QuakeScout
Magnitude7.3

Reviewed by USGS15y ago

M7.3 earthquake in Fiji region

Thursday, September 15, 2011, 19:31:04 UTC · 21.611°S, 179.528°W

A magnitude 7.3 earthquake struck in Fiji region on Thursday, September 15, 2011, 19:31:04 UTC, at a depth of 644.6 km (deep). USGS received 9 “Did You Feel It?” reports, with a maximum reported intensity of II (weak). It is the strongest earthquake within 300 km since an M7.7 on August 19, 2002.

Magnitude
7.3
Major · mww
Depth
645 km
Deep
Felt reports
9
Max intensity II
Est. shaking
—
No ShakeMap
PAGER alert
None
Not issued
Tsunami
No flag
USGS feed

Outlined circle: this earthquakeDashed circle: 200 km aftershock search area

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

303 km

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

Depth: deep

645 km

Deep earthquakes (over 300 km) happen deep inside subducting plates. They rarely cause damage, but can be felt faintly over very large distances.

Did You Feel It?

Where it was felt

9 people reported feeling this earthquake to USGS; a per-place breakdown is not available 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 4 M2.5+ earthquakes within 200 km in the following 30 days; the largest was M4.9 on October 1, 2011. Most nearby activity right after a large earthquake is aftershocks, which usually become less frequent over days and weeks.

M3M4M5M6M71h6h1d3d7d14d30dMainshock M7.3
Time after the mainshock on a logarithmic scale (first hours stretched), magnitude on the vertical axis. M2.5+ events from USGS.
  1. 4.9248 km S of Levuka, Fiji15y ago · 185 km NW of this epicenter
  2. 4.2south of the Fiji Islands15y ago · 109 km S of this epicenter
  3. 4.7Fiji region15y ago · 26 km E of this epicenter
  4. 4.7Fiji region15y ago · 132 km N of this epicenter

Regional history

Past M5+ earthquakes within 300 km

USGS lists 1,230 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:

  1. 7.8Fiji regionJanuary 1, 1919 · 296 km NE of this epicenter
  2. 7.8192 km WSW of Haveluloto, TongaOctober 14, 1997 · 290 km E of this epicenter
  3. 7.7Fiji regionAugust 19, 2002 · 10 km S of this epicenter
  4. 7.5262 km WNW of Haveluloto, TongaMay 21, 1962 · 274 km NE of this epicenter
  5. 7.4Fiji regionSeptember 28, 1957 · 171 km NE of this epicenter
  6. 7.4Fiji regionAugust 5, 1996 · 163 km NE of this epicenter
  7. 7.3227 km WNW of Haveluloto, TongaApril 16, 1937 · 256 km NE of this epicenter
  8. 7.3Fiji regionMay 25, 1944 · 10 km E of this epicenter

History · NOAA

Deadliest earthquakes in this area

NOAA’s significant-earthquake database lists 5 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700. The most severe:

  1. 1937M8.1

    Fiji Islands

    16 Apr 1937 · 262 km away

  2. 1919M7.8

    Fiji Islands

    1 Jan 1919 · 296 km away

    tsunami

  3. 1997M7.7

    Tonga Islands

    14 Oct 1997 · 290 km away

    tsunami

  4. 2002M7.7

    Fiji Islands

    19 Aug 2002 · 10 km away

  5. 1957M7.5

    Fiji Islands

    28 Sep 1957 · 172 km away

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

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