QuakeScout
Magnitude4.9

Reviewed by USGSNew Zealand50y ago

M4.9 earthquake in Kermadec Islands, New Zealand

Thursday, August 19, 1976, 01:33:55 UTC · 30.367°S, 177.750°W

A magnitude 4.9 earthquake struck in Kermadec Islands, New Zealand on Thursday, August 19, 1976, 01:33:55 UTC, at a depth of 33.0 km (shallow). It is the strongest earthquake within 300 km since an M5.3 on August 19, 1976.

Magnitude
4.9
Light · mb
Depth
33 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

338 tons of TNT

That is about 1/45 of the Hiroshima bomb. A magnitude 5.0 releases about 1 times more energy.

Tectonic setting

106 km

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

Depth: shallow

33 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 3 M2.5+ earthquakes within 50 km in the following 30 days; the largest was M5.8 on August 19, 1976. Most nearby activity right after a large earthquake is aftershocks, which usually become less frequent over days and weeks.

M3M4M5M61h6h1d3d7d14d30dMainshock M4.9
Time after the mainshock on a logarithmic scale (first hours stretched), magnitude on the vertical axis. M2.5+ events from USGS.
  1. 5.5Kermadec Islands, New Zealand50y ago · 36 km NW of this epicenter
  2. 5.4Kermadec Islands, New Zealand50y ago · 46 km NW of this epicenter
  3. 5.8Kermadec Islands, New Zealand50y ago · 38 km E of this epicenter

Regional history

Past M5+ earthquakes within 300 km

USGS lists 394 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:

  1. 8.21917 Kermadec Islands, New Zealand EarthquakeMay 1, 1917 · 139 km SE of this epicenter
  2. 8.01976 Kermadec Islands, New Zealand EarthquakeJanuary 14, 1976 · 216 km N of this epicenter
  3. 7.5Kermadec Islands, New ZealandNovember 16, 1917 · 58 km N of this epicenter
  4. 7.3Kermadec Islands regionSeptember 14, 1959 · 178 km N of this epicenter
  5. 7.3Kermadec Islands, New ZealandMarch 26, 1963 · 42 km N of this epicenter
  6. 7.3Kermadec Islands, New ZealandJuly 25, 1968 · 61 km SW of this epicenter
  7. 7.2Kermadec Islands regionJuly 2, 1974 · 225 km NE of this epicenter
  8. 7.2Kermadec Islands, New ZealandAugust 2, 1941 · 67 km N 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. 1976M7.9

    Kermadec Islands

    14 Jan 1976 · 134 km away

    Limited damage (under $1M)tsunami

  2. 1968M7.3

    S Of, Raoul

    25 Jul 1968 · 79 km away

    Limited damage (under $1M)tsunami

  3. 1917M8.0

    Kermadec Islands

    1 May 1917 · 149 km away

    tsunami

  4. 1976M7.8

    Kermadec Islands

    14 Jan 1976 · 71 km away · intensity VIII

  5. 1959M7.7

    Kermadec Islands

    14 Sep 1959 · 220 km away

  6. 1943M7.6

    S Of

    14 Sep 1943 · 83 km away

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

Nearby trackers

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