128 km away

    192 deaths$285 million damagetsunami

  2. 1917M8.3

    Samoa Islands

    26 Jun 1917 · 84 km away

    2 deathsModerate damage ($1–5M)tsunami

  3. 1981M7.7

    Apia; American Samoa: Pago Pago

    1 Sep 1981 · 25 km away · intensity VI

    Limited damage (under $1M)tsunami

  4. 1977M7.6

    Apia

    2 Apr 1977 · 238 km away · intensity VI

    Limited damage (under $1M)tsunami

  5. 1975M7.8

    Samoa Islands

    26 Dec 1975 · 178 km away · intensity V

    tsunami

  6. 1957M7.5

    Samoa Islands

    14 Apr 1957 · 84 km away

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

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