QuakeScout
Magnitude7.6

Reviewed by USGSNew Zealand80y ago

M7.6 earthquake 82 km ENE of Gisborne, New Zealand

Saturday, May 17, 1947, 07:06:41 UTC · 38.445°S, 178.909°E

A magnitude 7.6 earthquake struck 82 km ENE of Gisborne, New Zealand on Saturday, May 17, 1947, 07:06:41 UTC, at a depth of 25.0 km (shallow). It is the strongest earthquake within 300 km since an M7.7 on March 25, 1947.

Magnitude
7.6
Major · mw
Depth
25 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

3.5 megatons of TNT

That is about 235 times the Hiroshima bomb. It released about 7,413 times the energy of a magnitude 5.0.

Tectonic setting

41 km

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

Depth: shallow

25 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 200 km

USGS has not published any M2.5+ earthquake within 200 km in the 30 days after this event.

Regional history

Past M5+ earthquakes within 300 km

USGS lists 24 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:

  1. 7.746 km E of Gisborne, New ZealandMarch 25, 1947 · 42 km SW of this epicenter
  2. 7.447 km WSW of Hastings, New ZealandFebruary 2, 1931 · 266 km SW of this epicenter
  3. 7.340 km E of Waiouru, New ZealandFebruary 13, 1931 · 264 km SW of this epicenter
  4. 7.044 km N of Whakatane, New ZealandNovember 22, 1914 · 201 km NW of this epicenter
  5. 6.962 km S of Gisborne, New ZealandSeptember 15, 1932 · 112 km SW of this epicenter
  6. 6.75 km SSW of Hastings, New ZealandJune 28, 1921 · 226 km SW of this epicenter
  7. 6.748 km ENE of Opotiki, New ZealandOctober 6, 1914 · 111 km NW of this epicenter
  8. 6.6off the east coast of the North Island of New ZealandFebruary 13, 1938 · 284 km N 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 262 recorded deaths. The most severe:

  1. 1931M7.7

    Hawke Bay

    2 Feb 1931 · 289 km away · intensity IX

    261 deaths$25 million damagetsunami

  2. 1914

    North Island

    6 Oct 1914 · 95 km away · intensity VIII

    1 deathModerate damage ($1–5M)tsunami

  3. 1932M6.8

    Gisborne, Wairoa

    15 Sep 1932 · 137 km away

    Moderate damage ($1–5M)tsunami

  4. 1947M7.1

    Off Coast North Island

    25 Mar 1947 · 45 km away · intensity IV

    Limited damage (under $1M)tsunami

  5. 1904M7.5

    E Of North Island

    8 Aug 1904 · 281 km away

    tsunami

  6. 1931M7.1

    N

    13 Feb 1931 · 202 km away

    tsunami

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

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