QuakeScout
Magnitude4.6

Reviewed by USGS29y ago

M4.6 earthquake in Fiji region

Sunday, March 23, 1997, 03:05:56 UTC · 20.733°S, 178.352°W

A magnitude 4.6 earthquake struck in Fiji region on Sunday, March 23, 1997, 03:05:56 UTC, at a depth of 572.5 km (deep). It is the strongest earthquake within 300 km since an M4.7 on March 17, 1997.

Magnitude
4.6
Light · mb
Depth
573 km
Deep
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

120 tons of TNT

That is about 1/126 of the Hiroshima bomb. A magnitude 5.0 releases about 4 times more energy.

Tectonic setting

215 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

573 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

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 4 M2.5+ earthquakes within 50 km in the following 30 days; the largest was M4.4 on March 28, 1997. Most nearby activity right after a large earthquake is aftershocks, which usually become less frequent over days and weeks.

M3M41h6h1d3d7d14d30dMainshock M4.6
Time after the mainshock on a logarithmic scale (first hours stretched), magnitude on the vertical axis. M2.5+ events from USGS.
  1. 4.2Fiji region29y ago · 48 km NW of this epicenter
  2. 4.4Fiji region29y ago · 41 km SW of this epicenter
  3. 4.3Fiji region29y ago · 7 km E of this epicenter
  4. 3.9Fiji region29y ago · 46 km NW of this epicenter

Regional history

Past M5+ earthquakes within 300 km

USGS lists 967 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:

  1. 7.8159 km W of Pangai, TongaDecember 14, 1950 · 283 km NE of this epicenter
  2. 7.8Fiji regionJanuary 1, 1919 · 160 km N of this epicenter
  3. 7.6178 km E of Levuka, FijiFebruary 22, 1909 · 291 km N of this epicenter
  4. 7.6240 km E of Levuka, FijiMarch 9, 1994 · 300 km N of this epicenter
  5. 7.5262 km WNW of Haveluloto, TongaMay 21, 1962 · 117 km NE of this epicenter
  6. 7.4Fiji regionSeptember 28, 1957 · 21 km N of this epicenter
  7. 7.4Fiji regionAugust 5, 1996 · 6 km NE of this epicenter
  8. 7.3227 km WNW of Haveluloto, TongaApril 16, 1937 · 109 km E of this epicenter

History · NOAA

Deadliest earthquakes in this area

NOAA’s significant-earthquake database lists 7 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 · 164 km away

  2. 1919M7.8

    Fiji Islands

    1 Jan 1919 · 160 km away

    tsunami

  3. 1950M7.7

    Tonga Islands

    14 Dec 1950 · 281 km away · intensity VI

  4. 1997M7.7

    Tonga Islands

    14 Oct 1997 · 223 km away

    tsunami

  5. 1994M7.6

    Fiji Islands

    9 Mar 1994 · 300 km away

  6. 1957M7.5

    Fiji Islands

    28 Sep 1957 · 40 km away

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

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